DOT/FAA/AR-05/23 

Office of Aviation Research 

Washington, D.C. 20591

Development of a Reference 

Liquid Water Content Probe 

August 2005 

Final Report 

This document is available to the U.S. public 

through the National Technical Information 

Service (NTIS), Springfield, Virginia 22161. 

U.S. Department of Transportation 

Federal Aviation Administration
NOTICE 

This document is disseminated under the sponsorship of the U.S. 

Department of Transportation in the interest of information exchange. The 

United States Government assumes no liability for the contents or use 

thereof. The United States Government does not endorse products or 

manufacturers. Trade or manufacturer's names appear herein solely 

because they are considered essential to the objective of this report. This 

document does not constitute FAA certification policy. Consult your local 

FAA aircraft certification office as to its use. 

This report is available at the Federal Aviation Administration William J. 

Hughes Technical Center's Full-Text Technical Reports page: 

actlibrary.tc.faa.gov in Adobe Acrobat portable document format (PDF). 
 Technical Report Documentation Page

1. Report No.

DOT/FAA/AR-05/23

2. Government Accession No. 3. Recipient's Catalog No.

5. Report Date 

August 2005

 4. Title and Subtitle 

DEVELOPMENT OF A REFERENCE LIQUID WATER CONTENT PROBE 

6. Performing Organization Code

7. Author(s)

J. Tan, M. Papadakis, and S. Muthuswamy 

8. Performing Organization Report No. 

10. Work Unit No. (TRAIS) 

 

9. Performing Organization Name and Address

Department of Aerospace Engineering 

Wichita State University 

Wichita, KS 67260

11. Contract or Grant No.

 12. Sponsoring Agency Name and Address

U.S. Department of Transportation 

Federal Aviation Administration

13. Type of Report and Period Covered

 Final Report

Office of Aviation Research 

Washington, DC 20591

14. Sponsoring Agency Code

 AIR-100

15. Supplementary Notes 

The FAA William J. Hughes Technical Center Technical Monitor was Manny Rios. 16. Abstract 

This study reports on the development and calibration of a proof-of-concept reference probe for measuring the liquid water 

content (LWC) as defined in Title 14 Code of Federal Regulations Part 25, Appendix C and in supercooled large droplet icing 

cloud conditions. The conceptual design was based on a total pressure probe, water collector, and suction fan. Water droplets

were collected iso-kinetically by the probe and weighed to determine the LWC. The initial effort concentrated on the evaluation 

of different methods of capturing and storing water droplets that entered the probe. Different types of adsorbent materials were 

installed into a detachable water collector to remove water droplets from an ingress water cloud via adsorption, e.g., with water 

adsorbent and blotter papers, silica gel and molecular sieve desiccants, and hydrophobic B-Gon fiber mesh. The basic test 

methodology was to inject a known amount of water directly into the probe inlet and then compare this to the amount adsorbed by

the water collector. Tests conducted in a laboratory showed that collection efficiencies of 100.8 ±8% for LWC between 0.5 and 

3.0g/m3

 were obtainable with the water collector configuration 11 Mod-I design. This design used a combination of blotter paper, 

silica gel, and B-Gon fiber to adsorb and trap incoming water droplets. However, silica gel desiccants adsorb ambient moisture

(as well as water droplets from the spray cloud) that is difficult to quantify; therefore, the test data contained some measurement 

errors. In order to overcome this problem, the silica gel desiccant was removed from the Mod-I design, and instead, the ambient 

moisture was measured with an accurate humidity sensor, which was installed inside the probe. The modified probe was renamed 

the configuration 11 Mod-II design. Limited laboratory test results showed that collection efficiencies of 92 ±8% were obtainable 

with the Mod-II design. The iso-kinetic performance of the probe was successfully tested in the wind tunnel at velocities between 

105 and 130 mph, where the iso-kinetic condition was attained within 3 seconds of engaging the suction fan of the probe. In 

summary, the study has successfully demonstrated a proof-of-concept reference probe in a laboratory and wind tunnel. However, 

further developments are required before it can be used as a production probe to measure LWC in Appendix C and large median 

volumetric diameter spray clouds. 

17. Key Words 

Aircraft icing, Liquid water content probe, Iso-kinetic 

conditions 

18. Distribution Statement 

This document is available to the public through the National 

Technical Information Service (NTIS) Springfield, Virginia 

22161.

19. Security Classif. (of this report) 

 Unclassified

20. Security Classif. (of this page) 

 Unclassified

21. No. of Pages 

 135 

22. Price

Form DOT F1700.7 (8-72) Reproduction of completed page authorized
ACKNOWLEDGEMENTS 

This work was supported by a grant from the Federal Aviation Administration (FAA). The 

authors would like to thank Mr. Manny Rios and Dr. James T. Riley of the FAA William J. 

Hughes Technical Center; Mr. Eugene Hill, the FAA Icing National Resource Specialist; and 

Tom Bond, the Chief of the Icing Branch at the NASA Glenn Research Center for their support. 

The authors acknowledge the efforts of the following Wichita State University (WSU) personnel: 

Hsiung-Wei Yeong and the wind tunnel crew for their assistance with the wind tunnel tests; 

Mark Murrell and Art Porter of the WSU Machine Shop for their efforts in fabricating the probe. 

iii/iv
TABLE OF CONTENTS 

Page 

EXECUTIVE SUMMARY xiii 

1. INTRODUCTION 1-1 

2. DESIGN OF AN ISO-KINETIC PROBE 2-1 

2.1 Technical Design 2-2 

2.2 Probe Fabrication 2-4 

2.3 Computational Fluid Dynamics Analysis 2-7 

2.3.1 Computational Fluid Dynamics Simulation of the LWC Probe in a 

Wind Tunnel 2-7 

2.3.2 Computational Fluid Dynamics Simulation of the Water Collector 2-10 

3. EXPERIMENTAL INVESTIGATION IN A LABORATORY 3-1 

3.1 Experimental Setup 3-1 

3.2 Water-Adsorbent Materials 3-4 

3.3 Preliminary Tests 3-6 

3.4 Water Collector Configuration Tests 3-8 

3.5 Tests With Water Collector Configuration 11 Mod-I 3-20 

3.5.1 Findings 3-28 

3.5.2 Conclusions 3-28 

4. EXPERIMENTAL INVESTIGATION IN A WIND TUNNEL WITH THE WATER 

COLLECTOR CONFIGURATION 11 MOD-I DESIGN 4-1 

4.1 Test Facility 4-1 

4.2 Probe Installation 4-1 

4.3 Iso-Kinetic Flow Control System 4-3 

4.3.1 Throttling Valve 4-4 

4.3.2 The ISFC Software and Data Acquisition System 4-5 

4.4 Test Procedure 4-9 

4.5 Test Measurements 4-10 

4.6 Results and Discussions 4-14 

5. EXPERIMENTAL INVESTIGATION WITH THE WATER COLLECTOR 

CONFIGURATION 11 MOD-II DESIGN 5-1 

v
5.1 Method of Computing LWC With Relative Humidity Measurements 5-1 

5.2 Test Measurements 5-2 

5.3 Data Reduction 5-9 

5.4 Results and Discussion 5-11 

6. SUMMARY 6-1 

7. CONCLUSIONS 7-1 

8. RECOMMENDATIONS 8-1 

9. REFERENCES 9-1 

APPENDICES 

A—Characteristics of Silica Gel and Molecular Sieve Desiccants 

B—Water Collector Configuration Tests 

C—Test Procedure for Configuration 11 Mod-I 

D—Mod-I Test Data—Wind Tunnel 

E—Mod-II Test Data—Laboratory 

F—Fundamental Humidity Equations 

vi
LIST OF FIGURES 

Figure Page 

2-1 Schematic Layout of LWC Reference Probe in a Wind Tunnel 2-1 

2-2 Technical Drawing of the Reference Probe 2-3 

2-3 Sealing Joint DRGW 1 2-3 

2-4 Coannular Sectional View of the Water Collector 2-3 

2-5 Flange 2 2-4 

2-6 Flange 3 2-4 

2-7 Flange 4 2-4 

2-8 Flange 5 2-4 

2-9 Components of the Probe 2-4 

2-10 Probe Assembly 2-4 

2-11 Probe Inlet—Side View 2-5 

2-12 Probe Inlet—Bottom View 2-5 

2-13 Probe With Total and Static Ports 2-5 

2-14 Probe Main Body and Convergent Outlet Nozzle 2-6 

2-15 Coannular Water Collector Container 2-6 

2-16 Assembly of Water Collection System 2-6 

2-17 Computational Grid of the Wind Tunnel and Probe 2-8 

2-18 Solid Model of the Reference Probe 2-8 

2-19 Predicted Streamlines—Side View 2-9 

2-20 Predicted Velocity Vectors and Streamlines—Isometric View 2-9 

2-21 Predicted Velocity Vectors and Streamlines—Top View 2-9 

2-22 Computational Grid of the Reference Probe 2-10 

2-23 Predicted Velocity Vectors Inside the Probe 2-12 

vii
2-24 Streamlines Distribution Inside the Probe 2-12 

2-25 Velocity Contour Across Collector—Top View 2-12 

2-26 Pressure Distribution Across Collector—Top View 2-12 

2-27 Streamlines Distribution Inside Probe—Probe Main Body Removed 2-13 

2-28 Streamlines Distribution Inside Probe—Top View 2-13 

3-1 Experimental Setup 3-1 

3-2 Schematic Setup 3-1 

3-3 Aerodynamic Performance of Suction Fan 3-2 

3-4 Direct Method of Water Injection With the Spray Brush 3-3 

3-5 Water Collector Assembly 3-3 

3-6 Various Components of the Collector 3-3 

3-7 Method of Installing Silica Gel and Molecular Sieve 3-4 

3-8 Water-Adsorbent Paper Wrapped Around Inner Container 3-4 

3-9 B-Gon Wrapped Around Inner Container of Collector 3-4 

3-10 Blotter Paper Attached to the Divergent Nozzle 3-4 

3-11 Silica Gel 3-5 

3-12 Molecular Sieve 3-5 

3-13 DRIMOP 3-5 

3-14 B-Gon Fiber Mesh 3-5 

3-15 Water-Adsorbent Paper 3-6 

3-16 Blotter Paper 3-6 

3-17 Pressure Loss Devices With Three Different Opening Sizes 3-20 

3-18 Installation of a Pressure Loss Device Downstream of the Suction Fan 3-20 

3-19 Liquid Water Content (Water Collected) Versus LWC (Water Sprayed) 3-21 

3-20 Liquid Water Content (Water Collected) Versus Collection Efficiency 3-21 

viii
3-21 Contributions to Collection Efficiency by Blotter Paper and Silica Gel 3-21 

4-1 The WSU 7- by 10-ft Wind Tunnel Facility 4-1 

4-2 Installation of the Reference Probe in the WSU 7- by 10-ft Wind Tunnel— 

Front View 4-2 

4-3 Position of the Spray Brush in Front of the Probe Inlet 4-2 

4-4 Water Supply for the Spray Brush 4-2 

4-5 Humidity Sensor Vaisala 4-3 

4-6 Humidity Sensor Inside the Reference Probe 4-3 

4-7 Extension Hose Connects Probe to Suction Fan 4-3 

4-8 Suction Fan Exhaust to Throttle Valve 4-3 

4-9 Throttle Valve 4-4 

4-10 Probe Inlet Pressure Versus Valve Driving Current 4-4 

4-11 Data Acquisition System (SCXI-1001) 4-5 

4-12 Iso-Kinetic Flow Control Software 4-6 

4-13 Static Pressure Plots—Laboratory 4-8 

4-14 Relative Humidity Plots—Laboratory 4-8 

4-15 Temperature Plots—Laboratory 4-8 

4-16 Preparation of the Reference Probe and ISFC Control 4-10 

4-17 Comparison Between LWCs Based on Water Collected and Sprayed 4-11 

4-18 Liquid Water Content Versus Collection Efficiency 4-11 

4-19 Probe and Tunnel RH Distribution—Wind Tunnel in Operation 4-14 

4-20 Probe and Tunnel Temperature Distribution—Wind Tunnel in Operation 4-14 

4-21 Probe and Tunnel RH Distribution—Static Spray Test 4-15 

4-22 Probe and Tunnel Temperature Distribution—Static Spray Test 4-15 

4-23 Probe and Tunnel Pressure Distribution—Wind Tunnel in Operation 4-16 

ix
4-24 Probe and Tunnel Pressure Distribution—Static Spray Test 4-16 

5-1 Humidity Sensor Inside the Reference Probe 5-3 

5-2 Fisherbrand Humidity Sensor 5-3 

5-3 Throttle Valve Installed in a Fume Cupboard 5-3 

5-4 Iso-Kinetic Flow Control System 5-3 

5-5 Method of Creating a Multilayered Blotter Tube 5-4 

5-6 Comparison Between LWCs Based on Water Collected and Water Sprayed 5-4

5-7 Liquid Water Content Based on Water Collected Versus Collection Efficiency 5-4

5-8 Contribution to the LWC by Blotter, B-Gon, and Evaporated Water 5-5 

5-9 Distribution of Probe Volumetric Mass Flow Ratio 5-5 

5-10 Probe RH Distribution 5-10 

5-11 Probe Static Pressure Distribution 5-10 

5-12 Probe Temperature Distribution 5-10 

5-13 Static Pressure Distribution—Test 2 5-12 

5-14 Static Pressure Distribution—Test 7 5-12 

x
LIST OF TABLES 

Table Page 

3-1 Test Results for Configuration 1 3-9 

3-2 Test Results for Configuration 2 3-10 

3-3 Test Results for Configuration 3 3-11 

3-4 Test Results for Configuration 4 3-11 

3-5 Test Results for Configuration 5 3-12 

3-6 Test Results for Configuration 6 3-13 

3-7 Test Results for Configuration 7 3-13 

3-8 Test Results for Configuration 8 3-14 

3-9 Test Results for Configuration 9 3-15 

3-10 Test Results for Configuration 10 3-16 

3-11 Test Results for Configuration 11 3-17 

3-12 Test Results for Configuration 11 Mod-I 3-19 

3-13 Test Results for Configuration 11 Mod-I (Laboratory) 3-22 

4-1 Test Results for Configuration 11 Mod-I (Wind Tunnel) 4-12 

5-1 Test Results for Configuration 11 Mod-II (Laboratory) 5-6 

xi/xii
EXECUTIVE SUMMARY

A proof-of-concept reference probe was fabricated from Perspex and high-density molecular 

weight polyethylene material to demonstrate the iso-kinetic technique of measuring liquid water 

content (LWC) in Title 14 Code of Federal Regulations (CFR) Part 25 Appendix C and in 

supercooled large.droplet icing cloud. The probe consisted of a 90 degree elbow inlet, water 

collector, external main body, and suction fan. Tests were conducted in a laboratory and wind 

tunnel to assess the probe’s performance, such as the range of applicable LWC, tunnel velocities 

and water mass, and its measurement accuracy. The conceptual design was based on a total 

pressure probe that was connected to a water collector and suction fan. Iso-kinetic condition 

(i.e., capture area ratio of 1.0) was obtained by setting the static pressure at the probe inlet to the 

static pressure in the free stream. This was achieved by varying the volumetric flow rate through 

the probe with a metering valve so that the probe inlet velocity matched the tunnel free-stream 

velocity. Water droplets that entered the probe were collected in a removable container that was 

lined with water-adsorbent paper and desiccant material. The container was weighed (before and 

after a spray test) to determine the amount of water collected in a given duration. The LWC was 

determined from the collected water mass and volumetric air drawn into the probe. 

The initial effort concentrated on the selection of the best performing water collector 

configuration, based on its collection efficiency, which was carried out mainly in a laboratory. 

The method of assessment involved injecting a known amount of water in the form of a water 

droplet cloud directly into the probe and then compare this to the amount collected by the water 

collector. The ratio between these two measurements defines the collection efficiency for a 

particular water collector configuration. Tests conducted in a laboratory showed that collection 

efficiencies of 100.8 ±8% for LWC between 0.5 and 3.0g/m3

 were obtainable with the water 

collector configuration 11 Mod-I design. This design used a combination of blotter paper, silica 

gel, and B-Gon fiber to adsorb and trap incoming water droplets. Lower collection efficiencies 

were obtained in the (limited) tests conducted in the Wichita State University 7- by 10-ft wind 

tunnel. It is believed that the dry conditions in the wind tunnel led to excessive evaporative loss 

in the water collector, hence, the poor measurements. The temperatures (in the test section) were 

approximately 100o

F, and humidity ranged from 20% to 35%. The evaporative loss was detected 

with a humidity sensor that was installed inside the reference probe. However, the iso-kinetic 

performance of the probe was successfully tested in the wind tunnel at velocities between 105 

and 130 mph, where the (iso-kinetic) condition was attained within 3 seconds of engaging the 

suction fan of the probe. 

Although the conceptual workings of the Mod-I design was quite successful, there were some 

inherent measurement errors caused by the environment moisture that was adsorbed into the 

silica gel desiccant, which cannot be easily accounted for. To overcome this, the (silica gel) 

desiccant was removed from the Mod-I design, and instead, the ambient moisture was measured 

with an accurate humidity sensor that was installed inside the probe. The modified probe was 

renamed the configuration 11 Mod-II design. Limited laboratory tests showed that collection 

efficiencies of about 92 ±8% were obtained with the Mod-II design. The results were 

encouraging as it overcomes the significant drawback in the Mod-I design, and it provides a 

direct development path for converting this conceptual probe to a production design suitable for 

measuring LWC in 14 CFR Part 25 Appendix C and large MVD spray clouds.

xiii/xiv
1. INTRODUCTION. 

This work was part of an ongoing effort to develop instrumentation for total liquid water content 

(LWC) measurements in supercooled large droplet (SLD) icing conditions. SLD splashing 

effects pose significant problems for current instrumentation used for measuring LWC. The 

icing blade and rotating cylinder, which are commonly used to measure LWC in icing wind 

tunnels, can provide accurate measurements in an icing spray cloud with a median volume 

diameter (MVD) less than 50 microns. However, it was reported that their accuracies tend to 

degrade with increasing MVD spray cloud [1]. Hot-wire probes also showed significant drop-off 

in response with large MVD cloud; therefore, some measurements have been known to vary by 

more than 20% from the mean values [2]. Limited experimental data showed that large droplets 

tend to splash on impact with solid surfaces [3 and 4], and it is believed that some of the original 

water mass may have been lost from the process, hence, poorer LWC measurements. Since a 

significant proportion of the droplet sizes in an SLD icing cloud are greater than 50 microns, 

there is a concern that current LWC instruments may not be able to provide accurate LWC 

measurements. It is important that accurate measurements in icing tunnels can be obtained for 

SLD conditions due to the need to develop experimental data that is directly applicable to 

certification and also for developing and validating icing codes, which can adequately predict ice 

shapes in these conditions. 

To address this, a proof-of-concept iso-kinetic probe was developed to measure LWC in an SLD 

icing cloud. The advantage of an iso-kinetic probe is that it is less sensitive to droplet splashing; 

therefore, it can cope with large droplets or mixed-phase icing conditions. Unlike an icing blade 

or hot-wire LWC probes, droplets were drawn iso-kinetically into the probe and caught by a 

barrier filter. The amount (of water mass) collected was then weighed to provide a direct LWC 

measurement. The iso-kinetic condition defines a cylindrical stream tube in a spray cloud with a 

cross-sectional area equal to the probe’s inlet area, hence, each measurement represents a 

discrete point in a spray cloud distribution. This (iso-kinetic) condition was achieved by nulling 

(or simply equalizing) the wall static pressures between the flows inside and outside of the probe, 

hence, equal velocities prevailed (inside and outside of the probe) [5]. 

The development of the probe required a considerable effort; therefore, it was undertaken in the 

following phases: 

1. To construct and demonstrate the concept of iso-kinetic measurement of LWC. 

2. To compares the LWC measured by the reference probe and an existing LWC instrument 

in a wind tunnel. 

3. To fabricate a new airfoil-shaped reference probe suitable for wind tunnel. 

4. To assesses the probe’s performance in an icing wind tunnel. 

1-1
The current study included the following research steps:

• Conceptual design of the probe. 

• Computational fluid dynamics (CFD) analysis of the probe. 

• Fabrication and installation of the probe. 

• Evaluation of different water collection techniques using a range of water absorption and 

hydrophobic materials. 

• Selection of a collection technique and calibration tests in a laboratory. 

• Development of software and instrumentation for iso-kinetic measurement. 

• Testing in the Wichita State University (WSU) 7- by 10-ft wind tunnel. 

• Report preparation. 

This report describes the work performed and findings from the above steps. Significant 

effort was focused on the selection of an efficient water collector configuration in the icing 

laboratory. The method of assessment was based on the injection of a known amount of water 

directly into the probe and then measuring the amount collected by the water collector. The ratio 

between these two measurements defines the collection efficiency of the water collector. The 

water spray was created with a painter’s brush that was placed near the probe’s inlet nozzle. 

The iso-kinetic performance of the probe was evaluated in the WSU 7- by 10-ft wind tunnel. 

During the wind tunnel tests, a number of LWC measurements was also performed to 

evaluate the probe performance under more realistic conditions. 

The report is arranged in the following manner: 

• Section 1 introduces the topic of research and defines the needs for a probe that can 

accurately measure LWC in a SLD spray cloud. 

• Section 2 describes the design and fabrication of the conceptual reference probe. It 

also describes the CFD simulations of the conceptual probe in a wind tunnel and the 

flow distribution through the water collector inside the probe. 

• Section 3 describes the experimental tests that were conducted in a laboratory 

including 11 different water collector configurations. It also describes an extended 

test program with the selected water collector configuration that has the highest 

collection efficiency. 

• Section 4 describes the experimental tests that were conducted in the WSU 7- by 

10-ft wind tunnel with the selected water collector configuration. It also describes 

the development and performance of the iso-kinetic flow control (ISFC) system. A 

1-2
discussion on the performance of the probe in terms of the water collection 

efficiencies based on a limited number of experimental data is also provided. 

• Section 5 describes the performance of a modified probe in a laboratory. The highly 

efficient water collector from section 3, which had been tested in a laboratory and a 

wind tunnel, was modified to include a humidity sensor. This section describes the 

relevant humidity equations and discusses the results based on the limited water 

collection efficiency measurement data. 

• Section 6 gives a summary of the work that led to the successful development of the 

reference probe.

• Section 7 provides conclusions on the performance of the probe based on the 

experimental tests conducted. It also provides data on the collection efficiencies and 

standard deviations of the probe with the selected water collector configurations. 

• Section 8 lists recommendations for further work that aim to develop this proof-ofconcept probe into an LWC instrument for Title 14 Code of Federal Regulations 

Part 25, Appendix C and SLD clouds. 

1-3/1-4
2. DESIGN OF AN ISO-KINETIC PROBE.

Figure 2-1 shows a schematic layout of a reference (or iso-kinetic) probe in a wind tunnel that 

was conceived at the beginning of the study. It shows the probe mounted on the tunnel floor and 

connected to a suction pump. The difference in the static pressures from the probe inlet and the 

tunnel wall was fed to a computer system that was programmed to control a flow-metering valve. 

The software was developed to determine the amount of valve movement required to achieve 

iso-kinetic condition at the probe inlet. When this condition was set, the water spray was 

activated for a predefined duration and the water from the droplets entering the probe was 

deposited on a water collector inside the probe. The amount of water collected by the probe 

collector was then used to derive the LWC using the following expression: 

LWC (g/m3) = Mass of water collected per unit time (g/s)

Volume of air drawn by the probe inlet per unit time (m

3

/s) 

ΔP

Suction pump 

Flow metering valve 

(Computer control) 

Iso-kinetic probe 

Wall static pressure 

tapping 

Probe static pressure 

Flow direction tapping 

Tunnel wall 

Computer 

FIGURE 2-1. LAYOUT OF LWC REFERENCE PROBE IN A 

WIND TUNNEL 

Limited information available from published literature [5] showed that a conceptual probe 

design could be based on a total pressure probe with a water collection (or filtration) system and 

suction fan to provide the necessary vacuum pressure. The basic design concept was adopted in 

2-1
the current application for an icing wind tunnel. The anticipated performance of the probe is 

listed below. 

• Capable of measuring LWC of up to 3.0 g/m3. 

• Capable of tunnel velocities of up to 200 mph (limited by the performance of the suction 

fan and probe inlet diameter of 1 inch). 

• Low pressure loss across the water collector system to maximize probe inlet velocity. 

Preliminary tests showed that desiccant materials such as silica gel and molecular sieve were 

able to adsorb water effectively; therefore, the conceptual water collector used these desiccant 

materials to adsorb the incoming water droplets. The tests also identified an industrial suction 

fan that could be used in the design. However, for operations at high tunnel speeds, the pressure 

loss across the probe must be kept to a minimum due to the limited vacuum power of the fan. 

This (low pressure loss) was achieved by having large internal volume to reduce the internal 

flow velocity through the water collector. In addition, lower flow velocities tend to enhance the 

water collection process. These probe design requirements were used to set nominal dimensions 

for the probe and water collector. To minimize fabrication costs, commercially available 

materials such as Perspex and polyethylene were selected for the construction of the probe. 

The following section describes the technical design and fabrication of a conceptual probe. A 

CFD analysis was also conducted to support the design and development of the probe. 

2.1 TECHNICAL DESIGN. 

The design effort was directed mainly on the water collector whose primary function was to 

extract the water from a spray cloud. The conceptual design involved using two coannular (inner 

and outer) cylindrical containers that would be filled with water-adsorbent material. 

After several technical discussions with the WSU machine shop personnel, a technical drawing 

of the conceptual design was produced, as shown in figure 2-2. This figure shows a 90 degree 

elbow tube attached to a solid base with a machined divergent nozzle. The water collector was 

attached to this divergent nozzle end, and the assembly was fitted onto a hollow tube that formed 

the probe’s main body. Figure 2-3 shows the method of sealing the joints between the water 

collector assemblies and the tube. The probe’s main body was attached to a solid base with a 

machined convergent nozzle for connection to a suction fan. The probe is 7 inches in height and 

27 inches in diameter. Figure 2-4 shows a coannular sectional view of the water collector. 

Figures 2-5 to 2-8 show the supporting rings and structures needed to hold wire meshes that 

would form the walls of the coannular containers. The cross-sectional shapes of all the 

components were circular. The fabricated components of the reference probe are described in 

section 2.2. 

2-2
FIGURE 2-2. TECHNICAL DRAWING OF THE REFERENCE PROBE 

FIGURE 2-3. SEALING JOINT DRGW 1 FIGURE 2-4. COANNULAR SECTIONAL 

VIEW OF THE WATER COLLECTOR

2-3
 

FIGURE 2-5. FLANGE 2 FIGURE 2-6. FLANGE 3 

 

FIGURE 2-7. FLANGE 4 FIGURE 2-8. FLANGE 5 

2.2 PROBE FABRICATION.

Most of the components shown in figures 2-2 to 2-8 were fabricated in-house. However, certain 

components such as the suction fan, metering valve, and desiccant materials were bought from 

external suppliers. The probe materials used included Ultra-High-Molecular Weight 

Polyethylene, which has a characteristic white plastic appearance and clear Perspex tube. 

Figure 2-9 shows the various components of the reference probe, and figure 2-10 shows the final 

assembly of the reference probe. A brief description of the various parts follows. 

 

Perspex tube 

Probe base 

section 

Water collector

Probe top 

section 

(inverted) 

 FIGURE 2-9. COMPONENTS OF THE PROBE FIGURE 2-10. PROBE ASSEMBLY 

2-4
The probe top section, figures 2-11 and 2-12, consisted of a 90 degree elbow tube (TNOS-90-

100, Sani-Tech Canada) that was attached to a solid base section with the divergent nozzle 

(figure 2-11). The outer diameter of the tube was 1 inch, the tube thickness was 1/16 inch, and 

the tube dimensions were approximately 5.5 by 5.5 inches. (These tube dimensions were 

different from the technical drawing shown in figure 2-2 because, during the design phase, it was 

not known whether this would be fabricated or purchased from an external company). The 90 

degree elbow tube was detachable from the solid base so that another elbow tube, which had 

been fitted with a total and static pressure ports, as shown in figure 2-13, could be used for inlet 

velocity measurement. The divergent nozzle (of the top section) was 3 inches in diameter at the 

base and extended for about 3 inches to join with the 90 degree elbow tube. The nozzle end was 

machined with an overhang lip (figure 2-12) to prevent surface water (in the probe interior) from 

being blown backward, a phenomenon that can occur when there are strong recirculating flows 

in the water collector chamber. 

 

Divergent 

nozzle

Overhang lip

90 deg elbow 

tube 

Solid body with 

a divergent 

nozzle 

FIGURE 2-11. PROBE INLET—SIDE VIEW FIGURE 2-12. PROBE INLET— 

BOTTOM VIEW 

Total pressure 

probe 

Static pressure 

tapping 

FIGURE 2-13. PROBE WITH TOTAL AND

STATIC PORTS 

2-5
The main body of the probe, shown in figure 2-14, consisted of a single clear Perspex tube that 

was attached to a solid base with a convergent nozzle. The inner diameter of this nozzle was 3 

inches. The outer diameter of the tube was 7 inches, the tube thickness was 5/8 inch, and the 

tube length was approximately 14 inches. Clear Perspex was used because of the need for visual 

examination of the water collector during testing. The probe top section (with the 90 degree 

elbow) was attached to this body and was sealed with an O-ring, as shown in figure 2-3. 

Convergent exit 

nozzle 

FIGURE 2-14. PROBE MAIN BODY AND CONVERGENT OUTLET NOZZLE 

The removable water collection system (figure 2-15) was constructed from two coannular 

cylindrical containers. The diameter and length of the inner container were 3 and 3.5 inches, 

respectively, and the dimensions of the outer container were 5 and 5 inches respectively. This 

gave a void clearance of 1 1/2 inches at the bottom and 1 inch on the side. This (void) would be 

filled either with desiccant materials or hydrophobic fiber. Stainless steel wire mesh with 0.020 

inch in diameter, 0.030 inch opening, and 36% porosity was used to form the sidewalls and base 

of the containers. The bottom wire mesh was removable for the filling of the water-adsorbent 

materials into the void clearance. Figure 2-16 shows the assembled water collector attached to 

the base of the probe top section with four elongated rods. It also shows the external supports for 

the wire mesh, which were machined from Perspex material. 

 

Co-annular 

chamber

Inner container 

Hollow well of 

inner container 

Outer container

FIGURE 2-15. COANNULAR WATER 

COLLECTOR CONTAINER 

FIGURE 2-16. ASSEMBLY OF WATER 

COLLECTION SYSTEM 

2-6
During the operation of the probe, water droplets (from a spray cloud) that entered the probe 

inlet initially splashed and filmed on the 90 degree elbow tube. The inlet flow slowed down 

when it entered the divergent nozzle, which enhanced the process of water filming and runback 

on the internal surfaces. The slow moving air entered the hollow well of the water collector 

before going through the collector filter where the flow velocity was further reduced. This filter 

(or collector) consisted of desiccant materials such as silica gel or molecular sieve that adsorbed 

the water droplets during the transition (passage through the water-adsorbent layer) phase. 

2.3 COMPUTATIONAL FLUID DYNAMICS ANALYSIS.

A CFD study was performed to assess the effect of the large probe main body on the flow 

distribution near the inlet nozzle and to investigate the flow behavior inside the probe. The 

analysis would be used to support the design and development of the probe. It was also hoped 

that the analysis would reveal the aerodynamic features of the probe prior to the experimental 

tests in a laboratory and wind tunnel. The commercially available FLUENT software (version 

5.4) was used for this study. It must be noted that the CFD analysis was carried out during the 

fabrication phase, and the final 90 degree elbow tube dimensions, described in section 2.2, were 

not used in the analysis. As will be shown in section 3, the selected configuration of the water 

collector was also quite different from the current design. 

The following CFD analysis was carried out: 

• Simulation of the probe in the WSU 3- by 4-ft wind tunnel. The smaller tunnel was 

initially selected for experimental tests based on tunnel schedule and cost constraints. 

The final tests, however, were conducted in the larger 7- by 10-ft tunnel because of 

probe installation issues in the smaller tunnel facility. Although the CFD analysis was 

conducted with the smaller tunnel, it was felt that the results will be applicable to the 

larger tunnel facility because the tunnel blockage due to the probe was less than 

10 percent based on the 3- by 4-ft test section. The blockage for the larger tunnel was 

about 2%. 

• Simulation of the water collector. The main objective of this analysis was the flow 

distribution inside the water collector and the passage through the water absorption 

medium. This medium was simulated in FLUENT as a packed bed using an empirically 

specified pressure loss. 

The reason for the separate internal and external flow analyses was to reduce the computer effort 

that would have been required to create a single large computational grid for the internal and 

external probe geometry and the wind tunnel. The coupling of the external flow and internal 

flow analyses was accomplished by using the iso-kinetic flow condition at the inlet of the probe 

for a specified tunnel speed. 

2.3.1 Computational Fluid Dynamics Simulation of the LWC Probe in a Wind Tunnel. 

The WSU 3- by 4-ft facility is an open loop wind tunnel and is powered by a 200-horsepower 

(hp) electric motor that drives a four-bladed, 11-ft-diameter propeller. It can generate flow 

velocities up to 200 mph (90 m/s) in a 3- by 4- by 4-ft-long test section. A computational grid 

2-7
was created to simulate the test section of the wind tunnel. The upstream end of the test section 

was extended by 5 ft, whereas the downstream end was extended by 3 ft. The final dimensions 

of the grid were 3 by 4 by 12 ft. The probe was located in the middle of the wind tunnel floor 

and about 7 ft from the inlet. The extended inlet section ensured a fully developed velocity 

profile at the inlet, while the elongated downstream section ensured complete mixing of any flow 

separation occurring aft of the probe. 

Figure 2-17 shows a three-dimensional computational grid of the test section including the 

reference probe. A total of 800,000 tetrahedral cells were used to create the grid. Figure 2-18 

shows a close-up view of the reference probe. Grid refinement was applied around the probe and 

tunnel walls. The inlet velocity was set to 110 mph (50 m/s) and turbulent intensity was set to 

1%. The inlet velocity profile was assumed to be uniform. The tunnel exit was simulated as a 

pressure boundary and was set to an absolute pressure of 14.46 psi. To simulate iso-kinetic flow, 

the probe inlet nozzle was also simulated as a pressure boundary, but the gauge pressure was set 

to the tunnel exit pressure. The reasons for this were (1) the initial probe inlet pressure was not 

known a priori and (2) the short distance between the probe and tunnel exit, and the assumption 

of smooth wall conditions (hence, low wall frictional losses), implied that their static pressures 

be similar. Therefore, the tunnel wall static pressure, at the location of the probe inlet, can also 

be assumed to be equal to the free-stream static pressure at the test section outlet. 

FIGURE 2-17. COMPUTATIONAL GRID OF THE WIND TUNNEL AND PROBE 

FIGURE 2-18. SOLID MODEL OF THE REFERENCE PROBE 

2-8
The analysis employed the SIMPLE algorithm in the FLUENT software because the pressurevelocity dependency was negligible since the tunnel velocity was quite low. The k-ε RNG 

turbulence model and near-wall functions were also applied to simulate turbulent flow. 

Figures 2-19 and 2-21 show the predicted streamlines and velocity vectors around the reference 

probe (velocity magnitudes are indicated by the color distributions). The streamlines in 

figure 2-19 indicate a small upturn in flow direction near the edge of the top section (of the 

probe) where the free stream approaches the probe. However, this small upturn flow has no 

significant effect on the free stream near the probe inlet. Close-up views of the flow field in 

figures 2-20 and 2-21 indicate that the streamlines entering the probe inlet were parallel, 

demonstrating that the flow at the probe inlet was iso-kinetic flow (i.e., same velocity as the free 

stream). The separated flow regions aft of the main body of the probe and the 90 degree elbow 

tube, shown in figure 2-21, were also quite small and had no significant effect on the probe inlet 

flow. 

FIGURE 2-19. PREDICTED STREAMLINES—SIDE VIEW 

 

FIGURE 2-20. PREDICTED VELOCITY 

VECTORS AND STREAMLINES— 

ISOMETRIC VIEW 

FIGURE 2-21. PREDICTED VELOCITY 

VECTORS AND STREAMLINES— 

TOP VIEW 

2-9
2.3.2 Computational Fluid Dynamics Simulation of the Water Collector. 

The technical design, shown in figure 2-2, was used to create a computational grid of the 

reference probe shown in figure 2-22. The coannular water collector was modeled as two thin 

cylindrical shells. The inner container (or shell) has a hollow well (3 inches in diameter) that 

was attached to the divergent nozzle of the probe top section. Figure 2-22 shows the 

computational grid of the probe including the water collector. A total of 100,000 tetrahedral 

cells were used to model the probe geometry. No grid refinement was used because it was not 

possible to define the pressure drop across the porous medium with any degree of accuracy due 

to the lack of experimental data. Therefore, only approximate flow distributions inside the probe 

could be expected from the predicted results. 

Probe inlet

Probe outlet

Water 

collector 

FIGURE 2-22. COMPUTATIONAL GRID OF THE REFERENCE PROBE 

Pressure boundary conditions were applied at the probe inlet and outlet ports of the probe. The 

total pressure at the probe inlet was fixed to ambient total pressure. The probe inlet velocity was 

computed from the CFD analysis. The gauge pressure at the probe outlet was set to an absolute 

pressure of 14.55 psi to simulate suction. The pressure boundary condition at the probe outlet 

was intended to simulate realistic suction pressure that would have been provided by a suction 

fan. 

The collector, simulated as a packed bed, consisted of silica gel pellets. Molecular sieve 

desiccants were not modeled due to time and cost constraints. The FLUENT software employs 

Ergun’s correlation to simulate flows through a porous medium. The semiempirical correlation 

is applicable for a range of Reynolds numbers and types of packed beds, and is written as 

follows: 

3

2

32

2

)1(150 )1(75.1

ε

ερ

ε

νεμ ν

DL p Dp

p − + − = ∇ (2-1) 

2-10
where 

∇p = pressure drop across porous medium (Pa) 

ρ = air density (kg/m3) 

μ = air viscosity (kg/ms) 

ε = void fraction 

Dp = mean particle diameter (m) 

 ν = superficial velocity flowing through the medium (m/s) 

 L = thickness of the porous medium (m) 

The FLUENT software requires the above terms to be entered as the pressure loss coefficients, α

and β, which are written as follows: 

β ρ

α

μν

2

2

v

L

p +=∇ (2-2) 

When the flow through the porous medium is turbulent, which was assumed in the present 

analysis, the first term in equation 2-1 is usually zero. (For laminar flow, the second term tends 

to zero.) Therefore, ignoring the first term and comparing equation 2-2 with 2-1 gives 

3

)1(5.3

ε

ε β Dp− = (2-3) 

The mean diameter of silica gel was 0.050 inch (1.27e-3m). The void fraction (in equation 2-3) 

was estimated since no data could be found in published literature. Through a process of trial 

and error, the void fraction value of 0.4 (β ~26,000) was found to provide a probe inlet velocity 

of approximately 110 mph (50m/s). Higher velocity range was not investigated due to time and 

cost constraints. The probe inlet turbulent intensity was set to 1%, which was similar to the 

value previously set for the wind tunnel computations. The analysis employed the SIMPLE 

algorithm in FLUENT, together with the k-ε RNG turbulence model and near-wall functions. 

The predicted results are shown in figures 2-23 to 2-28. 

Figure 2-23 shows that the flow velocity remained fairly constant along the 90 degree elbow tube 

until it reached the divergent section where a nonuniform decelerating flow was found. The core 

flow depicted in figure 2-24 is biased towards one side of the divergent section and the hollow 

well of the inner container. The inlet velocity of 110 mph (50 m/s) was reduced to about 4 mph 

(2 m/s) inside the hollow well. To assess the pressure distribution inside the collector, a contour 

plane was created at about 2.3 inches from the top edge of the water collector, as shown in 

figure 2-27. Contour plots of the Y-velocity component and static pressure distributions are 

shown in figures 2-25 and 2-26, respectively. These figures show two distinct flow patterns, 

which suggest that a recirculating flow has developed inside the inner container. Figures 2-27 

and 2-28 show the flow streamlines through the water collector (or porous medium). These 

streamlines indicate that the flow was uniformly distributed around the collector. 

2-11
FIGURE 2-23. PREDICTED VELOCITY 

VECTORS INSIDE THE PROBE 

FIGURE 2-24. STREAMLINES DISTRIBUTION 

INSIDE THE PROBE 

FIGURE 2-25. VELOCITY CONTOUR 

ACROSS COLLECTOR—TOP VIEW 

FIGURE 2-26. PRESSURE DISTRIBUTION 

ACROSS COLLECTOR—TOP VIEW 

Water collector 

Low pressure 

region 

Probe inlet 

High pressure 

region 

Water collector 

Probe inlet 

Flows going

into page 

Flows going 

out of page 

2-12
Contour plane at

2.3 inches from

top surface

FIGURE 2-27. STREAMLINES 

DISTRIBUTION INSIDE PROBE— 

PROBE MAIN BODY REMOVED 

FIGURE 2-28. STREAMLINES 

DISTRIBUTION INSIDE PROBE— 

TOP VIEW 

In summary, the CFD analysis performed indicate the following trends: 

• The large probe main body has negligible effects on the iso-kinetic flow at the probe 

inlet. 

• The flow separation aft of the probe was quite small; therefore, the effects on the isokinetic flow were also negligible. 

• The flows inside the probe were biased towards one side of the divergent nozzle that 

continued into the inner container. 

• A recirculating flow might have developed inside the hollow well of the inner container. 

• The flow distribution through the porous medium had exhibited an even distribution 

around the outer container. However, this (effect) may be due to the boundary conditions 

that were used to simulate the porous medium. 

2-13/2-14
3. EXPERIMENTAL INVESTIGATION IN A LABORATORY.

This section describes the experimental tests with the reference probe that was conducted in the 

laboratory. It also describes the experimental setup, characteristics of the water-adsorbent 

materials used, and the different methods of water collection employed during the investigation. 

The basic test methodology was to weigh the water collector that contained the adsorbent 

materials (and adsorbed water) and compare this to the amount of water injected directly into the 

probe. The main experimental effort involved the selection of a water collector configuration 

capable of high collection efficiencies over a range of LWC intensities. The selected collector 

configuration was subjected to an extended test program to define its collection efficiency. The 

equipment used in the tests included the reference probe, suction fan, U-tube water manometer, 

and an air-spray brush. 

3.1 EXPERIMENTAL SETUP.

Figure 3-1 shows the basic experimental setup, which was designed to conduct water collection 

efficiency tests on the reference probe. Figure 3-2 shows a similar schematic layout of the 

reference probe, suction fan and a U-tube water manometer. Figure 3-1 shows the reference 

probe attached to a wooden base, which was used to raise the probe above the floor so that the 

flexible hose connecting the probe outlet to the suction fan could be attached to the probe. The 

90 degree elbow tube of the probe was equipped with four static pressure ports; however, only 

one port was connected to the single-channel water manometer during the early tests because the 

pressure differences between the four ports was minimal. No flow control was used to set isokinetic conditions at the inlet since the initial effort was directed at selecting an efficient method 

of water collection. 

 

Suction fan 

Reference probe 

Probe static 

pressure tapping 

U-tube manometer 

U-tube manometer 

Suction fan 

Probe static 

pressure port 

Reference 

probe 

 FIGURE 3-1. EXPERIMENTAL SETUP FIGURE 3-2. SCHEMATIC SETUP 

3-1
A description of the main components of the experimental setup (figure 3-1) is given below. 

• Suction Fan—The suction fan was part of a standard 6.5-hp industrial wet and dry 

vacuum system (RIDGID WD#1735, Emerson Tool Company). The vacuum system 

consisted of a storage base tank, two extension wands, two 6-ft flexible hoses, and 

several hose couplings. The suction fan had an inlet and an outlet port, and was normally 

attached to the base tank. However, this (tank) was removed to optimize the vacuum 

produced by the fan. The aerodynamic performance of the fan was determined by slowly 

increasing the flow resistance at the inlet port (blocking with increasing number of 

porous layers) while the outlet port was opened to the atmospheric conditions. By taking 

the ratio of the static pressures of the inlet (P1) and outlet ports (P2) over a range of 

volumetric flows, the pressure ratios (P2/P1) as a function of volumetric flow rate were 

obtained, as shown in figure 3-3. 

0.04 0.06 0.08 0.1

Volume flow rate (m3/s)

1

1.02

1.04

1.06

1.08

1.1

Pressure ratio (P2/P1)

Suction fan port diameters

Inlet dia. = 3.5 inch

Outlet dia. = 2.0 inch

curve-fit

FIGURE 3-3. AERODYNAMIC PERFORMANCE OF SUCTION FAN 

• Spray Brush—An air-spray brush (Paasche double action airbrush, #VL-SET, Passche 

Airbrush Company) was used to generate water droplets in the form of a spray cloud. 

The brush (figure 3-4) was approximately 6 inches long by 5/8 inches in diameter 

(measured at 3 inches from exit nozzle). Water from a small glass bottle was drawn into 

the brush nozzle via a vacuum created by a high-pressure air supply that was connected 

near the brush exit nozzle. The cloud plume size and penetration length depended on the 

spray pressure and a lever that controlled the water flow rate, e.g., at 30 psig and midlevel 

lever setting, the plume size was approximately 12 inches long and 3 inches in diameter 

(measured at about 6 inches from the spray nozzle exit). The droplet sizes produced by 

the spray brush were not measured (due to time and cost constraints), but it was estimated 

that at a spray pressure of 30 psig, the droplet size generated was approximately 20 to 30 

microns. During experimental tests, the spray brush was placed at about 1 1/2 inches 

from the reference probe’s inlet, as shown in figure 3-4. This ensured that all water 

droplets from the spray plume would enter the probe. 

3-2
Spray brush 

Probe inlet

FIGURE 3-4. DIRECT METHOD OF WATER INJECTION WITH THE 

SPRAY BRUSH 

• Water Collector System—The basic water collector was fabricated from two coannular 

containers with wire-meshed walls, as shown in figure 3-5. The water collector was 

attached to the divergent nozzle of the probe top section by four elongated screws. 

Figure 3-6 shows the various components of the water collector and their association to 

the inner and outer container. 

Outer container 

with wire-mesh 

sidewalls 

Supports for 

outer container 

Inner container with 

wire-mesh sidewalls 

Bottom 

wall of 

outer 

container

Probe top section 

Water collector 

FIGURE 3-5. WATER COLLECTOR 

ASSEMBLY 

FIGURE 3-6. VARIOUS COMPONENTS OF 

THE COLLECTOR 

The void between the inner and outer container was filled with either silica gel or molecular 

sieve pellets mixed with polystyrene foam cuttings (figure 3-7). The filling process involved 

turning the collector upside down and then removing the wire mesh that formed the bottom wall 

of the outer container (figure 3-6). The addition of polystyrene cuttings helped to increase the 

porosity of the filling and disperse the desiccant pellets in the large void space. The collector 

was initially designed for silica and molecular sieve pellets but it was later modified to include 

other materials such as water-adsorbent paper, B-Gon fiber mesh, and blotter paper. The paper 

and B-Gon fiber mesh were wrapped around the inner container, as shown in figures 3-8 and 3-9, 

respectively. Blotter paper was rolled into a tube and installed at the exit end of the diverging 

nozzle, as shown in figure 3-10. 

3-3
Polystyrene foam 

cuttings 

Silica gel 

Outer 

container 

Molecular 

sieve

Inner container wrapped with 

adsorbent paper 

Disk-shaped paper to 

cover base of container 

FIGURE 3-7. METHOD OF INSTALLING 

SILICA GEL AND MOLECULAR SIEVE 

FIGURE 3-8. WATER-ADSORBENT PAPER 

WRAPPED AROUND INNER CONTAINER 

Disk-shaped B-Gon to 

cover base of container

Inner container 

wrapped with B-Gon

Cylindrical blotter paper 

tube (installed) 

FIGURE 3-9. B-GON WRAPPED AROUND 

INNER CONTAINER OF COLLECTOR 

FIGURE 3-10. BLOTTER PAPER 

ATTACHED TO THE DIVERGENT NOZZLE 

3.2 WATER-ADSORBENT MATERIALS. 

The types of water-adsorbent materials that were tested included the following: 

• Silica gel desiccant (figure 3-11)—Silica gel is silicon dioxide (SiO2), which is a 

naturally occurring mineral that has been purified and processed into either granular or 

beaded form. It has an average pore size of 24 angstroms and has a strong affinity for 

moisture. The silica gel will adsorb moisture at temperatures up to 220°F (105°C). Silica 

gel performs best at room temperatures (70° to 90°F) and high humidity (60% to 90% 

relative humidity (RH)). Silica gel has a characteristic white crystalline structure, and the 

sizes of the beads are normally between 0.020 and 0.079 inch (0.5 and 2 mm). 

• Molecular sieve desiccant (figure 3-12)—Molecular sieve is a porous crystalline 

aluminosilicate, a synthetic desiccant that has a very strong affinity for moisture. The 

distinctive feature of the molecular sieve structure, compared to other desiccants, is the 

uniformity of the pore size openings in the crystal lattice structure. Based on the product 

literature, the most commonly used pore size is 4 angstroms (4A), although pore sizes of 

3 angstroms (3A), 5 angstroms (5A), and 10 angstroms (13X) are also available. A small 

pore size allows the selection of a molecular sieve product that can adsorb water, yet 

3-4
exclude most other molecules, such as volatile organics. Molecular sieve desiccants have 

a characteristic brown-colored, spherical-shaped pellet with sizes that are normally 

between 0.028 and 0.039 inch (0.7 and 1.0 mm). 

• DRIMOP desiccant (figure 3-13)—DRIMOP is a super liquid absorber that can adsorb 

water or other fluids up to 300 times its own weight. In the presence of any fluid (based 

on product literature), a DRIMOP packet quickly bursts open, releasing a superadsorbent 

polymer powder, which quickly absorbs and immobilizes the fluid. DRIMOP type 

desiccants have a characteristic white powdery substance. 

• B-Gon fiber mesh (figure 3-14)—B-Gon filaments are normally aligned perpendicular to 

the airflow for maximum droplet removal efficiency. B-Gon filament has a unique 

interlacing knitted structure oriented into a ladder arrangement, hence, it can cause a 

change in direction of vapor flow. This effect enhances droplet removal by impaction, 

interception, and centrifugal actions. The material removes water droplets by trapping 

them between the interlaced mesh, which is hydrophobic. 

• Domestic paper (figure 3-15)—These are industrial strength domestic water-adsorbent 

papers that are readily available from most grocery stores. 

• Blotter paper (figure 3-16)—This type of paper (Verigood #100 Blotter paper) was used 

in the water impingement tests with the dye tracer technique, which had been reported by 

Papadakis, et al. [6]. 

 

Molecular 

Silica gel sieve 

FIGURE 3-11. SILICA GEL FIGURE 3-12. MOLECULAR SIEVE 

DRIMOP 

FIGURE 3-13. DRIMOP FIGURE 3-14. B-GON FIBER MESH 

3-5
Blotter paper 

Blotter paper rolled 

into a cylindrical tube 

FIGURE 3-15. WATER-ADSORBENT PAPER FIGURE 3-16. BLOTTER PAPER 

The amount of adsorbent materials required for a test depends on the material type and amount 

of water to be injected into the probe. In the case of silica gel or molecular sieve, the amount 

required also depends on the RH and temperature of the test condition. For example, at a RH of 

50% and 77°F, silica gel adsorbs approximately 25% of its own weight, but at 100°F, it can only 

adsorb about 15% of its own weight. The desiccant’s water absorption capacity with respect to 

the RH and temperature are shown in appendix A, figures A-1 and A-2 respectively. In the case 

of the adsorbent paper, blotter paper, and B-Gon fiber mesh, no data could be found; therefore, 

the degree of water penetration is the only method of assessment. B-Gon fiber is hydrophobic, 

hence, it does not adsorb water, instead, water droplets are trapped between the fiber layers. 

Therefore, collection efficiency is dependent on the number of layers used. 

3.3 PRELIMINARY TESTS. 

The objective of the preliminary tests was to define and select an efficient method of water 

collection. The basic test methodology was to inject a known amount of water (stored in a glass 

container) directly into the probe and then compare this to the amount caught by the water 

collector. A spray nozzle was used to deliver a measured amount of water in the form of a cloud 

consisting of a range of droplet sizes. These tests were conducted in the WSU laboratory. Test 

procedures were established (based on preliminary tests) for conducting this kind of gravimetric 

measurements. This involved weight measurements of the silica gel and molecular sieve pellets 

together with polystyrene cuttings (figure 3-7). These efforts led to the development of the 

following test procedure: 

• Place collector in a plastic bag to minimize evaporation, weigh, and record data (mg). 

• Weigh and record water bottle of the spray brush (mg). 

• Set spray brush volume control lever and record supply air pressure (psig). 

• Clear out any remaining water in the spray brush with compressed air. Then using 

another water bottle, refill the spray brush and connecting tube with water, ensuring there 

are no visible air bubbles in the tube. 

3-6
• Replace the water bottle with the one to be used for testing, taking care to ensure that no 

water was lost during the transfer. 

• Set the distance between the probe inlet and spray brush to approximately 1.5 inches 

using a specially designed fixture. 

• Start suction fan and allow airflow to settle for at least 3 seconds. 

• Start water spray and record start time. 

• Spray for a fixed time period. 

• Remove water collector and place inside a plastic bag to prevent evaporation. Weigh and 

record (mg). 

• Weigh and record remaining water in the glass container (mg). Again, ensure the full 

length of the nozzle plastic tube is filled with water and there are no visible air bubbles. 

• Compute the collection efficiency using the following equation: 

 Collection efficiency (%) = Mass of water collected by probe per unit time (g/s) x 100 

 Mass of water injected locally into the probe per unit time (g/s) 

 Water spray rate (g/s) = Mass of water injected locally into the probe (g)

 Spray duration (s) 

A number of water collection efficiency tests were also conducted during the process of defining 

the above test procedure. However, the probe collection efficiencies were quite low and the data 

was scattered due to the following: 

• The resolution of the electronic balance used in the tests did not have sufficient accuracy 

for performing gravimetric measurements. The balance had a load capacity of 1 kg and 

resolution of 0.1 g. Although higher resolution balances such the Denver Instrument 

P-214 and Mettler Toledo AG204 (load capacity 210 mg, resolution 0.1 mg) were 

available, they were not used because the dry weight of the water collector alone 

(586 mg) was greater than the maximum load capacity of these balances. 

• The desiccant pellets that were trapped in the wire mesh at the end of a test could not be 

easily removed, therefore, subsequent tests often included the weight of the trapped 

pellets. 

• Some desiccants might have been lost through the wire-meshed walls of the water 

collector. The sizes of molecular sieve pellets ranged from 0.028 to 0.039 inch (silica gel 

sizes varied from 0.020 to 0.079 inch), whereas the size of the wire opening was 

0.030 inch. 

3-7
• The process of having to replace wetted polystyrene cuttings with dried materials after a 

test was time-consuming and tedious. This effort was necessary to minimize the 

measurement errors caused by the remaining surface water in the polystyrene foam. 

In conclusion, it was difficult to ascertain the probe collection efficiency with the current 

conceptual design that relied solely on desiccant materials; therefore, it was decided to seek an 

alternative method of capturing the water mass. 

3.4 WATER COLLECTOR CONFIGURATION TESTS. 

As a result of the problems experienced with the conceptual water collector design, a number of 

different methods of configuring the water collector were conceived and tested. These methods 

used a higher-resolution electronic balance (load capacity 210 mg, resolution 0.1 mg) by 

discarding the wire mesh from the water collector. The previous objectives were adopted: to 

define and select an efficient method of water collection. 

A total of 11 different water collector configurations were investigated with the test procedures 

defined in section 3.3. Some configurations involved minor modifications to the collector while 

others required considerable modifications. Descriptions of the various collectors tested and 

related test findings are given in appendix B. The tabulated results are shown in tables 3-1 to 

3-12. The following water-adsorbent materials were tested: 

• Silica gel desiccant 

• Molecular sieve desiccant 

• DRIMOP liquid adsorber 

• Water-adsorbent paper 

• Blotter paper 

• B-Gon fiber mesh 

The findings presented in appendix B indicate that configuration 11 Mod-I had the highest water 

collection efficiency, which was approximately 100%. The configuration 11 Mod-I design used 

a plastic container with a straight exit tube, a circular B-Gon pouch filled with silica gel 

desiccant and a cylindrical blotter paper tube (figures B-11a and B-11b, appendix B). The 

maximum probe inlet static pressures recorded in the tests were approximately 0.94 psig 

(26′′H2O). In summary, this design was selected for further experimental tests to better define its 

measurement accuracy and resolution. 

3-8
3-9

TABLE 3-1. TEST RESULTS FOR CONFIGURATION 1 

Weight of 

B-Gon and 

Inner Container 

Weight of 

Spray Water Used Test 

No. Before After 

Amount 

of Water 

Collected

(g) Before After 

Amount 

of Water 

Used 

(g) 

Spray 

Pressure 

(psig) 

Spray 

Duration

(s) 

Run 

Duration

(s) 

Rate 

of 

Spray

(g/s) 

Collection Efficiency

(%) 

Water 

Lost/Gain

(g) 

1 80.0947 85.0182 4.9235 95.2665 87.3204 7.9461 20.0 15.0 45.0 0.530 62.0 (3.0226)2 81.3960 91.8323 10.4363 94.2515 80.2109 14.0406 20.0 20.0 40.0 0.702 74.3 (3.6043)3 81.6971 88.5511 6.8540 97.3618 87.4796 9.8822 20.0 20.0 40.0 0.494 69.4 (3.0282)4 81.1567 91.2813 10.1246 93.5384 79.0897 14.4487 20.0 30.0 50.0 0.482 70.1 (4.3241)5 78.9429 81.9474 3.0045 93.3290 87.2922 6.0368 30.0 40.0 40.0 0.151 49.8 (3.0323)6 79.2922 82.2144 2.9222 98.8672 92.8455 6.0217 30.0 40.0 40.0 0.151 48.5 (3.0995)7 78.9537 81.1839 2.2302 90.3139 85.8489 4.4650 30.0 30.0 30.0 0.149 49.9 (2.2348)8 79.1789 81.2924 2.1135 91.0674 86.6082 4.4592 30.0 30.0 30.0 0.149 47.4 (2.3457)9 79.0789 80.3859 1.3070 92.7830 89.9203 2.8627 30.0 20.0 20.0 0.143 45.7 (1.5557)

10 79.4126 81.2306 1.8180 95.0960 91.1005 3.9955 30.0 30.0 30.0 0.133 45.5 (2.1775)11 79.2058 80.8335 1.6277 91.8306 86.3616 5.4690 30.0 60.0 60.0 0.091 29.8 (3.8413)12 78.9968 80.1795 1.1827 92.9018 88.8964 4.0054 30.0 45.0 45.0 0.089 29.5 (2.8227)13 79.2070 80.6418 1.4348 92.8970 87.7963 5.1007 30.0 60.0 60.0 0.085 28.1 (3.6659)14 78.8421 79.9259 1.0838 93.4174 89.4899 3.9275 30.0 45.0 45.0 0.087 27.6 (2.8437)15 78.8747 79.6471 0.7724 93.3208 90.7845 2.5363 30.0 30.0 30.0 0.085 30.5 (1.7639)16 79.0391 79.6475 0.6084 95.4638 92.9663 2.4975 30.0 30.0 30.0 0.083 24.4 (1.8891)
3-10

TABLE 3-2. TEST RESULTS FOR CONFIGURATION 2 

Weight of 

Adsorbent Paper and 

Inner Container 

Weight of 

Spray Water Used Test 

No. Before After 

Amount 

of Water 

Collected

(g) Before After 

Amount 

of Water 

Used 

(g) 

Spray 

Pressure

(psig) 

Spray 

Duration

(s) 

Rate of 

Spray

(g/s) 

Collection 

Efficiency 

(%) 

Water 

Lost/Gain

(g) 

1 73.3305 76.0834 2.7529 90.8320 85.5910 5.2410 30.0 30.0 0.175 52.5 (2.4881)2 72.3537 75.0586 2.7049 90.4083 85.1937 5.2146 30.0 30.0 0.174 51.9 (2.5097)3 73.3763 76.6164 3.2401 92.9054 86.7185 6.1869 30.0 40.0 0.155 52.4 (2.9468)4 73.7878 76.0171 2.2293 92.6764 88.0524 4.6240 30.0 30.0 0.154 48.2 (2.3947)5 73.5581 74.9976 1.4395 94.0638 91.0642 2.9996 30.0 20.0 0.150 48.0 (1.5601)6 73.6162 75.6668 2.0506 95.4575 91.0520 4.4055 30.0 30.0 0.147 46.5 (2.3549)7 73.8104 75.1116 1.3012 92.2182 89.2717 2.9465 30.0 20.0 0.147 44.2 (1.6453)8 73.3724 74.2440 0.8716 89.0420 86.8317 2.2103 30.0 20.0 0.111 39.4 (1.3387)9 73.1410 74.6429 1.5019 92.5413 87.1217 5.4196 30.0 60.0 0.090 27.7 (3.9177)

10 72.4733 73.9074 1.4341 93.8633 88.4915 5.3718 30.0 60.0 0.090 26.7 (3.9377)11 72.9550 73.9924 1.0374 93.6235 89.6990 3.9245 30.0 45.0 0.087 26.4 (2.8871)12 73.2227 73.9091 0.6864 88.4445 85.8528 2.5917 30.0 30.0 0.086 26.5 (1.9053)13 72.9897 73.6444 0.6547 94.5960 92.0730 2.5230 30.0 30.0 0.084 25.9 (1.8683)14 72.2985 73.2107 0.9122 92.0232 88.2262 3.7970 30.0 45.0 0.084 24.0 (2.8848)15 78.8421 80.3202 1.4781 92.4853 87.2714 5.2139 30.0 60.0 0.087 28.3 (3.7358)16 77.6879 78.4457 0.7578 95.0779 92.5265 2.5514 30.0 30.0 0.085 29.7 (1.7936)
3-11

TABLE 3-3. TEST RESULTS FOR CONFIGURATION 3 

Weight of 

Adsorbent Paper and 

Inner Container 

Weight of 

Spray Water Used Test 

No. Before After 

Amount of 

Water 

Collected 

(g) Before After 

Amount 

of Water 

Used 

(g) 

Spray 

Pressure

(psig) 

Spray 

Duration

(s) 

Rate of 

Spray 

(g/s) 

Collection Efficiency

(%) 

Water 

Lost/Gain

(g) 

1 72.6993 74.6695 1.9702 84.2895 81.1602 3.1293 30.0 20.0 0.156 63.0 (1.1591) 2 73.2607 76.3671 3.1064 86.7599 81.7507 5.0092 30.0 40.0 0.125 62.0 (1.9028) 3 73.4383 76.5352 3.0969 88.5750 83.6392 4.9358 30.0 40.0 0.123 62.7 (1.8389) 4 73.3785 74.8550 1.4765 86.8056 84.3507 2.4549 30.0 20.0 0.123 60.1 (0.9784) 5 73.2213 74.9275 1.7062 87.6242 84.5531 3.0711 30.0 30.0 0.102 55.6 (1.3649) 6 73.0702 74.8106 1.7404 88.1487 85.1508 2.9979 30.0 30.0 0.100 58.1 (1.2575) 7 72.9659 73.4394 0.4735 82.7816 81.6168 1.1648 30.0 30.0 0.039 40.7 (0.6913) 

TABLE 3-4. TEST RESULTS FOR CONFIGURATION 4 

Weight of Adsorbent 

Paper, Inner Container, 

and External Layer 

Weight of 

Spray Water Used Test 

No. Before After 

Amount of 

Water 

Collected

(g) Before After 

Amount 

of Water 

Used 

(g) 

Spray 

Pressure

(psig) 

Spray 

Duration

(s) 

Rate of 

Spray 

(g/s) 

Collection 

Efficiency

(%) 

Water 

Lost/Gain

(g) 

1 78.7019 80.0280 1.5026 86.9154 84.1593 2.7561 30.0 30.0 0.092 54.5 (1.2535) 

8.8295 9.0060 0.1765 

2 72.2771 72.4005 1.3282 87.7268 85.0075 2.7193 30.0 30.0 0.091 48.8 (1.3911) 

8.6252 8.6566 0.0314 

17.3701 18.5435 1.1734 
3-12

TABLE 3-5. TEST RESULTS FOR CONFIGURATION 5 

Weight of 

B-Gon Fiber 

Weight of 

Spray Water Used Test 

No. Before After 

Amount of 

Water 

Collected

(g) Before After 

Amount 

of Water 

Used 

(g) 

Spray 

Pressure 

(psig) 

Spray 

Duration

(s) 

Rate of 

Spray

(g/s) 

Collection Efficiency 

(%) 

Water 

Lost/Gain

(g) 

1 85.2527 86.7602 1.5075 85.1426 82.3332 2.8094 30.0 30.0 0.094 53.7 (1.3019) 2 74.8078 75.3882 0.5804 87.4788 84.7010 2.7778 30.0 30.0 0.093 20.9 (2.1974) 3 78.4893 79.6624 1.1731 79.8775 76.1733 3.7042 30.0 40.0 0.093 31.7 (2.5311) 4 72.7063 73.7122 1.0059 82.4832 78.7968 3.6864 30.0 40.0 0.092 27.3 (2.6805) 5 87.6121 89.6425 2.0304 90.5121 85.1727 5.3394 30.0 60.0 0.089 38.0 (3.3090) 6 86.5964 88.7319 2.1355 89.1114 83.7457 5.3657 30.0 60.0 0.089 39.8 (3.2302) 7 78.0692 80.1724 2.1032 85.7223 82.2259 3.4964 30.0 40.0 0.087 60.2 (1.3932) 8 78.4445 80.1853 1.7408 86.2377 82.8072 3.4305 30.0 40.0 0.086 50.7 (1.6897) 9 78.2206 79.6005 1.3799 86.7059 84.1339 2.5720 30.0 30.0 0.086 53.7 (1.1921) 

10 72.3130 75.1992 2.8862 86.0644 80.9438 5.1206 30.0 60.0 0.085 56.4 (2.2344) 11 72.7655 74.8718 2.1063 80.1412 76.7232 3.4180 30.0 40.0 0.085 61.6 (1.3117) 12 99.5902 100.9363 1.3461 90.2754 87.7521 2.5233 30.0 30.0 0.084 53.3 (1.1772) 13 72.9355 73.9991 1.0636 82.7389 80.1412 2.5977 30.0 40.0 0.065 40.9 (1.5341) 14 72.3013 73.3302 1.0289 88.1174 86.2886 1.8288 30.0 30.0 0.061 56.3 (0.7999) 
3-13

TABLE 3-6. TEST RESULTS FOR CONFIGURATION 6 

Weight of Adsorbent 

Material and 

Plastic Container 

Weight of 

Spray Water Used Test 

No. Before After 

Amount of 

Water 

Collected

(g) Before After 

Amount 

of Water 

Used 

(g) 

Spray 

Pressure 

(psig) 

Spray 

Duration

(s) 

Rate of 

Spray 

(g/s) 

Collection 

Efficiency 

(%) 

Water 

Lost/Gain

(g) 

1 99.0056 100.7548 1.7492 88.5719 85.3426 3.2293 30.0 30.0 0.108 54.2 (1.4801) 2 104.5306 106.5054 1.9748 92.1606 89.1310 3.0296 30.0 30.0 0.101 65.2 (1.0548) 3 102.7610 104.6033 1.8423 94.9042 92.1925 2.7117 30.0 30.0 0.090 67.9 (0.8694) 4 124.3563 125.6231 1.2668 90.7507 88.5982 2.1525 30.0 30.0 0.072 58.9 (0.8857) 

TABLE 3-7. TEST RESULTS FOR CONFIGURATION 7 

Weight of Adsorbent 

Paper and 

Inner Container 

Weight of 

Spray Water Used Test 

No. Before After 

Amount 

of Water 

Collected

(g) Before After 

Amount 

of Water 

Used 

(g) 

Spray 

Pressure 

(psig) 

Spray 

Duration

(s) 

Rate of 

Spray 

(g/s) 

Collection Efficiency

(%) 

Water 

Lost/Gain

(g) 

1 72.7848 73.4981 1.8635 83.6655 80.6981 2.9674 30.0 30.0 0.099 62.8 (1.1039) 

27.5824 28.7326 1.1502 

2 73.7672 74.6169 1.7944 86.4554 83.6698 2.7856 30.0 30.0 0.093 64.4 (0.9912) 

29.5675 30.5122 0.9447 

3 72.5520 72.8521 1.5631 80.7365 77.9319 2.8046 30.0 30.0 0.093 55.7 (1.2415) 

21.4213 22.6843 1.2630 

4 78.2328 78.3774 1.3855 85.1927 82.4825 2.7102 30.0 30.0 0.090 51.1 (1.3247) 

21.3306 22.5715 1.2409 

5 72.9413 72.9870 0.4935 82.9388 80.7454 2.1934 30.0 30.0 0.073 22.5 (1.6999) 

21.4078 21.8556 0.4478 
3-14

TABLE 3-8. TEST RESULTS FOR CONFIGURATION 8 

Weight of 

Adsorbent Paper and 

Inner Container 

Weight of 

Spray Water Used Test 

No. Before After 

Amount of 

Water 

Collected 

(g) Before After 

Amount 

of Water 

Used 

(g) 

Spray 

Pressure

(psig) 

Spray 

Duration

(s) 

Rate of 

Spray

(g/s) 

Collection Efficiency

(%) 

Water 

Lost/Gain

(g) 

1 93.0045 94.8051 1.8006 89.3605 85.7555 3.6050 30.0 30.0 0.120 49.9 (1.8044) 2 79.0591 80.7054 1.6463 86.3550 83.6713 2.6837 30.0 30.0 0.089 61.3 (1.0374) 3 86.2514 88.0427 1.7913 83.6609 81.0265 2.6344 30.0 30.0 0.088 68.0 (0.8431) 4 91.9878 93.3791 1.3913 85.7491 83.1269 2.6222 30.0 30.0 0.087 53.1 (1.2309) 
3-15

TABLE 3-9. TEST RESULTS FOR CONFIGURATION 9 

Weight of 

Adsorbent Paper and 

Inner Container 

Weight of 

Spray Water Used Test 

No. Before After 

Amount of 

Water 

Collected

(g) Before After 

Amount 

of Water 

Used 

(g) 

Spray 

Pressure 

(psig) 

Spray 

Duration 

(s) 

Rate of 

Spray 

(g/s) 

Collection 

Efficiency

(%) 

Water 

Lost/Gain

(g) 

1 95.9549 97.9392 1.9843 152.1853 149.4555 2.7298 30.0 30.0 0.091 72.7 (0.7455) 2 95.9874 97.7410 1.7536 156.0295 153.5257 2.5038 30.0 30.0 0.083 70.0 (0.7502) 3 97.9875 99.4920 1.5045 148.7345 146.3160 2.4185 30.0 30.0 0.081 62.2 (0.9140) 4 95.7001 97.4659 1.7658 150.6670 148.2512 2.4158 30.0 30.0 0.081 73.1 (0.6500) 5 98.3654 100.1135 1.7481 158.3974 155.9930 2.4044 30.0 30.0 0.080 72.7 (0.6563) 6 96.8822 98.5971 1.7149 151.8985 149.5498 2.3487 30.0 30.0 0.078 73.0 (0.6338) 7 97.9982 99.5223 1.5241 154.9552 152.6982 2.2570 30.0 30.0 0.075 67.5 (0.7329) 8 96.5970 98.1719 1.5749 153.4981 151.2565 2.2416 30.0 30.0 0.075 70.3 (0.6667) 9 95.9860 97.4319 1.4459 151.5290 149.3179 2.2111 30.0 30.0 0.074 65.4 (0.7652) 

10 95.2894 96.8729 1.5835 158.1864 156.0017 2.1847 30.0 30.0 0.073 72.5 (0.6012) 11 96.0744 97.6534 1.5790 151.2011 149.0385 2.1626 30.0 30.0 0.072 73.0 (0.5836) 12 95.8827 97.4501 1.5674 147.2483 145.1044 2.1439 30.0 30.0 0.071 73.1 (0.5765) 13 95.6692 97.1475 1.4783 154.1017 152.0109 2.0908 30.0 30.0 0.070 70.7 (0.6125) 14 95.9419 97.1635 1.2216 152.6958 150.7086 1.9872 30.0 30.0 0.066 61.5 (0.7656) 15 96.0332 97.2277 1.1945 155.9939 154.1273 1.8666 30.0 30.0 0.062 64.0 (0.6721) 16 96.0090 97.1090 1.1000 153.8696 152.2021 1.6675 30.0 30.0 0.056 66.0 (0.5675) 17 94.1096 95.1113 1.0017 153.0828 151.4900 1.5928 30.0 30.0 0.053 62.9 (0.5911) 18 96.1963 97.4050 1.2087 155.4613 153.8812 1.5801 30.0 30.0 0.053 76.5 (0.3714) 
3-16

TABLE 3-10. TEST RESULTS FOR CONFIGURATION 10 

Weight of 

Blotter Paper 

Weight of Spray 

Water Used Test 

No. Before After 

Amount 

of Water 

Collected 

(g) Before After 

Amount 

of Water 

Used 

(g) 

Max. 

Inlet 

Pres. 

(′′H O) 2

Min. 

Inlet 

Pres. 

(′′H O) 2

Inlet 

Pres. 

(′′H O) 2

Spray 

Pressure

(psig) 

Spray 

Duration

(s) 

Rate 

of 

Spray

(g/s) 

Collection Efficiency

(%) 

Water 

Lost/Gain

(g) 

1 13.4142 15.9662 2.5520 89.1792 85.7363 3.4429 11.3 -10.8 22.1 30.0 30.0 0.115 74.1 (0.8909)2 12.7970 15.3091 2.5121 91.0011 87.5954 3.4057 11.2 -10.6 21.8 30.0 30.0 0.114 73.8 (0.8936)3 13.4556 15.7246 2.2984 89.7038 86.3151 3.3887 11.7 -11.3 23.0 30.0 30.0 0.113 67.8 (1.0903)4 12.7851 15.2288 2.4437 90.5060 87.2306 3.2754 11.8 -11.3 23.1 30.0 30.0 0.109 74.6 (0.8317)5 12.7578 14.9700 2.4220 94.3897 91.0230 3.3667 11.2 -10.6 21.8 30.0 30.0 0.112 71.9 (0.9447)6 12.8112 15.2537 2.4425 91.7995 88.4635 3.3360 11.5 -11.1 22.6 30.0 30.0 0.111 73.2 (0.8935)7 12.8031 15.2263 2.4232 88.1160 84.8276 3.2884 11.3 -11.1 22.4 30.0 30.0 0.110 73.7 (0.8652)
3-17

TABLE 3-11. TEST RESULTS FOR CONFIGURATION 11 

Weight of 

Blotter Paper 

Amount 

of Water 

Collected 

Weight of 

Spray Water Used 

Amount 

of Water 

Used 

Max. 

Inlet 

Pres. 

Min. 

Inlet 

Pres. 

Inlet 

Pres. 

Spray 

Pressure

Spray 

Duration 

Rate of 

Spray

Collection Efficiency

Water 

Lost/Gain Test 

No. Before After (g) Before After (g) (′′H O) 2 (′′H O) 2 (′′H O) 2 (psig) (s) (g/s) (%) (g) 

1 12.7233 15.2759 3.4545 90.4544 87.1259 3.3285 9.4 -9.1 18.5 30.0 30.0 0.111 103.79 0.1260 

31.4780 32.3799 0.9019 

2 12.7865 15.2026 3.1425 95.2973 91.9151 3.3822 9.9 -9.5 19.4 30.0 30.0 0.113 92.91 (0.2397) 

32.9290 33.4448 34.1712 0.7264 

3 12.7897 15.2007 2.7768 91.8721 88.4753 3.3968 9.6 -9.1 18.7 30.0 30.0 0.113 81.75 (0.6200) 

31.2636 31.4627 31.8285 0.3658 

4 12.0063 14.3466 2.5793 88.4553 85.0991 3.3562 9.6 -9.1 18.7 30.0 30.0 0.112 76.85 (0.7769) 

31.8300 32.0690 0.2390 

5 12.5784 14.8952 2.5773 94.7245 91.3118 3.4127 9.6 -9.1 18.7 30.0 30.0 0.114 75.52 (0.8354) 

32.0454 32.3059 0.2605 

6 12.7919 15.2340 2.4899 91.2668 87.8380 3.4288 9.6 -9.1 18.7 30.0 30.0 0.114 72.62 (0.9389) 

32.3044 32.3522 0.0478 

7 13.5364 15.9106 3.3628 92.3908 89.0787 3.3121 9.2 -9.1 18.3 30.0 30.0 0.110 101.53 0.0507 

31.9156 32.9042 0.9886 

8 13.2310 15.7681 3.0775 92.2712 88.8557 3.4155 9.2 -9.1 18.3 30.0 30.0 0.114 90.10 (0.3380) 

32.9135 33.4300 0.5165 

9 13.6218 16.0725 3.9985 90.7020 87.2636 3.4384 7.2 -7.1 14.3 30.0 30.0 0.115 116.29 0.5601 

31.0876 32.6354 1.5478 

10 15.5247 17.5451 2.8492 93.3074 90.5095 2.7979 9.2 -9.1 18.3 30.0 30.0 0.093 101.83 0.0513 

25.4582 26.2870 0.8288 

11 15.5619 18.0647 3.4573 93.6995 90.2215 3.4780 9.2 -9.1 18.3 30.0 30.0 0.116 99.40 (0.0207) 

25.2990 26.2535 0.9545 
3-18

TABLE 3-11. TEST RESULTS FOR CONFIGURATION 11 (Continued) 

Weight of 

Blotter Paper 

Amount 

of Water 

Collected 

Weight of 

Spray Water Used 

Amount 

of Water 

Used 

Max. 

Inlet 

Pres. 

Min. 

Inlet 

Pres. 

Inlet 

Pres. 

Spray 

Pressure

Spray 

Duration

Rate of 

Spray 

Collection Efficiency

Water 

Lost/Gain Test 

No. Before After (g) Before After (g) (′′H O) 2 (′′H O) 2 (′′H O) 2 (psig) (s) (g/s) (%) (g) 

12 13.4264 15.8812 2.8993 92.7945 89.4416 3.3529 9.2 -9.1 18.3 30.0 30.0 0.112 86.47 (0.4536) 

21.6976 22.1421 0.4445 

13 22.3579 25.0711 3.0533 90.1501 86.4393 3.7108 7.3 -8.0 15.3 30 30 0.124 82.28 (0.6575) 

27.4553 27.7954 0.3401 

14 22.3884 25.0186 3.2813 91.2187 87.5604 3.6583 7.3 -8.0 15.3 30 30 0.122 89.69 (0.3770) 

27.9241 28.5752 0.6511 

15 28.5012 30.7736 3.1963 90.7473 87.0511 3.6962 7.5 -8.1 15.6 30 30 0.123 86.48 (0.4999) 

27.0338 27.8002 0.7664 

16 27.8787 30.5173 2.9763 91.1969 87.5831 3.6138 7.0 -7.9 14.9 30 30 0.120 82.36 (0.6375) 

27.7738 28.1115 0.3377 

17 22.3622 24.7696 2.8153 91.5502 87.6187 3.9315 6.6 -7.6 14.2 30 30 0.131 71.61 (1.1162) 

27.5213 27.9292 0.4079 
3-19

TABLE 3-12. TEST RESULTS FOR CONFIGURATION 11 MOD-I 

Weight of 

Blotter Paper 

Amount 

of Water 

Collected 

Weight of 

Spray Water Used

Amount 

of Water 

Used 

Max. 

Inlet 

Pres. 

Min. 

Inlet 

Pres. 

Inlet 

Pressure

Spray 

Pressure

Spray 

Duration

Rate 

of 

Spray

Collection Efficiency

Water 

Lost/Gain Test 

No. Before After (g) Before After (g) (′′H O) 2 (′′H O) 2 (′′H O) 2 (psig) (s) (g/s) (%) (g) 

1 15.5688 17.8289 3.1438 89.8168 86.5479 3.2689 12.4 -13.9 26.3 30.0 30.0 0.109 96.17 (0.1251)

24.7006 25.5843 0.8837 

2 15.5860 18.0332 3.2881 92.3648 89.0383 3.3265 12.2 -13.6 25.8 30.0 30.0 0.111 98.85 (0.0384)

24.6937 25.5346 0.8409 

3 15.6233 18.1434 3.4344 94.2287 90.8196 3.4091 12.0 -13.5 25.5 30.0 30.0 0.114 100.74 0.0253 

25.0776 25.9919 0.9143 

4 22.6262 25.2639 3.7169 91.6015 88.1430 3.4585 11.6 -12.8 24.4 20.0 30.0 0.115 107.47 0.2584 

25.0406 26.1198 1.0792 

5 15.5512 18.0412 3.3544 91.0175 87.6553 3.3622 12.5 -13.8 26.3 20.0 37.0 0.091 99.77 (0.0078)

24.8587 25.7231 0.8644 

6 15.3753 17.8673 3.4518 91.1967 87.8597 3.3370 12.3 -13.6 25.9 20.0 37.0 0.090 103.44 0.1148 

25.6037 26.5635 0.9598 

7 15.6317 18.1301 3.3795 91.3433 87.9744 3.3689 12.2 -13.6 25.8 20.0 37.0 0.091 100.31 0.0106 

25.3452 26.2263 0.8811 
3.5 TESTS WITH WATER COLLECTOR CONFIGURATION 11 MOD-I.

The preliminary tests discussed in section 3.4 showed that collection efficiencies within 100% 

could be attained with configuration 11 Mod-I. However, the results were based on a small 

range of water spray rates; hence, accuracy of the technique could not be ascertained. Further 

tests were, therefore, conducted over a wider range of conditions, including those normally found 

in icing wind tunnels, i.e., LWC between 0.1 to 3 g/m3

. 

To relate the test measurements to icing cloud conditions, the water spray rate was converted into 

LWC with the following expression: 

 LWC (based on water sprayed or collected, g/m3)=Rate of water sprayed or collected (g/s) (3-1) 

Probe inlet volumetric flow (m3/s) 

The volumetric flow was calculated from the following equation: 

Probe inlet volumetric flow (m3/s) = × Δ×

ρ

π D 2 P

4

2

Discharge coefficient (3-2) 

where 

D – inner diameter of the 90 degree elbow tube (0.022 m or 0.866 inch) 

ΔP – inlet static pressure (Pa) 

ρ – flow density (kg/m3) 

Discharge coefficient – 1.0 (assumes a uniform velocity profile at the probe inlet) 

The LWC of the cloud entering the probe inlet was adjusted via changing the probe inlet air 

volumetric flow and amount of water sprayed. To reduce the probe air volumetric flow, a 

container with a small hole was installed downstream of the suction fan exhaust. Figure 3-17 

shows three such containers with different hole sizes. Figure 3-18 shows the installation of a 

container into the extension wand of the suction fan. 

 

Pressure loss 

device 

Extension pipe connected to 

suction fan exhaust 

FIGURE 3-17. PRESSURE LOSS 

DEVICES WITH THREE 

DIFFERENT OPENING SIZES 

FIGURE 3-18. INSTALLATION OF A 

PRESSURE LOSS DEVICE DOWNSTREAM 

OF THE SUCTION FAN 

3-20
The test procedure described in section 3.3 was altered to suit the probe efficiency tests with 

blotter paper tube and silica gel desiccants installed in the probe collector. The modified test 

procedures in section C.1 of appendix C describe the preparation of the container, water sample, 

blotter paper, silica gel, test methodology, and data analysis. A total of 65 tests were conducted 

and the results are shown in figures 3-19 to 3-21 and table 3-13. Tests 1 to 61 were conducted 

with approximately 3.3 g of water, and tests 62 to 65 were conducted with approximately 10.2 g 

of water. The following materials, settings, and test conditions were used: 

• Silica gel 7 to 8 g 

• Water used or sprayed 2.3 to 10.5 g 

• Spray brush air pressure setting 10 to 30 psig 

• Spray duration 30 to 130 s 

• Spray rate 0.029 to 0.350 g/s 

• LWC 0.54 to 8.5 g/m3

• Test duration 30 to 130 s 

02468

LWC based on wate

10

r collected (g/m3)

0

2

4

6

8

10

LWC based on water sprayed (g/m3)

Configuration no.11 Mod-I

Plastic container installed

Silica gel (7g to 8g) in B-Gon pouch 

Blotter tube (100mm) on divergent exit

Line of symmetry

02468

LWC based on water collected (g/m3)

10

0.4

0.6

0.8

1

1.2

1.4

Collection efficiency (%)

Configuration no.11 Mod-I

Plastic container installed

Silica gel (7 to 8g) in B-Gon pouch

Blotter tube (100m) on divergent exit

y

Collection efficiency (curve-fit)

FIGURE 3-19. LIQUID WATER CONTENT 

(Water Collected) VERSUS LWC (Water Sprayed)

FIGURE 3-20. LIQUID WATER CONTENT 

(Water Collected) VERSUS COLLECTION 

EFFICIENCY 

02468

LWC based on water collected (g/m3)

10

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Configuration no.11 Mod-I

Plastic container installed

Silica gel (7 to 8g) in B-Gon pouch

Blotter tube (100m) on divergent exit

Contrib. by blotter paper

Contrib. by silica gel and B-Gon

Co bu o s o e C

Contrib. by blotter paper (curve-fit)

Contrib. by B-Gon + silica gel (curve-fit)

FIGURE 3-21. CONTRIBUTIONS TO COLLECTION EFFICIENCY BY BLOTTER PAPER 

AND SILICA GEL 

3-21
TABLE 3-13. TEST RESULTS FOR CONFIGURATION 11 MOD-I (LABORATORY) 

Weight of 

Blotter Paper 

Weight of 

Spray Water Used 

Test No. Before After 

Amount 

of Water 

Collected

(g) Before After 

Amount of 

Water Used

(g) 

Maximum 

Inlet 

Pressure 

(′′H2O) 

Minimum 

Inlet 

Pressure 

(′′H2O) 

Inlet 

Pressure

(′′H2O)

1 15.5688 17.8289 3.1438 89.8168 86.5479 3.2689 12.4 -13.9 26.3 

24.7006 25.5843 0.8837 

2 15.5860 18.0332 3.2881 92.3648 89.0383 3.3265 12.2 -13.6 25.8 

24.6937 25.5346 0.8409 

3 15.6233 18.1434 3.4344 94.2287 90.8196 3.4091 12.0 -13.5 25.5 

25.0776 25.9919 0.9143 

4 22.6262 25.2639 3.7169 91.6015 88.1430 3.4585 11.6 -12.8 24.4 

25.0406 26.1198 1.0792 

5 15.5512 18.0412 3.3544 91.0175 87.6553 3.3622 12.5 -13.8 26.3 

24.8587 25.7231 0.8644 

6 15.3753 17.8673 3.4518 91.1967 87.8597 3.3370 12.3 -13.6 25.9 

25.6037 26.5635 0.9598 

7 15.6317 18.1301 3.3795 91.3433 87.9744 3.3689 12.2 -13.6 25.8 

25.3452 26.2263 0.8811 

8 22.3349 24.7527 3.0929 93.6698 90.3679 3.3019 14.5 -14.5 29.0 

25.9885 26.6636 0.6751 

9 22.3558 24.5944 3.0425 90.2834 87.0168 3.2666 14.7 -14.6 29.3 

25.4446 26.2165 0.7719 

10 22.2960 24.5680 3.1116 91.7500 88.4925 3.2575 14.4 -14.3 28.7 

25.2978 26.1374 0.8396 

11 22.2699 24.4771 3.0437 92.1807 88.9155 3.2652 14.5 -14.4 28.9 

25.7473 26.5838 0.8365 

12 22.3015 24.5598 2.8996 94.9600 91.7982 3.1618 5.5 -5.2 10.7 

25.3279 25.9692 0.6413 

13 22.2628 24.4916 2.9122 92.9389 89.7976 3.1413 5.5 -5.2 10.7 

25.4072 26.0906 0.6834 

14 22.2556 24.5488 2.9820 91.8690 88.6705 3.1985 5.5 -5.2 10.7 

25.5413 26.2301 0.6888 

15 22.3386 24.7124 3.1057 92.1532 88.9219 3.2313 5.6 -5.3 10.9 

25.7452 26.4771 0.7319 

16 22.6099 25.1166 3.2462 92.0454 88.7521 3.2933 5.6 -5.3 10.9 

25.5185 26.2580 0.7395 

17 22.5482 24.9960 3.1207 90.6261 87.3534 3.2727 5.5 -5.2 10.7 

25.9011 26.5740 0.6729 

18 22.4370 24.8238 3.2643 91.4187 88.2220 3.1967 5.5 -5.2 10.7 

25.7495 26.6270 0.8775 

19 22.5446 24.8305 3.1727 92.3731 89.2691 3.1040 5.6 -5.3 10.9 

25.5409 26.4277 0.8868 

20 22.3192 24.4856 3.0533 90.4450 87.4299 3.0151 5.6 -5.3 10.9 

25.2320 26.1189 0.8869 

21 22.3183 24.8441 3.2991 90.2764 86.8669 3.4095 6.7 -6.7 13.4 

25.6071 26.3804 0.7733 

3-22
TABLE 3-13. TEST RESULTS FOR CONFIGURATION 11 MOD-I 

(LABORATORY) (Continued) 

Spray 

Pressure 

(psig) 

Spray 

Duration 

(s) 

Rate of 

Spray 

(g/s) 

Collection 

Efficiency

(%) 

Water 

Lost/Gain

(g) 

LWC 

Water 

Collected

(g/m3

) 

LWC 

Water 

Sprayed

(g/m3) 

LWC (Collected) 

Contributed by 

Blotter 

(%) 

LWC (Collected) 

Contributed by 

Silica 

(%) 

30.0 30.0 0.109 96.17 (0.1251) 2.6715 2.7778 69.14 27.03 

30.0 30.0 0.111 98.85 (0.0384) 2.8211 2.8540 73.57 25.28 

30.0 30.0 0.114 100.74 0.0253 2.9639 2.9421 73.92 26.82 

20.0 30.0 0.115 107.47 0.2584 3.2792 3.0512 76.27 31.20 

20.0 37.0 0.091 99.77 (0.0078) 2.3112 2.3166 74.06 25.71 

20.0 37.0 0.090 103.44 0.1148 2.3966 2.3169 74.68 28.76 

20.0 37.0 0.091 100.31 0.0106 2.3510 2.3436 74.16 26.15 

20 37.0 0.089 93.67 (0.2090) 2.0294 2.1665 73.22 20.45 

10 67.0 0.049 93.14 (0.2241) 1.0968 1.1776 69.51 23.63 

10 67.0 0.049 95.52 (0.1459) 1.1334 1.1865 69.75 25.77 

10 67.0 0.049 93.22 (0.2215) 1.1048 1.1852 67.60 25.62 

30 30.0 0.105 91.71 (0.2622) 3.8630 4.2123 71.42 20.28 

30 30.0 0.105 92.71 (0.2291) 3.8798 4.1850 70.95 21.76 

30 30.0 0.107 93.23 (0.2165) 3.9728 4.2612 71.70 21.54 

20 37.0 0.087 96.11 (0.1256) 3.3239 3.4583 73.46 22.65 

20 37.0 0.089 98.57 (0.0471) 3.4743 3.5247 76.12 22.45 

20 37.0 0.088 95.36 (0.1520) 3.3710 3.5352 74.79 20.56 

10 67.0 0.048 102.11 0.0676 1.9473 1.9069 74.66 27.45 

10 67.0 0.046 102.21 0.0687 1.8752 1.8346 73.64 28.57 

10 67.0 0.045 101.27 0.0382 1.8046 1.7820 71.85 29.42 

30 30.0 0.114 96.76 (0.1104) 3.9276 4.0590 74.08 22.68 

3-23
TABLE 3-13. TEST RESULTS FOR CONFIGURATION 11 MOD-I (LABORATORY) 

(Continued) 

Weight of 

Blotter Paper 

Weight of 

Spray Water Used 

Test No. Before After 

Amount 

of Water 

Collected

(g) Before After 

Amount of 

Water Used

(g) 

Maximum 

Inlet 

Pressure 

(′′H2O) 

Minimum 

Inlet 

Pressure 

(′′H2O) 

Inlet 

Pressure 

(′′H2O) 

22 22.2962 24.6077 3.1680 91.0307 87.6700 3.3607 7.5 -7.5 15.0 

25.5680 26.3570 0.7890 

23 22.3629 25.0705 3.4673 91.1422 87.6435 3.4987 7.8 -7.8 15.6 

25.2942 26.0539 0.7597 

24 22.3611 25.0380 3.5454 91.5624 88.0732 3.4892 7.4 -7.3 14.7 

25.4527 26.3212 0.8685 

25 22.4764 25.1375 3.3985 92.2427 88.6357 3.6070 7.7 -7.7 15.4 

25.4726 26.1960 0.7234 

26 22.4701 24.7877 3.0977 90.9700 87.4971 3.4729 7.5 -7.5 15.0 

25.6101 26.3057 0.6956 

27 22.3974 24.8870 3.1237 93.0954 89.8173 3.2781 7.6 -7.6 15.2 

26.3957 27.0298 0.6341 

28 22.2380 24.5959 3.0635 93.5992 90.1830 3.4162 7.6 -7.6 15.2 

25.8044 26.5100 0.7056 

29 22.3100 24.7402 3.0844 91.4531 88.2566 3.1965 7.6 -7.6 15.2 

26.4779 27.1321 0.6542 

30 22.3623 24.7840 3.1299 93.0510 89.7886 3.2624 7.8 -7.8 15.6 

26.7926 27.5008 0.7082 

31 22.2598 24.5958 2.8965 93.8918 90.4473 3.4445 7.5 -7.9 15.4 

26.5838 27.0328 0.4490 

32 22.5484 24.8430 2.8907 90.0863 86.8320 3.2543 7.4 -7.8 15.2 

25.5120 26.1081 0.5961 

33 22.4556 25.0857 3.4622 91.4359 87.8933 3.5426 7.5 -8.1 15.6 

27.5893 28.4214 0.8321 

34 22.3454 24.9776 3.4117 90.8259 87.2619 3.5640 7.2 -7.8 15.0 

27.5796 28.3591 0.7795 

35 22.8182 25.4166 3.3176 92.0822 88.4285 3.6537 6.5 -7.5 14.0 

27.7525 28.4717 0.7192 

36 27.0432 28.7130 3.1549 91.9030 88.9507 2.9523 11.5 -13.7 25.2 

27.0615 28.5466 1.4851 

37 26.4434 28.1492 3.2608 91.1095 88.1906 2.9189 12.1 -14.5 26.6 

27.1909 28.7459 1.5550 

38 26.5722 28.0280 2.9137 91.6892 88.7763 2.9129 12.0 -14.5 26.5 

27.9431 29.4010 1.4579 

39 26.4329 28.2429 3.1656 91.5830 88.3442 3.2388 4.0 -6.3 10.3 

27.5388 28.8576 1.3188 

40 26.5560 28.7413 3.5377 92.2566 88.6053 3.6513 4.0 -6.3 10.3 

27.7740 29.0547 1.2807 

41 26.3664 28.5951 3.4837 91.8112 88.2383 3.5729 6.4 -8.8 15.2 

27.3045 28.5595 1.2550 

42 26.6254 28.8670 3.4947 93.2096 89.5179 3.6917 6.5 -8.9 15.4 

27.1811 28.4180 1.2369 

43 26.6950 28.9521 3.6575 92.8535 89.2188 3.6347 12.0 -15.0 27.0 

27.1707 28.5436 1.3729 

3-24
TABLE 3-13. TEST RESULTS FOR CONFIGURATION 11 MOD-I 

(LABORATORY) (Continued) 

Spray 

Pressure 

(psig) 

Spray 

Duration 

(s) 

Rate of 

Spray 

(g/s) 

Collection 

Efficiency

(%) 

Water 

Lost/Gain

(g) 

LWC 

Water 

Collected

(g/m3

) 

LWC 

Water 

Sprayed

(g/m3) 

LWC (Collected) 

Contributed by 

Blotter 

(%) 

LWC (Collected) 

Contributed by 

Silica 

(%) 

30 30.0 0.112 94.27 (0.1927) 3.5647 3.7815 70.79 23.48 

30 30.0 0.117 99.10 (0.0314) 3.8257 3.8603 77.39 21.71 

30 30.0 0.116 101.61 0.0562 4.0298 3.9660 76.72 24.89 

30 30.0 0.120 94.22 (0.2085) 3.7741 4.0056 74.16 20.06 

30 30.0 0.116 89.20 (0.3752) 3.4856 3.9078 69.17 20.03 

30 30.0 0.109 95.29 (0.1544) 3.4916 3.6642 75.95 19.34 

30 30.0 0.114 89.68 (0.3527) 3.4243 3.8186 69.02 20.65 

30 30.0 0.107 96.49 (0.1121) 3.4477 3.5730 76.03 20.47 

30 30.0 0.109 95.94 (0.1325) 3.4534 3.5996 74.23 21.71 

30 30.0 0.115 84.09 (0.5480) 3.2166 3.8251 71.06 13.04 

30 30.0 0.108 88.83 (0.3636) 3.2312 3.6376 70.51 18.32 

30 30 0.118 97.73 (0.0804) 3.8201 3.9088 74.24 23.49 

30 30 0.119 95.73 (0.1523) 3.8389 4.0103 73.86 21.87 

30 30 0.122 90.80 (0.3361) 3.8640 4.2555 71.12 19.68 

30 100.0 0.030 106.86 0.2026 0.8217 0.7689 56.56 50.30 

30 100.0 0.029 111.71 0.3419 0.8266 0.7399 58.44 53.27 

30 100.0 0.029 100.03 0.0008 0.7400 0.7398 49.98 50.05 

30 100.0 0.032 97.74 (0.0732) 1.2896 1.3194 57.02 40.72 

30 100.0 0.037 96.89 (0.1136) 1.4411 1.4874 61.81 35.08 

30 100.0 0.036 97.50 (0.0892) 1.1682 1.1981 62.38 35.13 

30 100.0 0.037 94.66 (0.1970) 1.1643 1.2299 61.16 33.50 

30 80.0 0.045 100.63 0.0228 1.1503 1.1431 62.86 37.77 

3-25
TABLE 3-13. TEST RESULTS FOR CONFIGURATION 11 MOD-I 

(LABORATORY) (Continued) 

Weight of 

Blotter Paper 

Weight of 

Spray Water Used 

Test No. Before After 

Amount 

of Water 

Collected

(g) Before After 

Amount of 

Water Used

(g) 

Maximum 

Inlet 

Pressure 

(′′H2O) 

Minimum 

Inlet 

Pressure 

(′′H2O) 

Inlet 

Pressure 

(′′H2O) 

44 26.7202 28.6398 3.2964 91.6539 88.5355 3.1184 12.1 -15.0 27.1 

27.4055 28.7538 1.3483 

45 26.7468 28.8388 3.7890 91.1942 87.7828 3.4114 12.0 -15.0 27.0 

27.0082 28.6876 1.6794 

46 26.6600 28.6424 3.5677 90.9538 87.7214 3.2324 12.1 -15.2 27.3 

27.2038 28.7891 1.5853 

47 26.6331 28.6353 3.3707 90.2473 86.9877 3.2596 12.3 -15.2 27.5 

27.4081 28.7766 1.3685 

48 26.4837 28.4393 3.2617 92.2983 89.0852 3.2131 6.3 -9.0 15.3 

26.9412 28.2123 1.2711 

49 26.6776 28.7844 3.7269 92.6550 89.3006 3.3544 6.4 -9.2 15.6 

26.9905 28.5808 1.5903 

50 26.6448 28.5885 3.5464 93.6955 90.4469 3.2486 6.4 -9.2 15.6 

26.9318 28.4959 1.5641 

51 26.8083 29.0137 4.3430 90.6180 86.6224 3.9956 12.1 -16.4 28.5 

45.5807 47.6782 2.0975 

52 26.5445 28.4124 4.0124 91.8483 88.0613 3.7870 12.2 -15.5 27.7 

45.3925 47.5031 2.1106 

53 26.6975 28.3902 3.6437 92.0927 88.8650 3.2277 12.3 -15.7 28.0 

45.3158 47.2668 1.9510 

54 26.7345 28.3347 3.5155 92.7000 89.5489 3.1511 12.3 -15.7 28.0 

45.2429 47.1582 1.9153 

55 26.7194 28.4632 3.7595 91.8851 88.6200 3.2651 12.3 -15.7 28.0 

45.8189 47.8346 2.0157 

56 26.6343 27.6522 2.8393 90.1849 87.9273 2.2576 12.0 -15.7 27.7 

26.3984 28.2198 1.8214 

57 26.4417 28.2730 3.7327 91.4531 87.9541 3.4990 14.4 -13.5 27.9 

26.4956 28.3970 1.9014 

58 26.6189 28.2249 3.5154 90.6967 87.4389 3.2578 14.4 -13.5 27.9 

26.2628 28.1722 1.9094 

59 26.6246 28.3311 3.6852 91.5442 88.0361 3.5081 14.4 -13.3 27.7 

26.4697 28.4365 1.9668 

60 26.9945 28.5768 4.0426 91.9648 88.4357 3.5291 13.2 -12.1 25.3 

26.3998 28.8601 2.4603 

61 26.6270 28.8145 4.4367 92.1136 88.3575 3.7561 14.5 -13.6 28.1 

26.3768 28.6260 2.2492 

62 41.2349 50.2305 10.0745 94.8204 84.5303 10.0887 12.6 -14.1 26.7 

 120.5952 121.6741 1.079 

63 46.2900 55.2753 10.0545 94.4919 83.9809 10.5110 12.8 -14.5 27.3 

 120.9411 122.0103 1.069 

64 41.8369 50.7041 9.9351 95.3860 85.1505 10.2355 12.8 -14.5 27.3 

 120.6013 121.6692 1.068 

65 39.5495 48.4962 10.031 95.5672 85.5684 9.9988 12.8 -14.4 27.2 

 120.7592 121.8431 1.084 

3-26
TABLE 3-13. TEST RESULTS FOR CONFIGURATION 11 MOD-I 

(LABORATORY) (Continued) 

Spray 

Pressure 

(psig) 

Spray 

Duration 

(s) 

Rate of 

Spray 

(g/s) 

Collection 

Efficiency

(%) 

Water 

Lost/Gain

(g) 

LWC 

Water 

Collected

(g/m3

) 

LWC 

Water 

Sprayed

(g/m3) 

LWC (Collected) 

Contributed by 

Blotter 

(%) 

LWC (Collected) 

Contributed by 

Silica 

(%) 

30 70.0 0.045 105.71 0.1780 1.1827 1.1188 62.47 43.24 

30 80.0 0.043 111.07 0.3776 1.1917 1.0729 61.84 49.23 

30 80.0 0.040 110.37 0.3353 1.1159 1.0110 61.33 49.04 

30 80.0 0.041 103.41 0.1111 1.0504 1.0158 61.42 41.98 

30 80.0 0.040 101.51 0.0486 1.3627 1.3424 61.95 39.56 

30 80.0 0.042 111.10 0.3725 1.5420 1.3879 63.70 47.41 

30 80.0 0.041 109.17 0.2978 1.4674 1.3441 61.02 48.15 

30 150.0 0.027 108.69 0.3474 0.7091 0.6523 56.20 52.50 

30 150.0 0.025 105.95 0.2254 0.6645 0.6271 50.22 55.73 

30 130.0 0.025 112.89 0.4160 0.6925 0.6134 52.44 60.45 

30 130.0 0.024 111.56 0.3644 0.6681 0.5989 50.78 60.78 

30 130.0 0.025 115.14 0.4944 0.7145 0.6205 53.41 61.73 

30 130.0 0.017 125.77 0.5817 0.5425 0.4314 45.09 80.68 

30 130.0 0.027 106.68 0.2337 0.7107 0.6662 52.34 54.34 

30 130.0 0.025 107.91 0.2576 0.6693 0.6203 49.30 58.61 

30 130.0 0.027 105.05 0.1771 0.7042 0.6703 48.98 56.06 

30 130.0 0.027 114.55 0.5135 0.8083 0.7056 44.84 69.71 

30 130.0 0.029 118.12 0.6806 0.8417 0.7126 58.24 59.88 

30 30 0.336 99.86 (0.0142) 8.4967 8.5087 89.17 10.69 

 

30 30 0.350 95.66 (0.4565) 8.3861 8.7669 85.48 10.17 

 

30 30 0.341 97.07 (0.3004) 8.2865 8.5371 86.63 10.43 

 

20 30 0.333 100.32 0.0318 8.3815 8.3550 89.48 10.84 

 

3-27
3.5.1 Findings. 

The collection efficiencies obtained varied from 84% to 126%. The inlet static pressures 

recorded during the tests varied from 0.37 to 1.06 psig (10.3′′ to 29.3′′ Hg). 

Figure 3-19 shows the comparison between the LWC based on the amount of water collected and 

used (sprayed). The results showed that most data laid on the line of symmetry, which represents 

equal amounts of water collected and sprayed. The test data for LWC in the range of 3.0 to 

4.0g/m3

 indicate that relatively less water was collected compared to the amount of water 

sprayed. This can also be seen in figure 3-20 where for LWC values between 3.0 and 4.0g/m3

; 

the probe collection efficiency was approximately 90%. Figure 3-21 shows the contributions of 

the blotter paper (indicated the red dots) and silica gel (indicated the blue squares) to the catch 

efficiency of the probe collector as a function of LWC (based on water collected). Each set of 

data was also curve-fitted with a log-based power curve, which shows good agreement with 

experimental data. The two fitted curves intersected at a collection efficiency of about 0.55. The 

results showed that the sum of the contributions (to the collection efficiency) of the blotter paper 

and silica gel (includes B-Gon fiber mesh) was nearly 1.0. In addition, the following 

characteristics were observed from the results in figure 3-21: 

• At LWC values between 0.5 and 1.0g/m3, the amount of water adsorbed by blotter paper 

was less than 50%, whereas silica gel (and B-Gon) adsorbed more than 50%. The 

average collection efficiency was slightly higher than 100%. 

• At LWC values between 1.0 and 2.0g/m3, the amount of water adsorbed by blotter paper 

was more than 65%, whereas silica gel (and B-Gon) adsorbed less than 30%. The 

average collection efficiency was slightly less than 100%. 

• At LWC values between 3.0 and 4.0g/m3, the amount of water adsorbed by blotter paper 

was about 70%, whereas silica gel (and B-Gon) adsorbed about 20%. The average 

collection efficiency was 90%. 

• At LWC values of approximately 8.5g/m3, the amount of water adsorbed by blotter paper 

was about 90%, whereas silica gel (and B-Gon) adsorbed about 10%. The average 

collection efficiency was 100%. 

The mean collection efficiency based on the data presented in table 3-13 was 100.8% and the 

standard deviation was 7.89%. 

3.5.2 Conclusions. 

It was concluded that configuration 11 Mod-I was an efficient water collector, where efficiencies 

of nearly 100% were attainable for LWC values between 0.54 and 8.5g/m3

. This configuration 

was installed in the WSU 7- by 10-ft wind tunnel for iso-kinetic tests, as described in section 4. 

3-28
4. EXPERIMENTAL INVESTIGATION IN A WIND TUNNEL WITH THE WATER 

COLLECTOR CONFIGURATION 11 MOD-I DESIGN. 

This section describes the experimental tests that were conducted in the WSU 7- x 10-ft Beech 

Memorial Low-Speed Wind Tunnel. The objective was to evaluate the iso-kinetic operation of 

the probe and to conduct a limited number of water collection tests. Prior to the wind tunnel 

tests, an ISFC system was developed and tested in the laboratory. Descriptions of the 

development of the ISFC system, experimental setup in the wind tunnel, and experimental results 

are given below. 

4.1 TEST FACILITY. 

The WSU wind tunnel is a single-return, closed circuit facility with a maximum speed of 

160 mph (235 ft/s), corresponding to a Reynolds number of 1.46 million per foot. The test 

section is 7 ft high by 10 ft wide by 12 ft long. Four screens located in the plenum chamber 

upstream of the test section were used for flow conditioning. The contraction ratio between the 

plenum and test sections is 6 to 1. The tunnel is equipped with a four-bladed, 11-ft diameter, 

variable pitch propeller, which is driven by a 1000-hp electric motor. Figure 4-1 shows the 

planview of the facility. 

N 

FIGURE 4-1. THE WSU 7- BY 10-ft WIND TUNNEL FACILITY 

4.2 PROBE INSTALLATION. 

The reference probe was installed at the center of the test section, as shown in figure 4-2. The 

base of the probe was secured to a 3- by 2-ft by 3/4-inch-thick plywood platform, and the whole 

assembly was bolted onto the tunnel turntable. A 7- by 8-ft H-type hollow steel frame (diameter 

1 inch) was attached to the tunnel floor and ceiling and was located upstream of the probe. The 

4-1
water spray brush was secured to a steel bracket with two ring clips (figure 4-3), and they, in 

turn, were secured to the horizontal bar of the H-frame with an adjustable bolt clamp. The steel 

bracket (and brush) could be adjusted horizontally while vertical movements involved adjusting 

the H-bar itself. These lateral movements enabled the alignment of the spray brush with the 

center of the probe inlet. The distance between the spray brush nozzle and probe inlet was set to 

approximately 1 1/2 inches. The tubing that supplied water to the spray brush was secured to the 

H-frame and tunnel walls before exiting through a hole that was located next to the entry door of 

the test section (figure 4-2). Figure 4-4 shows the connection of this tubing to a water supply 

bottle. A humidity sensor (Vaisala HMP233, accuracy ±1% RH) was also installed in the test 

section to record the RH in the air stream during experimental tests and was secured to the 

horizontal bar with a steel bracket, as shown in figure 4-5. Another humidity sensor 

(FisherBrand traceable hygrometer, cat.11-661-21, accuracy ±3% RH) was installed inside the 

reference probe, as shown in figure 4-6. This was placed centrally at approximately middistance between the plastic container exit and reference probe outlet port. 

Flow direction Flow direction 

Water supply line

to the spray 

FIGURE 4-2. INSTALLATION OF THE REFERENCE PROBE IN THE WSU 7- BY 10-ft 

WIND TUNNEL—FRONT VIEW 

Steel bracket

Spray brush 

Probe inlet

Water supply for

spray brush 

FIGURE 4-3. POSITION OF THE SPRAY 

BRUSH IN FRONT OF THE PROBE INLET 

FIGURE 4-4. WATER SUPPLY FOR THE 

SPRAY BRUSH 

4-2
Fisherbrand 

humidity sensor

Probe main 

body 

Probe base Vaisala humidity 

sensor

FIGURE 4-5. HUMIDITY SENSOR 

VAISALA 

FIGURE 4-6. HUMIDITY SENSOR INSIDE 

THE REFERENCE PROBE 

The room that housed the aerodynamic balance of the wind tunnel, which is located directly 

beneath the test section, was also used to house the suction fan, throttle valve, and data 

acquisition system (DAQ). The outlet of the reference probe was connected to the suction fan 

inlet with a long flexible hose via a hole in the tunnel floor, as shown in figures 4-7 and 4-8. 

Both the DAQ and throttle valve were parts of the ISFC system. Details of the ISFC system are 

described in section 4.3. 

Hose connects 

to reference 

probe

Suction fan 

inlet

Suction fan 

outlet

Flexible hose 

FIGURE 4-7. EXTENSION HOSE 

CONNECTS PROBE TO SUCTION FAN 

FIGURE 4-8. SUCTION FAN EXHAUST TO 

THROTTLE VALVE 

4.3 ISO-KINETIC FLOW CONTROL SYSTEM. 

The ISFC system consisted of a throttling valve, DAQ system, pressure transducers, and a 

computer program to control the closing and opening of the throttling valve. Iso-kinetic 

condition was attained when the flow velocity in the test section was equal to the probe inlet 

velocity. During this condition, the probe inlet static pressure was equal to the static pressure of 

the test section. Since the speed of the suction fan was fixed, it could not be adjusted to match 

the tunnel velocity. Thus, a throttling valve was used to change the volumetric airflow through 

the probe, hence adjusting the probe inlet velocity. The objective of the ISFC system, therefore, 

was to control the throttle valve opening area so that probe inlet velocity could be set equal to the 

free-stream velocity. Details of the ISFC system components follow. 

4-3
4.3.1 Throttling Valve. 

The throttling valve (BE3 PF150-513, RF Technologies Inc), figure 4-9, consisted of an internal 

elastomer shell enclosed by an outer body made from cast iron. The closing and opening of the 

shell is analogous to that of a pinch valve where a tube is being pressed by two metal plates to 

close or open the valve. A Posiflex electro-pneumatic positioner controlled the movements of 

these plates with a 4- to 20-mA control signal and a line air pressure of 100 psig. The inlet port 

diameter was 2 inches while the outlet port diameter was 3 inches. The inlet port was connected 

to the suction fan’s exhaust (figure 4-8) via a flexible hose. 

Throttle valve

Posiflex 

pneumatic 

controller Pressure supply 

to valve 

FIGURE 4-9. THROTTLE VALVE 

The dynamic characteristics of the ISFC system were obtained by performing probe inlet 

pressure measurements at different valve openings. Figure 4-10 shows the characteristics of the 

valve with three different flow blockages. The blockage was created by installing a container 

(with a cutout hole) downstream of the suction fan exhaust, as shown in figures 3-17 and 3-18. 

The diameter of the hole in the container determined the range of achievable probe inlet 

pressures (or velocities), e.g., with 70% blockage. The possible probe inlet pressures were 

between 0.1 and 0.3 psig, corresponding to inlet speeds in the range of 75 to 130 mph. These 

characteristic curves were needed to accommodate a range of wind tunnel velocities. 

-1.2 -1 -0.8 -0.6 -0.4 -0.2 0

Probe Inlet Pressure (psig)

4

6

8

10

12

14

16

Drive Current to Open/Close Valve (mA)

Test Conditions

Zero Blockage

50% Blockage

70% Blockage

FIGURE 4-10. PROBE INLET PRESSURE VERSUS VALVE DRIVING CURRENT 

4-4
4.3.2 The ISFC Software and Data Acquisition System. 

A National Instrument DAQ system, the SCXI-1001 (figure 4-11), was used to record static 

pressures, RH and temperatures, and to generate a drive current to actuate the throttle valve. The 

DAQ system was housed in the room beneath the wind tunnel test section, whereas the desktop 

computer (figure 4-11(d)) was located adjacent to the tunnel control room. The DAQ system 

was remotely connected to the computer via a 16-ft cable. The SCXI-1001 system has 96 

differential input channels, 6 analog channels, 32 digital input/output, and 6 strain-gauge 

channels. Static pressures were recorded with a pair of pressure transducers (DRUCK PTX7217, 

range 0-30 psig, 4-20 mA). The electric current output signals from these transmitters had to be 

converted into voltages by a signal-conditioning unit (SCC311, National Instrument Inc.) 

because the SCXI system was preconfigured to accept only voltage signal (±5V). The RH and 

temperature from the wind tunnel was recorded with the Vaisala HMP233 sensor (figure 4-5), 

whereas the Fisherbrand Traceable sensor (figure 4-6) was used inside the reference probe. The 

output signals from the Vaisala sensor were wired directly into the DAQ system, whereas the 

signals from the Fisherbrand sensor were connected via an RS323 port on the desktop computer 

due to the propriety nature of the output signals that prohibited direct connection to the DAQ 

system. 

FIGURE 4-11. DATA ACQUISITION SYSTEM (SCXI-1001) 

4-5
The ISFC software was developed using the LabView (V7.0) to record static pressures, RH, and 

temperatures. Figure 4-12 shows the front panel of the ISFC code. The software checked for 

iso-kinetic condition using the static pressures from the probe inlet and the wind tunnel in the 

following simple expressions: 

PTOTAL(probe) = PTOTAL (test section) (4-1) 

hence 

PSTATIC(probe) + PDYNAMIC(probe) = PSTATIC (test section) + PDYNAMIC(test section) 

at iso-kinetic condition 

PDYNAMIC(probe) = PDYNAMIC (test section) (4-2) 

therefore 

PSTATIC(probe) = PSTATIC (test section) (4-3) 

where 

PTOTAL = total (or stagnation) pressure 

PSTATIC = static pressure (recorded as gauge pressure by the DRUCK pressure transmitter) 

PDYNAMIC = dynamic pressure 

Probe static pressure 

(gauge) 

Test section static 

pressure (gauge) 

can be read-in from 

a DPI-610 

RH in wind tunnel 

test section 

Temperature in test 

section 

Indicate status of isokinetic condition 

Indicate status of 

valve movements 

Pressure differences 

between probe and 

test section 

Stop program 

History plot of 

probe RH 

Probe RH and temperature 

 from RS232 port 

Indicate status of 

drive current 

Drive current 

reading (mA) 

History plot of probe 

temperature 

Probe 

temperature 

Probe RH 

FIGURE 4-12. ISO-KINETIC FLOW CONTROL SOFTWARE 

4-6
Iso-kinetic condition was attained when the static pressures and, therefore, the dynamic pressures 

in the probe and wind tunnel were equal. Note that iso-kinetic condition can also be established 

using the dynamic pressures alone. If the flow was not iso-kinetic, the valve characteristics in 

figure 4-10 were used to adjust the opening area of the throttle valve until the required iso-kinetic 

condition was accomplished. The ISFC software was tested prior to the wind tunnel tests in a 

laboratory to ensure proper integration between the hardware (e.g., pressure transmitters, 

humidity sensor, etc.) and software. The ISFC development tests involved using a digital 

pressure indicator (DRUCK DPI-610 in figure 4-11(d)) to simulate static pressures in a wind 

tunnel, according to equation 4-3. The following steps were used to test the software: 

• Set simulated tunnel static pressure 

• Start ISFC software 

• Switched on suction fan, and run for a set duration 

• Stop suction fan (after the set duration has been reached) 

• Stop ISFC software and process data 

The software recorded the data from the pressure transmitters and humidity sensors every 1.11 

seconds and stored the data into a file in the following order (in free format): 

• Column 1: Run time (s) 

• Column 2: Ambient relative humidity (%RH) 

• Column 3: Relative humidity inside probe (%RH) 

• Column 4: Ambient temperature (°C) 

• Column 5: Temperature inside probe (°C) 

• Column 6: Static pressure of tunnel test section (psig) 

• Column 7: Probe inlet static pressure (psig) 

• Column 8: Integer value (1 indicates iso-kinetic, 0 indicates non-iso-kinetic) 

Graphical plots were generated from this output file as shown in figures 4-13 to 4-15, which 

provide static pressures, RH, and total air temperatures versus run time. Figure 4-13 indicates 

that iso-kinetic condition was attained at the probe inlet within 3 seconds of engaging the suction 

fan, followed by a rapid recovery to the initial conditions after disengaging the fan. It also 

showed that during iso-kinetic condition, the probe inlet static pressure reading was almost equal 

to the simulated tunnel static pressure. The RH inside the probe is shown in figure 4-14. The 

results shown in this figure indicate that the humidity exhibited rapid changes during the process 

of engaging and disengaging the suction fan. The temperature distribution, shown in figure 4-15, 

did not exhibit the characteristic rapid changes since it was not expected to vary significantly in 

the laboratory. 

4-7
0 100 200 300 400 500 600 700

Time (s)

-1

-0.8

-0.6

-0.4

-0.2

0

Static Pressure (psig)

 Simulated Test Conditions

Run duration = 600 s

Probe Inlet 

Static Pressure (psig)

Simulated Tunnel 

Static Pressure (psig)

Static Pressure recorded with ISFC System

Suction Off

Simulated Tunnel Pressure Off

Suction On

0 100 200 300 400 500 600 700

Time (s)

40

42

44

46

48

50

52

54

56

58

60

Relative Humidity (%)

 Simulated Test Conditions

Run duration = 600 s

RH inside Probe (%)

Ambient RH (%)

Relative Humidity recorded with ISFC System

Suction On Suction Off

FIGURE 4-13. STATIC PRESSURE 

PLOTS—LABORATORY 

FIGURE 4-14. RELATIVE HUMIDITY 

PLOTS—LABORATORY 

0 100 200 300 400 500 600 700

Time (s)

22

23

24

25

Temperature (oF)

 Simulated Test Conditions

Run duration = 600 s

Probe Temperature

Ambient Temperature

StaticTemperature recorded with ISFC System

Suction Off

Suction On

FIGURE 4-15. TEMPERATURE PLOTS—LABORATORY 

When the ISFC software was initiated in the laboratory tests, a sequence of events occurred 

between the various sensors and the DAQ system. This sequence of events is illustrated in 

figure 4-11 and is described in the following steps: 

a. A pair of pressure transmitters records the static pressures from both the tunnel test 

section and probe inlet. 

b. The pressure transmitters convert these pressures into voltages (±5 V) for the DAQ 

system. 

c. The DAQ converts these voltages into digital signals, which were then routed to the 

computer and read by the ISFC software. 

d. The software computes the difference between the two pressure readings and checks with 

a set tolerance of ±0.035 psig. If it is outside this tolerance, it calculates the amount of 

valve movement and converts this into the appropriate drive current (mA) via the DAQ 

system. 

4-8
e. This current (4 to 20 mA from the DAQ) operates the pneumatic controller that moves 

the valve. 

Steps a. to e. were repeated in a loop until iso-kinetic flow condition was achieved. Following 

the successful development of the ISFC system in the laboratory, the DAQ system and 

associated sensors were moved to the WSU 7- by 10-ft wind tunnel for iso-kinetic testing, as 

described in section 4.4. 

4.4 TEST PROCEDURE. 

The test procedure previously developed for the laboratory tests (see appendix C, section C.1) 

was enhanced to include additional procedures required for testing in a wind tunnel. This is 

written in (appendix C, section C.2). The procedural changes implemented included special 

features to suit the atmospheric pressure in the test section of the WSU (7- by 10-ft) wind tunnel. 

The walls of the test section have a number of built-in louvers that were exposed to the outside 

environmental conditions; therefore, the tunnel velocity was deduced from the dynamic pressure 

calculated from the tunnel’s own calibrated velocity chart. The tunnel crew denoted this 

dynamic pressure as the Q value, and the unit of measure in pounds per square foot (psf). 

Although there are static pressure measurements in the test section, they are combined with the 

static pressure in the plenum to obtain Q. 

For iso-kinetic calculations, this (Q) value was converted into static pressures (equation 4-3, 

section 4.3) and simulated with the DPI-610 digital pressure indicator (figure 4-16(e)) using the 

methodology described earlier in the testing of the ISFC software in the laboratory (section 

4.3.2). The tunnel operator read out the Q value to the ISFC system operator who then entered 

this value into the DPI-610. The ISFC software (figure 4-12) reads the value entered into the 

DPI-610 and treat this as the static pressure in the test section of the wind tunnel. The test 

procedures that were developed for the laboratory (section C.1, appendix C) had to be modified 

for the wind tunnel tests. The modified test procedure is shown in section C.2, appendix C 

(modifications are written in italics). The following summarizes the wind tunnel tests: 

• Prepare water sample, silica gel, B-Gon, and blotter tube and install into reference probe 

• Start ISFC software 

• Tunnel operator starts wind tunnel and reads out the Q value (psf) to the ISFC operator 

• ISFC operator enters the Q value into the DPI-610, thus setting the simulated tunnel static 

pressure 

• Switch on suction fan 

• Start water spray 

• Stop suction fan (after the set duration has been reached) 

• Stop wind tunnel and ISFC software, process data 

4-9
B-Gon 

pouch Plastic 

container 

(a) Preparation of B-Gon Pouch Filled With Silica Gel (b) Installation of B-Gon Into Plastic Container 

(c) Preparation of Blotter Tube (d) ISFC Operation and Control 

(e) Digital Pressure Indicator DPI-610 

FIGURE 4-16. PREPARATION OF THE REFERENCE PROBE AND ISFC CONTROL 

Figure 4-16 shows the preparation of the reference probe and ISFC control, figure 4-16(a) shows 

the B-Gon pouch being prepared for the plastic container, figure 4-16(b) shows the B-Gon pouch 

inside the plastic container, figure 4-16(c) shows the blotter tube and brass rings that were used 

to maintain the shape of the tube, figure 4-16(d) shows the operation and control of the ISFC 

software, and figure 4-16(e) shows the DPI-610 that was used to simulate the static pressure in 

the test section of a wind tunnel. 

4.5 TEST MEASUREMENTS. 

The reference LWC probe test program in the WSU wind tunnel was carried out during a 4-day 

period between July 29 and August 1, 2003. The installation of the reference probe and ISFC 

system were completed in the first day of the test program. The second day involved the 

assessment of the water spray brush in the wind tunnel and the structural integrity of the 

reference probe at a range of tunnel velocities. 

4-10
Two problems with the spray brush were discovered during the preliminary assessment: (1) 

water had entered the probe static pressure ports causing blockages to the pressure transmitters 

and (2) a continuous drip had developed in the spray brush. The first problem did not occur 

during laboratory tests (section 3) because the suction fan was always operating during these 

tests. However, it was discovered that if the suction fan was switched off while water was 

sprayed into the probe, blockage would occur. Water in the pressure lines was eventually 

cleared with compressed air. The second problem was solved by simply raising the height of the 

water bottle above the level of the floor. 

During the integrity test of the reference probe, it was discovered that the main body (of the 

probe) had detached itself from the base that was bolted to the plywood platform (figure 4-6). 

This had occurred at a tunnel velocity of approximately 140 mph (63m/s) or Q ≈ 50.4 psf 

(0.35 psi). This problem was solved by permanently joining the probe main body to the base 

with a solvent-based adhesive. As an added precaution, it was also decided to limit the 

maximum tunnel velocity to 130 mph (58 m/s) or Q ≈ 43.2 psf (0.30 psi). Iso-kinetic and water 

collection efficiency tests were conducted in the last two days of the test program. Prior to these 

tests, the appropriate characteristics of the throttle valve in the wind tunnel had to be established 

because of the low tunnel velocities or (Q values). It was found that the suction fan with a 70% 

blockage (figure 4-10) was capable of providing the range of probe velocities required to match 

the tunnel velocities. 

The results are shown in figures 4-17 and 4-18 and table 4-1. Tests 1 to 17 were conducted with 

the wind tunnel on, and tests 18 to 20 represent static spray tests that were also conducted in the 

wind tunnel but the wind tunnel was off (i.e., zero airspeed). Appendix D shows plots of static 

pressures, RH, and temperatures for tests 1 to 20. The following test conditions were used: 

• Water used or sprayed 0.67 to 2.9 g 

• Spray brush pressure setting 25 to 50 psig 

• Spray duration 130 s 

• Spray rate 0.0051 to 0.0224 g/s 

• LWC 0.14 to 0.79 g/m3

• Test duration 130 s 

0 0.5 1 1.5 2 2.5

LWC based on water collected (g/m3)

3

0

0.5

1

1.5

2

2.5

3

LWC based on water sprayed (g/m3)

Configuration no.11 Mod-I

Plastic container installed

B-Gon mesh

Blotter tube (100mm) on divergent exit

Expt. Data (Tunnel in operation)

Expt. Data (Tunnel not in operation)

Line of symmetry

0 0.5 1 1.5 2 2.5 3

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Collection efficiency (%)

LWC based on water collected (g/m3)

Configuration no.11 Mod-I

Plastic container installed

Silica gel in B-Gon pouch 

Blotter tube (100m) on divergent exit

Expt. Data (Tunnel in operation)

Expt. Data (Tunnel not in operation)

Collection efficiency curve-fit

(config#11 Mod-I)

FIGURE 4-17. COMPARISON BETWEEN 

LWCs BASED ON WATER 

COLLECTED AND SPRAYED 

FIGURE 4-18. LIQUID WATER 

CONTENT VERSUS 

COLLECTION EFFICIENCY 

4-11
TABLE 4-1. TEST RESULTS FOR CONFIGURATION 11 MOD-I (WIND TUNNEL) 

Weight of 

Blotter Paper 

Weight of 

Spray Water Used Test 

No. Before After 

Amount of 

Water 

Collected 

(g) Before After 

Amount of 

Water 

Used 

(g) 

Inlet 

Pressure 

(psig) 

Spray 

Pressure 

(psig) 

1 26.5380 26.7387 0.9924 139.7827 136.6169 3.1658 0.20 50 

26.7995 27.5912 0.7917 

2 26.4162 27.4820 0.8425 136.6139 133.6964 2.9175 0.20 50 

26.8897 26.6664 -0.2233 

3 26.3796 26.4871 0.6401 133.6949 130.9292 2.7657 0.25 50 

26.6339 27.1665 0.5326 

4 26.4268 26.5365 0.6856 130.9282 128.1402 2.7880 0.25 50 

26.8324 27.4083 0.5759 

5 26.5098 26.4621 0.4177 128.1390 125.4819 2.6571 0.30 50 

26.9385 27.4039 0.4654 

6 26.3865 26.3243 0.4266 125.4802 122.7861 2.6941 0.30 50 

26.7569 27.2457 0.4888 

7 26.5069 26.4530 0.6969 119.2784 117.6788 1.5996 0.20 50 

26.5893 27.3401 0.7508 

8 26.5527 26.4508 0.5670 117.7110 116.1017 1.6093 0.20 50 

26.7576 27.4265 0.6689 

9 26.6245 26.4878 0.5108 116.0941 114.5026 1.5915 0.25 50 

26.8820 27.5295 0.6475 

10 26.4907 26.3445 0.5084 114.4993 112.9259 1.5734 0.25 50 

26.4684 27.1230 0.6546 

11 26.6495 26.5003 0.5070 112.9178 111.9098 1.0080 0.20 35 

26.7335 27.3897 0.6562 

12 26.4151 26.2761 0.5030 111.9080 110.8483 1.0597 0.25 35 

26.7071 27.3491 0.6420 

13 26.3765 26.2180 0.3974 110.8455 109.7392 1.1063 0.30 35 

26.6949 27.2508 0.5559 

14 26.5009 26.3567 0.5059 109.7380 109.0791 0.6589 0.20 25 

26.6838 27.3339 0.6501 

15 26.4478 26.2983 0.5495 109.0580 108.3780 0.6800 0.25 25 

26.6458 27.3448 0.6990 

16 26.4315 26.2641 0.3895 108.3748 107.6608 0.7140 0.30 25 

26.7504 27.3073 0.5569 

17 26.4541 26.3278 0.5211 107.6581 106.9656 0.6925 0.30 25 

26.6889 27.3363 0.6474 

18 26.4160 26.8135 1.7639 122.6318 119.7889 2.8429 0.20 50 

26.9036 28.2700 1.3664 

19 26.5445 26.9524 1.8615 122.6224 120.8334 1.7890 0.20 50 

26.8788 28.3324 1.4536 

20 26.4325 26.6972 1.7332 120.9156 119.2840 1.6316 0.20 50 

26.8776 28.3461 1.4685 

4-12
TABLE 4-1. TEST RESULTS FOR CONFIGURATION 11 MOD-I 

(WIND TUNNEL) (Continued) 

Spray 

Duration 

(s) 

Rate of 

Spray 

(g/s) 

Collection 

Efficiency 

(%) 

Water 

Lost/Gain 

(g) 

LWC 

Water 

Collected

(g/m3) 

LWC 

Water 

Sprayed 

(g/m3) 

LWC Collected 

Contributed by 

Blotter 

(%) 

LWC Collected 

Contributed by 

Silica 

(%) 

130.0 0.024 31.35 (2.1734) 0.4241 1.3529 6.34 25.01 

130.0 0.022 28.88 (2.0750) 0.3600 1.2468 36.53 -7.65 

130.0 0.021 23.14 (2.1256) 0.2447 1.0571 3.89 19.26 

130.0 0.021 24.59 (2.1024) 0.2621 1.0657 3.93 20.66 

130.0 0.020 15.72 (2.2394) 0.1457 0.9271 -1.80 17.52 

130.0 0.021 15.83 (2.2675) 0.1489 0.9401 -2.31 18.14 

130.0 0.012 43.57 (0.9027) 0.2978 0.6836 -3.37 46.94 

130.0 0.012 35.23 (1.0423) 0.2423 0.6877 -6.33 41.56 

130.0 0.012 32.10 (1.0807) 0.1952 0.6083 -8.59 40.68 

130.0 0.012 32.31 (1.0650) 0.1943 0.6014 -9.29 41.60 

130.0 0.008 50.30 (0.5010) 0.2167 0.4308 -14.80 65.10 

130.0 0.008 47.47 (0.5567) 0.1923 0.4051 -13.12 60.58 

130.0 0.009 35.92 (0.7089) 0.1387 0.3860 -14.33 50.25 

130.0 0.005 76.78 (0.1530) 0.2162 0.2816 -21.88 98.66 

130.0 0.005 80.81 (0.1305) 0.2100 0.2599 -21.99 102.79 

130.0 0.005 54.55 (0.3245) 0.1359 0.2491 -23.45 78.00 

130.0 0.005 75.25 (0.1714) 0.1818 0.2416 -18.24 93.49 

130.0 0.022 62.05 (1.0790) 0.7538 1.2149 13.98 48.06 

130.0 0.014 104.05 0.0725 0.7955 0.7645 22.80 81.25 

130.0 0.013 106.23 0.1016 0.7407 0.6973 16.22 90.00 

4-13
4.6 RESULTS AND DISCUSSIONS. 

The collection efficiencies obtained during the wind tunnel test varied from 15% to 81% for runs 

1 to 17 and from 62% to 106% for test runs 18 to 20. The inlet static pressures recorded during 

these tests varied from 0.2 to 0.3 psi (5.5 to 8.3 in. of water). A limited range of LWC intensities 

were considered in the wind tunnel investigation. It was not possible to conduct tests over a 

wider range of LWC because of the limited resources allocated for wind tunnel tests. 

Figure 4-17 shows that for tests 1 to 17, the amount of water collected was much lower than that 

sprayed into the reference probe. Therefore, the probe collection efficiencies were also well 

below the maximum value of 100%, as shown in figure 4-18. The main cause of these poor 

results was the significant amount of water lost through evaporation during the tests. Typical RH 

and temperatures that were recorded in the wind tunnel for all the experimental tests are shown 

in figures 4-19 and 4-20 respectively. In a normal test lasting only 130 seconds, the tunnel RH 

decreased from about 28% to 20% (indicated by the blue dots in figure 4-19), while tunnel total 

temperature increased from about 97° to 108°F (36° to 42°C, indicated by blue dots in 

figure 4-20). The RH recorded inside the probe decreased from 35% to 33% (indicated by the 

red dots in figure 4-19) and the temperature increased from 97° to 108°F (36° to 43°C, indicated 

by red dots in figure 4-20). These measurements were different from those recorded during the 

spray tests with the tunnel off, tests 18 to 20. Figure 4-21 shows that the RH recorded inside the 

probe increased from 43% to 46%, whereas figure 4-22 indicates that the temperature decreased 

from 86° to 82°F (30° to 28°C). The tunnel RH and temperature recorded during these tests 

remained fairly constant at 41% and 85°F (29.3°C), respectively. Therefore, collection 

efficiencies within 100% were obtained for these tests, except in test 18 where the probe water 

collection efficiency was 62%. However, these results were consistent with those conducted in 

the laboratory (section 3.5). The evaporation effects shown in table 4-1 where water evaporation 

from the dry blotter paper was observed (based on weight measurements of the blotter before and 

after the test) were recorded in tests 5 to 17, while water adsorption by the paper was observed 

during spray tests 18 to 20. 

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 2

Run duration = 130 s

Probe inlet static press. = 0.2 psig

LWC (approx.) = 1.25 g/m3

TWC probe

Wind Tunnel

y

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 2

Run duration = 130 s

Probe inlet static press. = 0.2 psig

LWC (approx.) = 1.25 g/m3

TWC probe

Wind Tunnel

p

FIGURE 4-19. PROBE AND TUNNEL 

RH DISTRIBUTION—WIND TUNNEL 

IN OPERATION 

FIGURE 4-20. PROBE AND TUNNEL 

TEMPERATURE DISTRIBUTION— 

WIND TUNNEL IN OPERATION 

4-14
0 100 200 300 400 500 600

Time (s)

40

42

44

46

48

50

Relative humidity (%)

 Test number 18

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 1.22 g/m3

TWC probe

Wind Tunnel

y

Line indicates Suction Off

Line indicates Suction On

0 100 200 300 400 500 600

Time (s)

26

28

30

32

34

Temperature (oC)

 Test number 18

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 1.22 g/m3

TWC probe

Wind Tunnel

p

Line indicates Suction Off

Line indicates Suction On

FIGURE 4-21. PROBE AND TUNNEL RH 

DISTRIBUTION—STATIC SPRAY TEST 

FIGURE 4-22. PROBE AND TUNNEL 

TEMPERATURE DISTRIBUTION— 

STATIC SPRAY TEST 

Iso-kinetic conditions were accomplished in all the experimental tests for tunnel velocities 

between 105 and 130 mph (47 to 58 m/s, Q 28.8 to 43.2 psf). Typical static pressure 

measurements at the probe inlet are shown in figures 4-23 (test 2) and 4-24 (test 18). These two 

test points were selected because the test conditions and amount of water sprayed (or used) were 

similar, although test 2 was conducted while the wind tunnel was operating, whereas for test 18, 

the tunnel was off. Figure 4-23 shows that prior to switching on the suction fan, a ramp pressure 

had developed inside the reference probe. Upon switching the fan on the static pressure 

decreased rapidly and iso-kinetic flow was attained in less than 3 seconds. The drift in the probe 

inlet static pressure was due primarily to the unstable aerodynamic performance of the suction 

fan at low volumetric flows, which was created by blocking 70% of the fan exhaust flow (figure 

4-10). However, the ISFC software was able to adjust the throttle valve and maintained isokinetic condition. The difference between the tunnel and probe inlet static pressures was 

±0.035 psi (preset in the software). When the suction fan was switched off, the probe inlet static 

pressure returned rapidly to the initial state where a ramp pressure had been present. These 

characteristic static pressure distributions recorded during the tunnel operation (figure 4-23) were 

similar to those recorded during the static spray tests presented in figure 4-24, except that the 

ramp pressure was no longer present (in the spray tests). Therefore, the iso-kinetic performance 

of the probe in a laboratory was similar to that in the wind tunnel. 

In summary, although iso-kinetic flows were attained quite rapidly, water collection efficiencies 

were quite poor due to the extreme conditions in the WSU wind tunnel (RH ~ 20% to 40%, 

temperatures ~ 100o

F). It was believed that had the tests been conducted at conditions similar to 

those found in icing wind tunnels (RH ~ 90% to 100%, temperatures ~ 32oF), significant 

improvements would have been obtained. However, the addition of the humidity sensor inside 

the reference probe revealed the effect of evaporation on collection water efficiency and 

provided a new way for accounting for these effects. The use of a humidity sensor to correct for 

the effects of water evaporation inside the probe is discussed in section 5. 

4-15
Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 2

Run duration = 130 s

Probe inlet static press. = 0.2 psig

LWC (approx.) = 1.25 g/m3

TWC probe

Wind Tunnel (simulated)

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 18

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 1.22 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Suction Off

Line indicates Suction On

FIGURE 4-23. PROBE AND TUNNEL 

PRESSURE DISTRIBUTION—WIND 

TUNNEL IN OPERATION 

FIGURE 4-24. PROBE AND TUNNEL 

PRESSURE DISTRIBUTION—STATIC 

SPRAY TEST 

4-16
5. EXPERIMENTAL INVESTIGATION WITH THE WATER COLLECTOR 

CONFIGURATION 11 MOD-II DESIGN.

The water collector configuration 11 Mod-I was successfully tested under laboratory 

conditions. This design used a combination of blotter paper, silica gel, and B-Gon fiber to 

adsorb and trap incoming water droplets. However, the tests (collection efficiencies) conducted 

in the wind tunnel were less successful due to the dry conditions in the test section that led to 

excessive evaporation. Humidity sensors that were installed inside the probe and wind tunnel 

had recorded temperatures of around 100o

F and humidity below 35%. It must be recognized that 

the reference probe (final production version) is expected to perform at near-freezing conditions 

and humidity of about 100%; therefore, the test conditions in the WSU wind tunnel were far 

from ideal. In addition, silica gel desiccant (encased in the B-Gon mesh) also adsorbed moisture 

from the test environment as well as those evaporated by the water droplets from the spray cloud. 

Although they made significant contributions to the water collection efficiency measurements (as 

shown in figure 3-21), it was difficult to quantify their respective contributions due to the 

presence of the desiccant material, which affected the RH measurements. To overcome this 

problem, the desiccant was removed from the Mod-I design, and the hydrophobic B-Gon layer 

mesh was increased from two to six layers to prevent trapped water (in between the mesh) from 

escaping through the collector exit. The low-accuracy humidity sensor inside the reference 

probe was also replaced with a more accurate sensor, as shown in figure 5-1. This modified 

setup was renamed as configuration 11 Mod-II design since the only difference to the Mod-I 

design was the absence of the silica gel desiccant. A technique for computing the LWC values, 

water mass from the spray cloud, and environmental moisture was also devised using data 

recorded by the humidity sensor. 

A limited number of tests were performed in a laboratory with the Mod-II design due to the time 

constraint. This section describes the method of computing the LWC, test measurement, data 

reduction technique, and the results obtained. 

5.1 METHOD OF COMPUTING LWC WITH RELATIVE HUMIDITY MEASUREMENTS.

The proposed methodology relies on the measured data from the dry (spray-off) and wet (sprayon) tests, which would have been conducted consecutively under similar conditions, i.e., same 

probe inlet velocities and test conditions. The RH measurements recorded at the water collector 

exit (inside the probe) consisted of vapor from the test environment and evaporated moisture 

from the spray cloud. These measurements were converted to the absolute values by employing 

a set of humidity equations given in appendix F. In a dry (spray-off) test, the absolute vapor 

mass (Mv|dry) from the test environment alone was computed as follows: 

Mv|dry = RHsp|dry × Mh|dry (5-1) 

Similarly for a wet (spray-on) test, i.e., vapor attributed to the evaporated droplets and test 

environment 

Mv|wet = RHsp|wet × Mh|wet (5-2) 

5-1
where 

RHsp = specific humidity (ratio of the mass of water vapor (g) to the mass of humid air (g)) 

Mh = mass of humid air (air from the test environmental air) 

By performing the dry and wet tests consecutively, the errors due to changes in the 

environmental RH, temperature, and pressure as well as water lost due to evaporation inside 

the probe were minimized. (The test conditions must be similar, i.e., same probe inlet static 

pressures and test durations). The evaporated water droplets due only to the spray cloud 

(Mevp) were obtained by subtracting the above water vapor masses in equations 5-1 and 5-2 

as follow: 

Mevp = Mv|wet - Mv|dry (5-3) 

The total mass of the evaporated water, water adsorbed by the blotter paper (Mblotter) and BGon fiber (MB-Gon), must be equal to the amount of water that was sprayed into the reference 

probe, assuming no losses. Hence, 

Msprayed = Mevp + Mblotter + MB-Gon (assumes no losses) 

Therefore, the LWC value was computed as follows: 

( )

}{ h|dry h|wet

evp blotter B-Gon

or M M

 M MM

LWC

+ + =

since Mh|dry = Mh|wet, assuming that the dry and wet tests were performed under the same 

conditions. 

5.2 TEST MEASUREMENTS.

The ISFC system (section 4.3) was set up in the WSU laboratory where the initial tests to 

select an efficient water collector configuration was conducted (section 3). The Fisherbrand 

Traceable humidity probe that was installed in the reference probe was replaced with a 

Vaisala humidity sensor (figure 5-1), which is considerably more accurate. The Fisherbrand 

probe (figure 5-2) was used to record the environmental RH and temperature in the icing 

laboratory. To minimize the effects due to reingestion of the evaporated vapor, the exhaust 

air from the throttle valve was extracted from the laboratory by placing the throttle valve 

inside a fume cupboard, as shown figure 5-3. Figure 5-4 shows the instrumentations of the 

ISFC system including the DAQ system and DPI-601, which was used to provide a 

simulated tunnel static pressure. 

5-2
 

Fisherbrand 

humidity 

sensor 

Vaisala 

humidity 

sensor

Probe outlet 

FIGURE 5-1. HUMIDITY SENSOR INSIDE 

THE REFERENCE PROBE 

FIGURE 5-2. FISHERBRAND HUMIDITY 

SENSOR 

 

Throttle valve 

FIGURE 5-3. THROTTLE VALVE 

INSTALLED IN A FUME CUPBOARD 

FIGURE 5-4. ISO-KINETIC FLOW 

CONTROL SYSTEM 

The test procedures, described in appendix C, section C.1, were applied to the two 

consecutive tests (i.e., dry and wet tests). As mentioned earlier, probe inlet conditions for 

the wet and dry tests should be identical. However, in practice, inlet conditions can change 

to some extent when test durations are excessively long. To minimize this effect, the test (or 

run) durations were set to between 5 and 10 minutes. It was anticipated that the blotter 

paper would have to adsorb more water due to the longer test durations (compared to the test 

durations conducted previously in sections 3 and 4); therefore, a multilayered blotter paper 

tube was fabricated instead of the single-layered design used in previous tests. Figure 5-5 

shows the method of fabricating a multilayered blotter tube design. The two-layered B-Gon 

fiber mesh was replaced with a six-layered mesh to prevent trapped water (in between the 

mesh) from escaping through the collector exit. It was found that the aerodynamic 

performance (inlet suction) of the probe with this thicker mesh was unaffected, which seems 

to suggest that the pressure loss in the fiber mesh was similar to that caused by the silica gel. 

5-3
FIGURE 5-5. METHOD OF CREATING A MULTILAYERED BLOTTER TUBE

The results are shown in figures 5-6 to 5-9 and table 5-1; tests 1 to 4 were conducted with a 

probe inlet pressure of 0.9 psig, whereas tests 5 to 9 were conducted with 0.4 psig. The run 

duration in tests 8 and 9 were longer than the spray duration (i.e., the test run time was longer 

than the spray time). The graphical plots of the static pressure, relative humidity, and 

temperature for the tests, listed in table 5-1, are shown in appendix E. Due to time constraints, 

only a limited number of tests were performed. The following test conditions were used: 

• Water used or sprayed 3.05 to 19.8 g 

• Spray brush pressure setting 30 psig 

• Spray duration 300 to 600 s 

• Spray rate 0.009 to 0.066 g/s 

• LWC 0.24 to 2.56 g/m3

• Run duration 300 to 420 s 

0 0.5 1 1.5 2 2.5

LWC based on water collected (g/m3)

3

0

0.5

1

1.5

2

2.5

3

LWC based on water sprayed (g/m3)

Configuration no.11 Mod-II

Plastic container installed

B-Gon mesh

Blotter tube (100mm) on divergent exit

Test #7

Test #9

Line of symmetry

0 0.5 1 1.5 2 2.5

LWC based on water collected (g/m3)

3

0.2

0.4

0.6

0.8

1

1.2

1.4

Collection efficiency (%)Configuration no.11 Mod-II

Plastic container installed

B-Gon mesh 

Blotter tube (100m) on divergent exit

Test #7

Test #9

Collection efficiency curve-fit

(config#11 Mod-I)

Collection efficiency curve-fit

(config#11 Mod-II )

FIGURE 5-6. COMPARISON BETWEEN 

LWCs BASED ON WATER COLLECTED 

AND WATER SPRAYED 

FIGURE 5-7. LIQUID WATER CONTENT 

BASED ON WATER COLLECTED VERSUS 

COLLECTION EFFICIENCY 

5-4
0 0.5 1 1.5 2 2.5

LWC based on wate

3

r collected (g/m3)

0

0.2

0.4

0.6

0.8

1

1.2

LWC contrib.by blotter,B-Gon,evap.water (%)

Configuration no.11 Mod-II

Plastic container installed

B-Gon mesh

Blotter tube (100m) on divergent exit

Blotter paper

Evap. water

B-Gon

Test #7

Contrib. by blotter paper

(config#11 Mod-I)

Contrib. by B-Gon + silica gel

(config#11 Mod-I)

Test #9

Test #7

Test #9

0 0.5 1 1.5 2 2.5

LWC based on water collected (g

3

/m3)

0.95

0.975

1

1.025

1.05

Ratio of Wet to Dry Probe Volumetric flow 

Configuration no.11 Mod-II

Plastic container installed

B-Gon mesh

Blotter tube (100mm) on divergent exit 

Line indicates ratio of 1.0125

Line indicates ratio of 0.9875 Test #7

Test #9

FIGURE 5-8. CONTRIBUTION TO THE 

LWC BY BLOTTER, B-GON, AND 

EVAPORATED WATER 

FIGURE 5-9. DISTRIBUTION OF PROBE 

VOLUMETRIC MASS FLOW RATIO 

5-5
TABLE 5-1. TEST RESULTS FOR CONFIGURATION 11 MOD-II (LABORATORY) 

Row 1: Weight of 

Blotter Paper 

Row 2: Weight of 

B-Gon 

Weight of 

Spray Water 

Used 

Test 

No. Before After 

Total 

Amount 

of Water 

Collected 

(g) Before After 

Total 

amount 

of 

Water 

Used

(g) 

Probe 

Inlet 

Pres.

(psig)

Spray 

Pres.

(psig)

Water 

Spray 

Duration

(s) 

Run 

Duration 

(s) 

Rate 

of 

Spray

(g/s) 

Collection Efficiency 

(B-Gon)

(%) 

Collection Efficiency 

(Blotter)

(%) 

Loss 

Due to 

Evap.

(g) 

LWC 

(Based on 

Water 

Used) 

(g/m3) 

LWC 

(Based on 

Water 

Collected)

(g/m3) 

1 28.7339 30.0283 1.2971 108.5984 103.0045 5.5939 0.9 30 600.0 600.0 0.009 0.05 23.1 (4.2968) 0.2442 0.0566 

22.6448 22.6475 0.0027 

2 28.6090 29.3813 0.7727 111.6938 108.6464 3.0474 0.9 30 300.0 300.0 0.010 0.01 25.3 (2.2747) 0.2661 0.0675 

22.6475 22.6479 0.0004 

3 28.6767 34.4202 5.8437 107.7081 96.2707 11.4374 0.9 30 300.0 300.0 0.038 0.12 50.2 (5.5937) 0.9986 0.5102 

22.6443 22.6577 0.0134 

4 42.208 53.8775 11.6867 115.4514 97.6659 17.7855 0.9 30 300.0 300.0 0.059 -0.01 65.6 (6.0988) 1.5528 1.0204 

22.609 22.6072 -0.0018 

5 28.6567 35.5926 7.1473 126.6400 114.9471 11.6929 0.4 30 300.0 300.0 0.039 0.51 59.3 (4.5456) 1.5313 0.9360 

22.6370 22.6972 0.0602 

6 28.6554 35.1798 6.7514 96.2394 84.0242 12.2152 0.4 30 300.0 300.0 0.041 1.15 53.4 (5.4638) 1.5997 0.8842 

22.6403 22.7805 0.1402 

7 42.2233 54.9578 12.8272 96.2190 78.6219 17.5971 0.4 30 300.0 300.0 0.059 0.12 72.4 (4.7699) 2.3046 1.6799 

22.6356 22.6561 0.0205 

8 41.4475 51.8481 10.4641 94.9912 78.9244 16.0668 0.4 30 300.0 360.0 0.054 0.13 64.7 (5.6027) 2.1042 1.3704 

22.6331 22.6546 0.0215 

9 42.3359 55.5723 13.2735 111.6247 91.7976 19.8271 0.4 30 300.0 420.0 0.066 0.05 66.8 (6.5536) 2.5648 1.7170 

20.9647 20.9755 0.0108 

5-6
TABLE 5-1. TEST RESULTS FOR CONFIGURATION 11 MOD-II (LABORATORY) (Continued)

Dry Test Wetted Test 

Test 

No. 

Integrated 

Run 

Duration 

(s) 

Integrated 

Air Mass 

Flow 

(kg) 

Integrated 

Vapor 

Mass 

(g) 

Actual 

Amount of 

Water Used

(g) 

Total Vapor 

and Water 

Used 

(g) 

Integrated 

Run 

Duration

(s) 

Integrated 

Air Mass 

Flow 

(kg) 

Integrated 

Vapor Mass

(g) 

Amount of 

Water 

Collected by 

Blotter 

(g) 

Total 

Vapor and 

Water 

Collected

(g) 

1 598.4 24.826 233.876 5.5939 239.470 599.0 24.891 237.828 1.2971 239.125 2 298.7 12.297 114.327 3.0474 117.374 298.6 12.371 116.726 0.7727 117.499 3 297.7 12.325 114.840 11.4374 126.278 297.5 12.385 119.751 5.8437 125.595 4 297.71 12.24698 114.22327 17.7855 132.009 297.70 12.276 119.356 11.6867 131.043 5 299.0 8.294 80.389 11.6929 92.082 299.3 8.313 84.515 7.1473 91.662 6 300.0 8.396 80.974 12.2152 93.190 300.0 8.385 85.085 6.7514 91.836 7 300.0 8.376 81.116 17.5971 98.713 300.2 8.231 83.965 12.8272 96.792 8 358.3 9.888 96.730 16.0668 112.797 358.7 9.969 101.811 10.4641 112.275 9 419.9 11.927 115.477 19.8271 135.304 419.4 11.471 116.703 13.2735 129.976 

5-7
TABLE 5-1. TEST RESULTS FOR CONFIGURATION 11 MOD-II (LABORATORY) (Continued)

Computed 

Amount of 

Water 

Collected 

(g) 

Ratio 

Between 

Wetted and 

Dry Air 

Mass Flow 

Ratio Between 

Wetted and 

Dry Total 

Vapor and 

Water Mass 

(Collection Efficiency) 

Ratio Between 

Water Collected 

and Sprayed 

(%) 

LWC 

(Based on 

Computed 

Amount of 

Water Collected)

(g/m3) 

LWC 

(Based on 

Actual 

Amount of 

Water Sprayed)

(g/m3) 

Percent 

Difference 

LWC 

LWC 

Collection 

Contributed 

by B-Gon

(%) 

LWC 

Collection 

Contributed 

by Blotter 

(%) 

LWC 

Collection 

Contributed 

by Humidity

(%) 

5.248 1.003 0.999 93.82% 0.211 0.225 -6.18 23 0 71 3.172 1.006 1.001 104.07% 0.256 0.246 4.07 25 0 79 

10.755 1.005 0.995 94.03% 0.868 0.924 -5.97 51 0 43 16.820 1.002 0.993 94.57% 1.370 1.449 -5.43 66 0 29 11.273 1.002 0.995 96.41% 1.356 1.407 -3.59 61 1 35 10.862 0.999 0.985 88.92% 1.295 1.457 -11.08 55 1 34 15.676 0.983 0.981 89.08% 1.904 2.138 -10.92 73 0 16 15.545 1.008 0.995 96.75% 1.559 1.612 -3.25 65 0 32 14.499 0.962 0.961 73.13% 1.264 1.728 -26.87 67 0 6 

5-8
5.3 DATA REDUCTION.

The water vapor mass (from the dry and wet tests) was computed from the data recorded by 

the ISFC software (section 4.3). Typical measurements are shown in figures 5-10 to 5-12. 

These measurements contained time traces of the probe inlet static pressure, RH, and 

temperature measurements. The specific humidity (RHsp) in equations 5-1 and 5-2, section 

5.1, was computed by integrating the probe’s humidity distribution over the test duration for 

the dry and wet tests, respectively, as shown in figure 5-10. The start and end points of the 

integral represents the duration in which iso-kinetic condition was established in the probe 

(indicated by the overlap of the static pressure curves shown in figure 5-13). In a wet test, 

water would have been injected into the probe during this time, hence, RH inside the probe 

would also increase accordingly. The humid air mass (Mh) in equations 5-1 and 5-2, section 

5.1, was computed using the method described in section 3.5, in conjunction with the static 

pressure and temperature traces shown in figures 5-11 and 5-12, respectively. An equal 

amount of humid air should enter into the probe during the dry and wet tests if the probe 

operation and test conditions (in both tests) had been identical, i.e., equal suction pressures, 

temperature, and RH. However, in practice, there will always be a small difference due to 

local variations in the laboratory. The data reduction technique for computing LWC was 

based on the humidity formulations (equations F-1 to F-6) given in appendix F, hence, for a 

dry test, the steps involved are defined as follow: 

1. Compute the saturated vapor pressure (Esat) using the temperature traces 

(figure 5-12). 

2. Compute the vapor pressure (Ev) in equation F-1, appendix F, using the relative 

humidity traces (figure 5-10). 

3. Compute the mixing ratio (W) in equation F-2, appendix F, using the ambient 

pressure (assumed as 100 kPa) and vapor pressure from step 2. 

4. Compute the specific humidity (RHsp) in equation F-3, appendix F, using the mixing 

ratio from step 3. 

5. Compute the probe inlet velocity and air density (assumed ideal state) using the 

pressure (figure 5-6) and temperature (figure 5-11) trace curves, and then compute 

the mass of humid air (Mh) using equation F-4. 

6. Compute the mass of water vapor (Mv) in equation F-8, appendix F, i.e., multiply the 

mass of humid air (step 5) by the specific humidity value (step 4). 

7. Repeat steps 1 to 6 for each time step of the integration period (figure 5-10). This 

will generate a distribution curve of the water vapor mass versus time. 

8. Compute the total water vapor mass (Mv|dry, equation 5-1, section 5.1) by integrating 

the distribution curve generated in step 7 for the test duration, i.e., between the start 

and end points of the integration period. 

9. Repeat steps 1 to 8 to obtain the total vapor mass (Mv|wet, equation 5-2 in section 5.1) 

for the wet test. 

5-9
10. Compute the mass of the evaporated water droplets from the spray cloud (Mevp) only, 

i.e., Mevp = Mv|wet - Mv|dry.

11. Compute the LWC using the mass of water collected by the blotter paper (Mblotter)

and B-Gon mesh (MB-Gon), i.e., 

( )

}{ h|dry h|wet

evp blotter B-Gon

or M M

 M MM

LWC

+ + =

0 100 200 300 400 500

Time (s)

46

48

50

52

54

56

58

60

62

Relative humidity (%)

 Test number 3

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.99 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Line indicates 

Suction Off

Line indicates 

Suction On

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates Suction Off

Line indicates Suction On

0 100 200 300 400 500

Time (s)

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 3

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.99 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Curves used for computing 

specific humidity

Integration 

period 

Iso-kinetic 

condition 

Start point End point 

Curves used for 

computing probe 

inlet velocity and 

density 

FIGURE 5-10. PROBE RH DISTRIBUTION FIGURE 5-11. PROBE STATIC 

PRESSURE DISTRIBUTION 

0 100 200 300 400 500

Time (s)

21.5

22

22.5

23

23.5

24

24.5

25

25.5

Temperature (

oC)

 Test number 3

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.99 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates

Suction Off

Line indicates 

Suction On

Curves used for 

computing density 

FIGURE 5-12. PROBE TEMPERATURE DISTRIBUTION

5-10
5.4 RESULTS AND DISCUSSION.

Figure 5-9 shows that the amount of water collected for all the test data, except for tests 7 and 9, 

was almost equal to the amount sprayed into the reference probe and their collection efficiencies 

were within 95%, as shown in figure 5-7. The collection efficiencies for all the data varied from 

73% to 104%. The amount of water collected in tests 7 and 9 was less than the amount sprayed. 

(The cause of the poor measurements is the unequal volumetric mass flow in tests 7 and 9, which 

will be explained later in this section.) The curve fitted to the collection efficiency obtained 

from configuration 11 Mod-I (section 3) is included in figure 5-10 for comparison. The results 

show that both curves exhibited similar trends, but the overall collection efficiency obtained with 

the Mod-II collector was slightly lower than the Mod-I results. The mean collection efficiency 

and standard deviation (table 5-1) for the Mod-II collector were 92.1% and 8.28%, respectively, 

compared to 100.8% and 7.89%, respectively, for the Mod-I design. It must be noted that the 

statistical calculation used in the Mod-I analysis involved 65 data points, whereas only 9 data 

points were used here. 

The contributions to the LWC (based on water collected) by the blotter paper, B-Gon fiber mesh, 

and evaporated water calculated from the humidity data are shown in figure 5-8. The fitted 

curves from the Mod-I collector were also included in this figure for comparison. The results 

(figure 5-8) show that the contributions by the blotter paper remained unchanged, whereas 

negligible contributions by the B-Gon mesh were found. The results also show that the 

contributions by the evaporated water seem to have replaced the contributions made by the silica 

gel desiccants in the Mod-I design. The effect of using a three-layered blotter paper instead of a 

single layer was negligible. The effect of extending the test duration after water spray was 

stopped (in tests 8 and 9 shown in figures D-8 and D-9 in appendix D) was difficult to 

characterize due to insufficient test data. It was clear that the computed evaporated water mass 

from test 9 was quite low. 

Figure 5-9 shows the distribution of the volumetric mass flow ratio (between the wet and dry 

tests) plotted against the LWC (based on water collected). The volumetric mass flow represents 

the total amount of environmental air that entered the reference probe within a certain duration, 

e.g., a ratio of unity implied that equal volumetric mass flow for the wet and dry tests. The 

results show that in all cases except for tests 7 and 9, the ratio of volumetric flow for the dry and 

wet tests was between 0.9875 and 1.0125 (indicated by the dotted lines). The ratios obtained for 

tests 7 and 9 were less than 0.9875, and the corresponding probe collection efficiencies were 

89.1% and 73.1%, respectively. It was noticed that when the ratios of the volumetric mass flow 

laid between the limiting values 0.9875 and 1.0125, the collection efficiencies would lie near the 

maximum value of 100%. This characteristic trend could be used in the future to determine the 

quality of the measurements. The reasons for the low volumetric mass ratios in tests 7 and 9 can 

be explained by studying the distributions of probe inlet static pressure in appendix E. Two test 

cases were selected: test 2 in figure 5-13 and test 7 in figure 5-14. For the cases where the ratios 

were between the limits of 0.9875 and 1.0125, the pressure distributions measured in the spray 

and dry tests were similar and characterized by coincident curves, as shown in figure 5-13. 

However, in tests 7 and 9, where the ratios laid below 0.9875, the pressure distribution curves 

were not coincident. This implied unequal volumetric mass flows in the spray and dry tests for 

tests 7 and 9, hence, did not satisfy the required conditions for calculating the evaporated water 

droplets, as described in section 5.1 (highlighted in italics). The probe inlet static pressure 

5-11
distributions for all other tests presented in appendix E exhibited coincidence curves, hence, 

higher collection efficiencies. 

Line indicates Suction Off

Line indicates Suction On

0 100 200 300 400 500

Time (s)

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 2

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.27 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

0 100 200 300 400 500

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 7

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.68 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Line indicates Suction Off

Line indicates Suction On

FIGURE 5-13. STATIC PRESSURE 

DISTRIBUTION—TEST 2 

FIGURE 5-14. STATIC PRESSURE 

DISTRIBUTION—TEST 7 

In conclusion, a new technique of calculating the LWC with humidity measurements has 

been developed. This technique could be implemented to develop an accurate LWC 

instrument for warm cloud conditions. 

5-12
6. SUMMARY. 

This section gives a summary of the work tasks that led to the successful development of the 

conceptual probe, and they are described as follows. 

• A conceptual probe was designed and fabricated by the Icing Group in the Department of 

Aerospace Engineering at Wichita State University. This probe was used to demonstrate 

the concept of applying iso-kinetic flow to the measurement of the LWC for spray clouds 

with small and large water droplets. 

• The probe consisted of a 90 degree elbow tube and a water collector assembly that was 

attached to an enclosed chamber with a single exit nozzle that was connected to a suction 

fan. The material used in the construction included Ultra-High-Molecular Weight 

Polyethylene, Perspex, and stainless steel wire mesh. 

• Computer fluid dynamics analyses simulating the probe internal flow and the external 

flow about the probe installed in a wind tunnel were performed to support the initial 

design process. 

• Significant effort was directed at the development of an efficient water collector and 

calibration of the collector water catch efficiency in a laboratory and wind tunnel. A total 

of 11 different configurations of the water collector, involving a range of different wateradsorbent materials, were tested in a laboratory. 

• The collector design with the highest collection efficiency was selected for further 

testing. This design, which was named configuration 11 Mod-I (C11 Mod-I), consisted 

of an enclosed chamber with a central exit hole and contained silica gel desiccant, blotter 

paper, and B-Gon fiber mesh. 

• Calibration tests were conducted in a laboratory to ascertain the measurement accuracy of 

the C11 Mod-I collector. This involved injecting a known amount of water droplets into 

the probe and comparing this to the amount adsorbed by the water collector. The LWC 

was determined from the amount of water used (or collected) and the volumetric air 

drawn by the probe. 

• Limited tests were conducted at the WSU 7- by 10-ft tunnel to check the iso-kinetic 

performance of the probe. Prior to the wind tunnel tests, a LabView computer program 

that could maintain iso-kinetic flow condition at the probe inlet was developed and tested 

in a laboratory. 

• During the wind tunnel experiments, humidity sensors were installed inside the probe and 

in the wind tunnel to monitor the humidity level inside the probe and in the free stream. 

Extremely high temperatures and low relative humidity levels were recorded. 

• The installation of a humidity sensor inside the probe led to an improved technique of 

measuring the LWC. Limited tests were conducted in a laboratory to determine the 

6-1
amount of water evaporated inside the probe and this measurement was used to correct 

the calculation of the LWC. With the inclusion of the humidity sensor in the probe and 

water collector, C11 Mod-I was renamed C11 Mod-II. 

• The preliminary experimental tests used to develop an efficient water collector 

configuration resulted in two successful designs. 

− Configuration 11 Mod-I consists of an enclosed chamber with a central exit 

nozzle, cylindrical tube fabricated from blotter paper, B-Gon hydrophobic fiber 

mesh, and silica gel desiccant. 

− Configuration 11 Mod-II consists of an enclosed chamber with a central exit 

nozzle, cylindrical tube fabricated from blotter paper, B-Gon hydrophobic fiber 

mesh, and relative humidity sensor. 

6-2
7. CONCLUSIONS.

The following conclusions were drawn from the work conducted. 

• The water collector configuration (C11 Mod-I) consisting of an enclosed chamber with a 

central exit tube, blotter paper, and hydrophobic fiber mesh exhibited the highest water 

collection efficiencies. The mean and standard deviation of the collection efficiency 

were 100.8% and ±7.89%, respectively. These were determined in a laboratory for liquid 

water content (LWC) values in the range of 0.54 and 8.5 g/m3

. 

• The mass of water collected by the blotter paper increased with increasing LWC, whereas 

water collected by the silica gel and B-Gon material decreased. The water collected by 

the silica gel, B-Gon, and blotter paper materials was almost equal to the water sprayed 

into the probe. The amount of water sprayed (or used) in the laboratory tests varied from 

2.26 to 10.5 g, and the spray durations were between 30 and 130 seconds. 

• The collection efficiencies obtained with the C11 Mod-I design in the Wichita State 

University (WSU) wind tunnel were quite low because of the high temperature and very 

low humidity conditions in the tunnel air stream, which led to excessive evaporation of 

the water droplets from the spray cloud. 

• The probe was tested in the WSU wind tunnel at velocities between 105 and 130 mph (or 

47 and 58 m/s). Although the probe inlet velocity was capable of operating at velocities 

up to 220 mph (~100 m/s), the selected airspeeds for the tests were lower to reduce the 

loads on the probe and mounting system. It was thought that the probe, which was 

fabricated from Ultra-High-Molecular Weight Polyethylene and Perspex materials, might 

not have adequate structural integrity to withstand the forces at higher tunnel velocities. 

• The iso-kinetic flow control system was able to maintain iso-kinetic conditions at the 

probe inlet during the experimental tests in the WSU wind tunnel. Iso-kinetic condition 

at the probe inlet was attained within 3 seconds of operating the probe suction system. 

• The removal of silica gel desiccant and the addition of an accurate humidity sensor to 

configuration 11 led to the development of an improved LWC reference probe design. 

This modified configuration was named configuration 11 Mod-II (C11 Mod-II). The 

mean and standard deviation of the water collection efficiency (based on limited test 

data) were 92.1% and ±8.28%, respectively. These were determined in a laboratory with 

water sprays having LWC in the range of 0.24 and 2.56/m3

. The amount of water used 

during the test sprays varied from 3.05 to 19.8 g, and the spray durations were in the 

range of 5 to 10 minutes. The C11 Mod-II design was not tested in the wind tunnel due 

to time and cost constraints. 

7-1/7-2
8. RECOMMENDATIONS. 

The end of the development phase produced two methods of water collection that could 

potentially be turned into an accurate instrument for measuring LWC under supercooled droplets 

conditions. Both the C11 Mod-I and C11 Mod-II collector designs were successfully 

demonstrated under laboratory conditions. The iso-kinetic performance of the probe was also 

successfully demonstrated in a wind tunnel at velocities up to 130 mph. There is a need for 

further experimentations to fully develop the iso-kinetic probe for an icing wind tunnel. This can 

be carried out in three phases: Phase 2 compares the LWC measured by the reference probe and 

an existing LWC instrument in a wind tunnel, Phase 3 involves fabricating a new airfoil-shaped 

reference probe suitable for a wind tunnel, and Phase 4 assesses the probe’s performance in an 

icing wind tunnel. 

8-1/8-2
9. REFERENCES. 

1. Ide, R.F., “Comparison of Liquid Water Content Measurement Techniques in an Icing 

Wind Tunnel,” NASA TM-1999-209643, 1999. 

2. Rudoff, R.C., Bachalo, E.J., and Bachalo, W.D., “Liquid Water Content Measurement 

Using the Phase Doppler Particle Analyzer in the NASA Lewis Icing Research Tunnel,” 

AIAA 93-0298, Reno, NV, 1993. 

3. Tan, S.C. and Bartlett, P.G., “An Experimental Study of Droplet Break-Up Using a Wind 

Tunnel,” AIAA-2003-391, 2003. 

4. Mundo, Chr, Sommerfeld, M., and Tropea, C., “Droplet-Wall Collisions: Experimental 

Studies of the Deformation and Breakup Process,” Int. J. Multiphase Flow, Vol. 21, 

No. 2, 1995, pp. 151-173. 

5. Cohen, J.M. and Rosfjord, T.J., “ Spray Patternation at High Pressure,” AIAA-89-2323, 

Monterey, CA, 1989. 

6. Papadakis, M., Hung, K.E, and Yeong, H.W., “Experimental Investigation of Water 

Impingement on Single and Multi-Element Airfoils,” AIAA-2000-0100, 2000. 

7. Von Glahn, U., Gelder, T.F., and Symers, W.H. Jr., “ A Dye Tracer Technique for 

Experimentally Obtaining Impingement Characteristics of Arbitrary Bodies and a 

Method for Determining Droplet Size Distribution,” NACA TN3338, March 1955. 

9-1/9-2
APPENDIX A—CHARACTERISTICS OF SILICA GEL AND 

MOLECULAR SIEVE DESICCANTS 

0 20 40 60 80 1

Relative Humidit

00

y (%)

0

10

20

30

40

H20 capacity at 77°F(25°C)gm H2O/100 gm adsorbent

Molecular sieve

Silica gel

FIGURE A-1. VARIATION OF DESICCANT ADSORPTIVE 

CAPACITY WITH RELATIVE HUMIDITY 

0 100 200 300 400 500 600

Temperature (oF)

0

5

10

15

20

25

30

Equilibrium Capacitygm H2O/100 gm adsorbent

Molecular sieve

Silica gel

FIGURE A-2. VARIATION OF DESICCANT ADSORPTIVE 

CAPACITY WITH TEMPERATURE 

A-1/A-2
APPENDIX B—WATER COLLECTOR CONFIGURATION TESTS

The following describes the configurations of the water collector including their results and 

findings using the definitions for the collection efficiency and rate of spray given in section 3.3. 

B.1 CONFIGURATION 1. 

B.1.1 Description. 

B-Gon fiber was wrapped around the sidewalls of the container, whereas the base (of the 

container) was wrapped with water-adsorbent paper over the B-Gon fiber. Both the B-Gon fiber 

and adsorbent paper were secured with elastic bands. A centrifuge was also installed at the base 

of the divergent nozzle of the probe top section. It was anticipated that water would be trapped 

in the fiber while the (adsorbent) paper would adsorb water. Figures B-1a and B-1b show the 

components of the water collector before and after assembly. The test conditions and 

configuration of the water collector are defined as follows: 

• Water collection medium B-Gon fiber mesh, water-adsorbent paper 

• Weighed components Inner container, B-Gon, water-adsorbent paper 

• Features Centrifuge installed 

• Water used or sprayed 2.5 to 14.0 g 

• Spray brush pressure setting 20, 30 psig 

• Spray duration 15 to 60 s 

• Spray rate 0.083 to 0.530 g/s 

• Run duration 20 to 60 s 

B.1.2 Findings. 

The results are shown in figure B-1c and table 3-1. Tests 1 to 4 were conducted at a spray 

pressure of 20 psig with a number of different spray and run durations. Tests 5 to 16 were 

conducted at a spray pressure of 30 psig with equal spray and run durations. 

Visual examination of the collector showed that the wetted regions were found on the B-Gon 

fiber but a small amount was also found on the base of the container. The collection efficiencies 

varied from 30% to 70%. Figure B-1c shows that collection efficiency increased with the rate of 

water sprayed. The total amount of water sprayed into the probe has minimal effect on the final 

collection efficiency. Extending the run durations (tests 1 to 4) after the water spray was stopped 

also has minimal effect. Tests conducted at lower spray pressures (tests 1 to 4) have higher 

collection than those conducted at higher pressures (tests 5 to 16). The droplet size generated by 

the spray brush depends on the spray rate and pressure; high water flow rates or low spray 

pressures usually produce large droplets, and vice-versa. Therefore, water collection efficiency 

tends to increase with droplet size. 

In summary, this configuration did not exhibit high collection efficiency, although measurements 

were repeatable. 

B-1
Centrifuge Inner 

container 

Water 

Adsorbent paper

Elastic 

bands 

B-Gon 

fiber mesh

FIGURE B-1a. CONFIGURATION 1 

(BEFORE ASSEMBLY) 

FIGURE B-1b. CONFIGURATION 1 

 (AFTER ASSEMBLY) 

0 0.2 0.4 0.6 0.8 1

Rate of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.1

Inner container installed

Centrifuge installed

B-Gon on walls 

Water adsorbent paper on base

Curve-fit

FIGURE B-1c. CONFIGURATION 1 

B-2
B.2 CONFIGURATION 2. 

B.2.1 Description. 

Water-adsorbent paper was wrapped around the sidewalls of the container and around the base of 

the container. The adsorbent papers were secured with elastic bands. A centrifuge was also 

installed at the base of the divergent nozzle of the top probe section. It was anticipated that 

(adsorbent) paper alone would collect all the water. Figures B-2a and B-2b show the 

components of the water collector before and after assembly. The test conditions and 

configuration of the water collector are defined as follows: 

• Water collection medium Water-adsorbent paper 

• Weighed components Inner container, water-adsorbent paper 

• Feature Centrifuge installed 

• Water used or sprayed 2.5 to 5.2 g 

• Spray brush pressure setting 30 psig 

• Spray duration 20 to 60 s 

• Spray rates 0.085 to 0.175 g/s 

• Run duration 20 to 60 s 

B.2.2 Findings. 

The results are shown in figure B-2c and table 3-2. Tests 1 to 14 were conducted with 

decreasing spray rates (i.e., decreasing volume mass), whereas tests 15 and 16 have two layers of 

water-adsorbent papers (all other tests had only one layer) but the spray duration in test 15 was 

twice as long as test 6. 

Visual examination of the collector showed that the wetted regions were found on the sidewalls 

and base of the container but a small amount was also found on the base. The collection 

efficiencies varied from 28% to 53%. Similar characteristics to the previous configuration were 

found for this configuration, i.e., collection efficiency increases with spray rate (figure B-2c), the 

total amount of water sprayed has minimal effect on the collection efficiency. In addition, 

adding an extra layer of water adsorbent or doubling the test durations did not improve upon the 

collection efficiency. 

In summary, this configuration performed slightly worse than the previous configuration. It also 

did not exhibit high collection efficiency although measurements were repeatable. 

B-3
Centrifuge Inner 

container 

Water adsorbent 

paper 

Elastic 

bands 

FIGURE B-2a. CONFIGURATION 2 

(BEFORE ASSEMBLY) 

FIGURE B-2b. CONFIGURATION 2 

(AFTER ASSEMBLY) 

0.04 0.08 0.12 0.16 0.2

Rate of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.2

Inner container installed

Centrifuge installed

Water adsorbent paper on walls

Water adsorbent paper on base

Curve-fit

FIGURE B-2c. CONFIGURATION 2 

B-4
B.3 CONFIGURATION 3. 

B.3.1 Description. 

This is a variant of configuration 2, except the centrifuge has been removed. Water-adsorbent 

papers were used to wrap the sidewalls and base of the inner container. The adsorbent papers 

were secured with elastic bands. Figures B-3a and B-3b show the components of the water 

collector before and after assembly. The test conditions and configuration of the water collector 

are defined as follows: 

• Water collection medium Water-adsorbent paper 

• Weighed components Inner container, water-adsorbent paper 

• Water used or sprayed 1.2 to 5.0 g 

• Spray brush pressure setting 30 psig 

• Spray duration 20 to 40 s 

• Spray rate 0.039 to 0.156 g/s 

• Run duration 20 to 40 s 

B.3.2 Findings. 

The results are shown in B3c and table 3-3. Tests 1 to 7 were conducted with a decreasing water 

spray rates (or decreasing volume mass). 

Visual examination of the collector showed that the wetted regions were found on the base of the 

container but a small amount was also found on the sidewalls. This (wetted) region was biased 

towards one corner of the base, which was similar to the computational fluid dynamics 

predictions in section 2.3.2. The collection efficiencies varied from 40% to 63%. The removal 

of the centrifuge enhanced the efficiencies slightly compared to configuration 2 without the 

centrifuge. However, they were similar to those measured with configuration 1 (for the same 

water spray rates). Similar characteristics to the previous configuration were found for this 

configuration, i.e., collection efficiency increases with spray rate (figure B-3c), the total amount 

of water sprayed has minimal effect on the collection efficiency. 

In summary, this configuration did not exhibit high collection efficiency, although measurements 

were repeatable. 

B-5
Inner 

container 

Water adsorbent 

paper 

FIGURE B-3a. CONFIGURATION 3 

(BEFORE ASSEMBLY) 

FIGURE B-3b. CONFIGURATION 3 

 (AFTER ASSEMBLY) 

0 0.04 0.08 0.12 0.16 0.

Rate

2

of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.3

Inner container installed

Water adsorbent paper on walls

Water adsorbent paper on base

Curve-fit

FIGURE B-3c. CONFIGURATION 3 

B-6
B.4 CONFIGURATION 4. 

B.4.1 Description. 

This is a variant of configuration 3 where an additional outer layer of water adsorbent paper was 

added in the form of an enclosed bag. This layer was attached using the outer container supports 

by removing the wire mesh. The bag was secured against the edge of the probe top section by 

the outer container supports and four elongated screws. Figures B-4a and B-4b show the 

components of the water collector before and after assembly. The test conditions and 

configuration of the water collector are defined as follows: 

• Water collection medium Water-adsorbent paper 

• Weighed components Inner container, water-adsorbent paper 

• Water used or sprayed 2.7 g 

• Spray brush pressure setting 30 psig 

• Spray duration 30 s 

• Spray rate 0.090 g/s 

• Run duration 30 s 

B.4.2 Findings. 

The results are shown in figure B-4c and table 3-4. Test 1 has one layer of adsorbent paper 

wrapped around the sidewalls of the inner container, whereas test 2 has three layers (wrapped 

around the inner container). 

Visual examination of the collector showed that the wetted regions were concentrated on the 

base of the container but a small amount was also found on the sidewalls. The (wetted) region 

was also biased towards one corner of the base. The collection efficiencies for tests 1 and 2 were 

55% and 49%, respectively. The addition of the extra adsorbent layer did not show significant 

improvement to the collection efficiency. 

B-7
Inner 

container 

Water adsorbent 

paper 

Outer container 

support 

Probe top 

section 

FIGURE B-4a. CONFIGURATION 4 

 (BEFORE ASSEMBLY) 

FIGURE B-4b. CONFIGURATION 4 

(AFTER ASSEMBLY) 

0.04 0.08 0.12 0.16 0.2

Rate of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.4

Inner container installed

Water adsorbent paper on walls

Water adsorbent paper on base

Water adsorbent paper on outer container

FIGURE B-4c. CONFIGURATION 4 

B-8
B.5 CONFIGURATION 5. 

B.5.1 Description. 

B-Gon fiber was wrapped around the sidewalls and base of the inner container. The fiber mesh 

was secured with elastic bands and held-in place by the outer container supports. It was 

anticipated that the B-Gon fiber would trap water between layers of the mesh. Figures B-5a and 

B-5b show the components of the water collector before and after assembly. The test conditions 

and configuration of the water collector are defined as follows: 

• Water collection medium B-Gon fiber mesh 

• Weighed components Inner container and B-Gon fiber mesh 

• Water used or sprayed 1.8 to 5.4 g 

• Spray brush pressure setting 30 psig 

• Spray duration 30 to 60 s 

• Spray rate 0.061 to 0.094 g/s 

• Run duration 30 to 60 s 

B.5.2 Findings. 

The results are shown in figure B-5c and table 3-5. Tests 1 to 14 were conducted at a spray 

pressure of 30 psig at similar water spray rates. 

Visual examination of the collector showed that the wetted regions were concentrated on the 

base of the container but a small amount was also found on the sidewalls. The collection 

efficiencies varied from 21% to 62%. Figure B-5c showed a scattered distribution of collection 

efficiencies that did not vary with either the spray rates or the amount of water spayed. 

In summary, the collection efficiencies were random, nonrepeatable, and did not exhibit high 

collection efficiency. 

B-9
Outer container supports 

Inner container 

Wire mesh to 

support base 

FIGURE B-5a. CONFIGURATION 5 

(BEFORE ASSEMBLY) 

FIGURE B-5b. CONFIGURATION 5 

(AFTER ASSEMBLY) 

0.04 0.08 0.12 0.16 0.2

Rate of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.5

Inner container installed

Outer container installed

B-Gon on walls

B-Gon on base

Curve-fit

FIGURE B-5c. CONFIGURATION 5 

B-10
B.6 CONFIGURATION 6. 

B.6.1 Description. 

A single Perspex tube (1-inch diameter) was fitted directly onto the 90 degree elbow tube and 

bypasses the divergent nozzle of the probe top section. The exit end of the Perspex tube was 

connected to a plastic container (diameter 4.8 inches, length 5.5 inches), which has a perforated 

top cover. It was anticipated that water droplets exiting from the tube would be adsorbed with a 

multilayered water-adsorbent material before being exhausted through the perforated cover of 

the plastic container. The adsorbent materials used were molecular sieve pellets that had been 

packed into 1-inch-square pouches fabricated from highly porous paper. Figures B-6a and B-6b 

show the components of the water collector before and after assembly. The test conditions and 

configuration of the water collector are defined as follows: 

• Water collection medium B-Gon fiber mesh, molecular sieve desiccant 

• Weighed components Plastic container, B-Gon, molecular sieve 

• Water used or sprayed 2.2 to 3.2 g 

• Spray brush pressure setting 30 psig 

• Spray duration 30 s 

• Spray rate 0.072 to 0.108 g/s 

• Run duration 30 s 

B.6.2 Findings. 

The results are shown in figure B-6c and table 3-6. Tests 1 to 4 were conducted at a spray 

pressure of 30 psig. 

Visual examination of the collector showed that some water had leaked through the top cover of 

the plastic container. The collection efficiencies varied from 54% to 68%. The collection 

efficiencies obtained from this configuration were slightly higher than previous configurations at 

similar spray rates. It was believed that this was probably due to the water adsorbed by the 

molecular sieve pellets (rather than the B-Gon fiber). There were insufficient data to ascertain 

the repeatability in the measurements but overall collection efficiencies were well below 100%. 

In summary, this configuration was not considered as an efficient water collector. 

B-11
90-degree 

elbow tube 

 

Central Perspex tube 

B-Gon 

fiber 

Plastic 

container 

Molecular sieve 

desiccant

Perforated cover 

FIGURE B-6a. CONFIGURATION 6 

(BEFORE ASSEMBLY) 

FIGURE B-6b. CONFIGURATION 6 

(AFTER ASSEMBLY) 

0 0.04 0.08 0.12 0.16 0.2

Rate of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.6

Inner container installed

Perspex tubing installed

B-Gon inside container

Molecular sieve inside container

Curve-fit

FIGURE B-6c. CONFIGURATION 6 

B-12
B.7 CONFIGURATION 7. 

B.7.1 Description. 

This is a variant of configuration 2, except the centrifuge has been replaced with special holder 

assembly that contained DRIMOP and molecular sieve pellets (packed into 1-inch-square 

pouches). The holder was installed at the base of the divergent nozzle of the probe top section. 

Water-adsorbent paper was wrapped around the sidewalls and base of the inner container. The 

adsorbent papers were secured with elastic bands. Based on the results from configuration 6, it 

was hoped that desiccants would improve collection efficiency. Figures B-7a and B-7b show the 

components of the water collector before and after assembly. The test conditions and 

configuration of the water collector are defined as follows: 

• Water collection medium DRIMOP, molecular sieve, water-adsorbent paper 

• Weighed components Inner container, water-adsorbent paper, DRIMOP, 

molecular sieve desiccant and holder assembly 

• Water used or sprayed 2.2 to 3.0 g 

• Spray brush pressure setting 30 psig 

• Spray duration 30 s 

• Spray rate 0.073 to 0.099 g/s 

• Run duration 30 s 

B.7.2 Findings. 

The results are shown in figure B-7c and table 3-7. Test 1 used both DRIMOP and molecular 

sieve, test 2 used molecular sieve, and tests 3 to 5 used DRIMOP as the main water-adsorbent 

material. 

Visual examination of the collector showed that the sidewalls and base of the inner container 

were quite dry. The collection efficiencies varied from 51% to 63%. These results were similar 

to that obtained from configuration 6. 

In summary, this configuration did not exhibit significant improvement in the collection 

efficiencies. 

B-13
DRIMOP installed 

in holder assembly 

Inner 

container Water adsorbent 

paper 

Molecular sieve 

FIGURE B-7a. CONFIGURATION 7 

(BEFORE ASSEMBLY) 

FIGURE B-7b. CONFIGURATION 7 

(AFTER ASSEMBLY) 

0 0.04 0.08 0.12 0.16 0.2

Rate of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.7

Inner container installed

Water adsorbent paper on base

and wall of inner container

Molecular sieve and DRIMOP on

divergent nozzle

Curve-fit

FIGURE B-7c. CONFIGURATION 7 

B-14
B.8 CONFIGURATION 8. 

B.8.1 Description. 

This is a variant of configuration 3, except for the addition of blotter paper, which was installed 

inside the hollow well of the inner container. The blotter paper was arranged in a gridlock 

formation with 1/2 inch spacing. It was anticipated that both the blotter and water-adsorbent 

papers would adsorb the water. The gridlock arrangement increases the surface area of the 

blotter paper. Water-adsorbent paper was wrapped around the sidewalls and base of the 

container. The adsorbent papers were secured with elastic bands. Figures B-8a and B-8b show 

the components of the water collector before and after assembly. The test conditions and 

configuration of the water collector are defined as follows: 

• Water collection medium Water-adsorbent paper, blotter paper 

• Weighed components Inner container, water-adsorbent paper, blotter paper 

• Water used or sprayed 2.6 to 3.6 g 

• Spray brush pressure setting 30 psig 

• Spray duration 30 s 

• Spray rate 0.087 to 0.120 g/s 

• Run duration 30 s 

B.8.2 Findings. 

The results are shown in figure B-8c and table 3-8. Tests 1 to 4 were conducted at a spray 

pressure of 30 psig. 

Visual examination of the collector showed significant water deposition on the blotter paper and 

on the base of the container. Certain regions of the sidewall were also wetted. The collection 

efficiencies varied from 50% to 68%. The results indicated that the collection efficiency were 

similar to those obtained from configuration 3 but no significant improvement was found. 

In summary, the addition of the blotter paper did not improve the collection efficiency. 

B-15
Water adsorbent 

paper 

Blotter 

paper 

Hollow 

well 

FIGURE B-8a. CONFIGURATION 8 

(BEFORE ASSEMBLY) 

FIGURE B-8b. CONFIGURATION 8 

(AFTER ASSEMBLY) 

0 0.04 0.08 0.12 0.16 0.2

Rate of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.8

Inner container installed

Water adsorbent paper on base

and walls of inner container

Blotter paper in gridlock arrangement

Curve-fit

FIGURE B-8c. CONFIGURATION 8 

B-16
B.9 CONFIGURATION 9. 

B.9.1 Description. 

This is a variant of configuration 8, except the blotter paper gridlock was replaced with a 

cylindrical tube that was also fabricated from blotter paper. This (tube) was attached to the base 

of the divergent nozzle (of the probe top section) and secured with a brass ring. The diameter of 

the cylindrical blotter tube was 3.0 inches, and the length was 3.94 inches (100 mm). An 

inverted plastic cup (2.5 inches diameter by 2 inches high) was also installed at the base of inner 

container. It was anticipated that the inverted cup would create partial blockage of the main 

airstream, thus diverting them towards the blotter tube where water droplets would be deposited. 

The base of the inverted cup was also installed with blotter paper. Water-adsorbent papers were 

used to wrap the sidewalls and base of the inner container. Figures B-9a and B-9b show the 

components of the water collector before and after assembly. The test conditions and 

configuration of the water collector are defined as follows: 

• Water collection medium Water-adsorbent paper, blotter paper 

• Weighed components Inner container, inverted cup, water-adsorbent paper, 

blotter paper 

• Water used or sprayed 1.6 to 2.7 g 

• Spray brush pressure setting 30 psig 

• Spray duration 30 s 

• Spray rate 0.053 to 0.091 g/s 

• Run duration 30 s 

B.9. 2 Findings. 

The results are shown in figure B-9c and table 3-9. Tests 1 to 18 were conducted at a spray 

pressure of 30 psig. 

Visual examinations showed significant water deposition on the blotter tube but none was found 

in the cup or on the inner container. The collection efficiencies varied from 62% to 77%. A 

significant improvement in the collection efficiencies was obtained with this configuration. It 

was believed that this (improvement) was attributed to the water adsorbed by the cylindrical 

blotter tube from the divergent nozzle section of the probe. 

In summary, the blotter tube design merited further investigations in the next configuration. 

B-17
Inverted cup

Cylindrical blotter tube 

Inverted cup 

Water adsorbent

paper 

FIGURE B-9a. CONFIGURATION 9 

(BEFORE ASSEMBLY) 

FIGURE B-9b. CONFIGURATION 9 

(AFTER ASSEMBLY) 

0.05 0.06 0.07 0.08 0.09 0.1

Rate of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.9

Inner container installed

Water adsorbent paper on base

and walls of inner container

Blotter paper tube on divergent nozzle

Curve-fit

FIGURE B-9c. CONFIGURATION 9 

B-18
B.10 CONFIGURATION 10. 

B.10.1 Description. 

This is a variant of configuration 9, except the inner container was replaced with a plastic 

container (diameter 4.8 inches by length 5.5 inches) with a bent central exit tube. It was 

anticipated that the plastic container would reduce evaporation of the cylindrical blotter tube. 

The central exit tube (of the plastic container) was bent because it was cut from a clear PVC 

elbow tube (diameter 1.5 inches, length 2 inches). A new 90 degree probe tube with four static 

pressure ports (figure 3-4) was installed into the probe top section to record the inlet pressure 

with a U-tube water manometer for the first time. Since the static pressures difference between 

the four ports were less than 0.036 psig (1′′H2O), it was decided to use only the bottom port for 

measurement. Figures B-10a and B-10b show the components of the water collector before and 

after assembly. The test conditions and configuration of the water collector are defined as 

follows: 

• Water collection medium Blotter paper 

• Weighed components Cylindrical tube made from blotter paper 

• Water used or sprayed 3.3 to 3.4 g 

• Spray brush pressure setting 30 psig 

• Spray duration 30 s 

• Spray rate 0.109 to 0.115 g/s 

• Run duration 30 s 

B.10.2 Finding. 

The results are shown in figure B-10c and table 3-10. Tests 1 to 4 used a 3.94-inch (100-mm) 

-long blotter tube, whereas tests 5 to 7 used a 3.54-inch (90-mm) blotter tube. 

Visual examination of the collector showed significant water deposition on the cylindrical blotter 

tube but none was found on the plastic container. The collection efficiencies varied from 68% to 

75%. The length of the blotter tube has negligible effects on the collection efficiencies. 

These results were similar to those obtained from configuration 9. The probe inlet pressures 

were approximately 0.8 psig (22′′H2O). Although collection efficiency data were quite 

repeatable over a small range of water spray rates, they were still well below the maximum value 

of 100%. It was thought that some of the water droplets might have escaped through the central 

exit tube (in plastic container) or simply due to evaporative loss. Therefore, it was decided to 

install a layer of desiccant materials into the plastic container to reduce these losses since 

desiccants were known to improve on the collection efficiency, e.g., configuration 6. These 

changes are described in section B.11. 

In summary, this simpler design had dispensed with the inner container and water-adsorbent 

paper from the previous configuration without incurring any loss in collection performance. And 

together with the proposed idea of installing a layer of desiccant, the design merited further 

investigations. 

B-19
Bent central exit

tube 

Plastic container 

Cylindrical 

blotter tube 

Outer container 

supports 

FIGURE B-10a. CONFIGURATION 10 

(BEFORE ASSEMBLY) 

FIGURE B-10b. CONFIGURATION 10 

(AFTER ASSEMBLY) 

0.108 0.11 0.112 0.114 0.116 0.118

Rate of spray (g/s)

0

0.2

0.4

0.6

0.8

1

Collection efficiency (%)

Installation Technique no.10

Plastic container installed

Blotter paper tube on divergent nozzle

Curve-fit

FIGURE B-10c. CONFIGURATION 10 

B-20
B.11 CONFIGURATION 11. 

B.11.1 Description. 

This is a variant of configuration 10, except for the addition of a single porous layer containing 

silica gel desiccant. The layer was fabricated by sewing two circular-shaped B-Gon fiber meshes 

together to form a pouch. Silica gel or molecular sieve pellets were poured into the pouch 

through a small opening and sealed with wire ties. This (pouch) was installed into the plastic 

container and supported by a wire mesh (diameter 0.020 inch, opening 0.030 inch, 36% 

porosity), which was placed at about 2 inches from the base of the container. A retainer ring was 

used to secure the pouch during the test. Figures B-11a and B-11b show the components of the 

water collector before and after assembly. The test conditions and configuration of the water 

collector are defined as follows: 

• Water collection medium Blotter paper, silica gel, molecular sieve, B-Gon 

• Weighed components Blotter paper, silica gel, molecular sieve, B-Gon 

• Water used or sprayed 2.8 to 3.9 g 

• Spray brush pressure setting 30 psig 

• Spray duration 30 s 

• Spray rate 0.093 to 0.131 g/s 

• Run duration 30 s 

B.11.2 Findings. 

The results are shown in figure B-11c and table 3-11. Tests 1 to 6 were conducted to assess the 

effects on the collection efficiency due to silica gel and repeated usage of the desiccants, tests 7 

to 12 assessed the effects due to different amounts of silica gel, tests 13 and 14 used molecular 

sieve, tests 15 and 16 assessed the effects on the collection efficiency due to the centrifuge, and 

test 17 used a different plastic container where the base had a number of drilled holes 

(figure B-11d). 

Visual examination of the collector showed significant water deposition on the cylindrical blotter 

tube and none was found on the plastic container. There were also some traces of water droplets 

on the B-Gon pouch. The collection efficiencies obtained varied from 72% to 116%. 

Figure B-11c shows that collection efficiencies of 100% were obtained at certain test conditions. 

It was thought that this was attributed to the desiccant materials. The following summarized 

findings were found (based on limited test data in figure B-11c): 

• Tests 1 to 6 showed that the adsorptive capability of silica gel desiccants degraded with 

repetitive usage, hence decreasing collection efficiencies. The most likely cause is the 

saturation of silica gel pellets over time. 

• Tests 7 to 12 showed that the amount of desiccant required to obtain efficiency close to 

100% must be equal to or greater than 7 g. 

B-21
• Tests 13 and 14 showed that the adsorptive capability of molecular sieve desiccants was 

slightly lower than silica gel desiccant. 

• Tests 15 and 16 showed that the addition of the centrifuge (at the divergent nozzle of the 

probe top section) degrades collection efficiency. The cause of this effect was unknown. 

Test 17 showed that using the plastic container with predrilled holes (figure B-11d) also 

degrades collection efficiency. 

The inlet static pressures recorded during tests 1 to 12 (silica gel, no centrifuge) were about 0.65 

psig (18′′H2O) compared to the pressures recorded for tests 13 and 14 (molecular sieve, no 

centrifuge) and tests 15 and 16 (silica gel and centrifuge), which were only 0.54 psig (15′′H2O). 

The inlet static pressures without the porous B-Gon layer was approximately 1.08 psig (30′′H2O). 

The large drop in the pressure was attributed to the desiccant in the porous layer and the bent exit 

tube of the plastic container used in the tests. 

Plastic container 

Outer 

container 

Silica gel inside 

B-Gon pouch 

Cylindrical 

blotter tube 

Brass retainer 

ring 

FIGURE B-11a. CONFIGURATION 11 

(BEFORE ASSEMBLY) 

FIGURE B-11b. CONFIGURATION 11 

(AFTER ASSEMBLY) 

0.09 0.1 0.11 0.12 0.13

Rate of spray (g/s)

0

0.4

0.8

1.2

Collection efficiency (%)

Installation Technique no.11

Plastic container installed

Blotter paper tube on divergent nozzle

Repeated used of silica gel (undefined quantity)

Molecular sieve in B-Gon pouch (7g)

Centrifuge installed 

Silica gel in B-Gon pouch

Repeated used of silica gel in B-Gon pouch (14g)

 

Plastic container 

bent UPVC tube 

Plastic container 

with pre-drilled 

holes 

Plastic container with 

straight UPVC tube 

FIGURE B-11c. CONFIGURATION 11 FIGURE B-11d. PLASTIC CONTAINERS WITH 

DIFFERENT EXIT DESIGNS 

B-22
B.11.3 Configuration 11 Mod-I. 

The bent exit tube of the plastic container was replaced with a straight tube, as shown in 

figure B-11d. This modification was designated as configuration 11 Mod-I. Further tests were 

conducted with this modified design but only with (approximately) 7 g of silica gel desiccants, 

which were filled the B-Gon pouch. 

The results are shown in figure B-11e and table 3-12. 

Figure B-11e shows that significant improvement in the collection efficiencies and inlet static 

pressures were obtained with the Mod-I design. The collection efficiencies vary from 96% to 

108%. The inlet static pressures were approximately 0.94 psig (26′′H2O), which represented an 

improvement of nearly 40%. The collection efficiency was also unaffected by the variation in 

the spray rates. 

In summary, based on limited data, configuration 11 Mod-I showed the highest collection 

efficiencies, which were within 100%. To quantify the measurement errors and repeatability, an 

extensive calibration test program was carried out for a wider range of flow conditions. The 

results are found in section 3.5. 

0.08 0.09 0.1 0.11 0.12

Rate of spray (g/s)

0.2

0.4

0.6

0.8

1

1.2

Collection efficiency (%)

Installation Technique no.11 Mod-I

Plastic container installed (straight exit tubing)

Blotter paper tube on divergent nozzle

Silica gel in B-Gon pouch

Curve-fit

FIGURE B-11e. CONFIGURATION 11 MOD-I 

B-23/B-24
APPENDIX C—TEST PROCEDURE FOR CONFIGURATION 11 MOD-I 

C.1 LABORATORY TEST PROCEDURE. 

1. Preparation of plastic container 

• Install container, brass ring retainer, gauze mesh, and secure to external cage 

support. 

• Place assembly inside main probe body. 

• Run for at least 1 minute to ensure the assembly is completely dry. 

2. Preparation of silica gel and B-Gon 

• Dry B-Gon filter (without any silica) using the exhaust air from the vacuum 

device. 

• Weigh the B-Gon filter and container with a lid (without silica gel). 

• Cut two (7 g) packets and sieved silica pellets with a coarse and fine gauged wire 

meshes. 

• Seal silica pellets in a container with a lid to prevent the adsorption of vapor from 

surrounding air. 

• Weigh approximately 8 g of silica gel and pour into B-Gon pouch. Seal B-Gon 

with plastic ties. 

• Place B-Gon and silica in a sealed container. 

3. Preparation of blotter paper 

• Using a new blotter paper (209 mm wide by 100 mm high), form a rolled tube 

(with a pencil) and fit onto a brass ring. 

• Place blotter over the two support brass rings (the one identified with arrow 

markings is to fit into the probe). 

• Secure both ends with elastic bands initially. Then join ends with a strong tape. 

• Blotter paper is ready for weighing. 

• Wrap blotter with a plastic bag and weigh. 

C-1
4. Preparation of water sample (for spraying) 

• Weigh and record a sample of water on electronic balance. 

• Place a lid over water holder. This is to reduce evaporation. 

5. Preparation of the test assembly 

• After weighing the blotter paper, attach to the divergent nozzle of the probe top 

section. 

• Insert blotter with the split line (i.e., the joint between two ends of the paper) 

aligned with the probe inlet. 

• At this point, the weight of the water and blotter paper have already been 

recorded. 

• Now weigh the B-Gon that contains the silica gel pellets. Ensure that the readings 

do not fluctuate. If so, leave it on the balance for a short period of time. It should 

stabilize after a while. 

• Just before placing B-Gon inside plastic container, use fingers to spread the silica 

pellet to ensure uniform distribution. Ensure pellets are also near the edges of the 

B-Gon filter. (This step must be performed with haste as vapor is being adsorb 

during this phase.) 

• Place B-Gon inside container carefully, ensuring that the B-Gon is kept level. 

• Push onto B-Gon firmly until it fits snugly onto the wire gauze. 

• Attach the brass retainer ring onto B-Gon. 

• Attach the plastic container to the probe top section (with the blotter). 

• Check to ensure the blotter paper is not pushing against the B-Gon filter (if so, 

check the height of the blotter paper to ensure it is 100 mm long). 

• Place the assembly onto the probe main body. 

6. Test procedure 

• Clean out any remaining water from the spray nozzle. 

• Check the pressure setting. 

• Using a spare water bottle, fill spray nozzle (by pressing on the spray lever). 

C-2
• Check to ensure bubbles are not caught in the water feed line. If bubbles are 

present, clean out water and refill from a spare water sample. 

• Replace the water bottle with the one to be used for testing, taking care to ensure 

that no water was lost during the changeover. 

• Start suction fan. 

• Record probe inlet static pressure readings. 

• Note start time and start spraying. 

• When set duration has been reached, stop spray and stop suction fan. 

• Remove the assembly from the main body. 

• Remove plastic container. 

• Remove B-Gon immediately and place in sealed container. 

• Remove blotter paper and place inside plastic bag to reduce evaporation. 

• Weigh and record blotter paper followed by the B-Gon. 

• Check the probe for water droplets. If present, weigh a small piece of filter paper, 

wipe the droplets with the filter paper and weigh. 

• Weigh and record a sample of water on electronic balance. 

7. Calculation of probe collection efficiency 

• Calculate the amount of water sprayed, ms. 

• Calculate the amount of water collected by blotter paper and B-Gon, mc. 

• Calculate collection efficiency, x = (mc)/ ms. 

C.2 WIND TUNNEL TEST PROCEDURE. 

Steps 1 to 4 are similar to the preparation procedures described in section C.1. 

1. Preparation of plastic container 

• Install container, brass ring retainer, gauze mesh, and secure to external cage 

support. 

• Place assembly inside main probe body. 

• Run for at least 1 minute to ensure the assembly is completely dry. 

C-3
2. Preparation of silica gel and B-Gon 

• Dry B-Gon filter (without any silica) using the exhaust air from the vacuum 

device. 

• Weigh the B-Gon filter and container with a lid (without silica gel). 

• Cut two (7 g) packets and sieved silica pellets with a coarse and fine gauged wire 

meshes. 

• Seal silica pellets in a container with a lid to prevent the adsorption of vapor from 

surrounding air. 

• Weigh approximately 8 g of silica gel and pour into B-Gon pouch. Seal B-Gon 

with plastic ties. 

• Place B-Gon and silica in a sealed container. 

3. Preparation of blotter paper 

• Using a new blotter paper (209 mm wide by 100 mm high), form a rolled tube 

(with a pencil) and fit onto a brass ring. 

• Place blotter over the two support brass rings (the one identified with arrow 

markings is to fit into the probe). 

• Secure both ends with elastic bands initially. Then join ends with a strong tape. 

• Blotter paper is ready for weighing. 

• Wrap blotter with a plastic bag and weigh. 

4. Preparation of water sample (for spraying) 

• Weigh and record a sample of water on electronic balance. 

• Place a lid over water holder. This is to reduce evaporation. 

5. Test procedure 

• Clean out any remaining water from the spray nozzle. 

• Check the pressure setting. 

• Using a spare water bottle, fill spray nozzle (by pressing on the spray lever). 

• Check to ensure bubbles are not caught in the water feed line. If bubbles are 

present, clean out water and refill from a spare water sample. 

C-4
• Replace the water bottle with the one to be used for testing, taking care to ensure 

that no water was lost during the changeover. 

• Start ISFC software. 

• Tunnel operator startup wind tunnel. 

• Tunnel operator reads out tunnel velocity in the form of a Q value (psf). 

• ISFC operator enters Q value into the DPI-610. 

• Start suction fan. 

• Record probe inlet static pressure readings. 

• Note start time and start spraying. 

• When set duration has been reached, stop spray and stop suction fan. 

• Tunnel operator stops wind tunnel. 

• Remove the assembly from the main body. 

• Remove plastic container. 

• Remove B-Gon immediately and place in the sealeable container. 

• Remove blotter paper and place inside plastic sack to reduce evaporation. 

• Weigh and record blotter paper followed by the B-Gon. 

• Check the probe for water droplets. If present, weigh a small piece of filter paper, 

wipe the droplets with the filter paper and weigh. 

• Weigh and record a sample of water on electronic balance. 

6. Calculation of probe collection efficiency 

• Calculate the amount of water sprayed, ms. 

• Calculate the amount of water collected by blotter paper and B-Gon, mc. 

• Calculate collection efficiency, x = (mc)/ ms. 

C-5/C-6
APPENDIX D—MOD-I TEST DATA—WIND TUNNEL

Line indicates 

Tunnel On

Line indicates Suction Off

Line indicates 

Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 1

Run duration = 130 s

Probe inlet static press. = 0.2 psig

LWC (approx.) = 1.35 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 2

Run duration = 130 s

Probe inlet static press. = 0.2 psig

LWC (approx.) = 1.25 g/m3

TWC probe

Wind Tunnel (simulated)

(a) Static Pressure Distribution (a) Static Pressure Distribution 

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 1

Run duration = 130 s

Probe inlet static press. = 0.2 psig

LWC (approx.) = 1.35 g/m3

TWC probe

Wind Tunnel

y

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 2

Run duration = 130 s

Probe inlet static press. = 0.2 psig

LWC (approx.) = 1.25 g/m3

TWC probe

Wind Tunnel

y

(b) Relative Humidity Distribution (b) Relative Humidity Distribution 

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 1

Run duration = 130 s

Probe inlet static press. = 0.2 psig

LWC (approx.) = 1.35 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 2

Run duration = 130 s

Probe inlet static press. = 0.2 psig

LWC (approx.) = 1.25 g/m3

TWC probe

Wind Tunnel

p

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-1. RESULTS FOR TEST 1 FIGURE D-2. RESULTS FOR TEST 2 

D-1
Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 3

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 1.05 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 4

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 1.06 g/m3

TWC probe

Wind Tunnel (simulated)

(a) Static Pressure Distribution (a) Static Pressure Distribution 

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 3

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 1.05 g/m3

TWC probe

Wind Tunnel

y

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 4

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 1.06 g/m3

TWC probe

Wind Tunnel

y

Line indicates Suction On

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Tunnel Off

(b) Relative Humidity Distribution (b) Relative Humidity Distribution 

Line indicates Tunnel On

Line indicates Suction On

Line indicates Tunnel Off

Line indicates Suction Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 3

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 1.05 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 4

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 1.06 g/m3

TWC probe

Wind Tunnel

p

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-3. RESULTS FOR TEST 3 FIGURE D-4. RESULTS FOR TEST 4 

D-2
Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 5

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.93 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 6

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.94 g/m3

TWC probe

Wind Tunnel (simulated)

(a) Static Pressure Distribution (a) Static Pressure Distribution

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 5

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.93 g/m3

TWC probe

Wind Tunnel

y

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 6

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.94 g/m3

TWC probe

Wind Tunnel

y

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 5

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.93 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 6

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.94 g/m3

TWC probe

Wind Tunnel

p

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-5. RESULTS FOR TEST 5 FIGURE D-6. RESULTS FOR TEST 6 

D-3
Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 7

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.68 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 8

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.69 g/m3

TWC probe

Wind Tunnel (simulated)

(a) Static Pressure Distribution (a) Static Pressure Distribution

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 7

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.68 g/m3

TWC probe

Wind Tunnel

y

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 8

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.69 g/m3

TWC probe

Wind Tunnel

y

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 7

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.68 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 8

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.69 g/m3

TWC probe

Wind Tunnel

p

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-7. RESULTS FOR TEST 7 FIGURE D-8. RESULTS FOR TEST 8 

D-4
0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 9

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.61 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 10

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.60 g/m3

TWC probe

Wind Tunnel (simulated)

(a) Static Pressure Distribution (a) Static Pressure Distribution

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 9

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.61 g/m3

TWC probe

Wind Tunnel

y

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 10

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.60 g/m3

TWC probe

Wind Tunnel

y

Line indicates Suction On

Line indicates Suction Off

Line indicates Tunnel On

Line indicates Tunnel Off

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 9

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.61 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 10

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.60 g/m3

TWC probe

Wind Tunnel

p

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-9. RESULTS FOR TEST 9 FIGURE D-10. RESULTS FOR TEST 10 

D-5
0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 11

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.43 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 12

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.41 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

(a) Static Pressure Distribution (a) Static Pressure Distribution

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 11

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.43 g/m3

TWC probe

Wind Tunnel

y

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 12

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.41 g/m3

TWC probe

Wind Tunnel

y

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

Line indicates Suction On

Line indicates Suction Off

Line indicates Tunnel On

Line indicates Tunnel Off

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 11

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.43 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 12

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.41 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-11. RESULTS FOR TEST 11 FIGURE D-12. RESULTS FOR TEST 12 

D-6
0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 13

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.39 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 14

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.28 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

(a) Static Pressure Distribution (a) Static Pressure Distribution

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 13

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.39 g/m3

TWC probe

Wind Tunnel

y

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 14

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.28 g/m3

TWC probe

Wind Tunnel

y

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

Line indicates Suction On

Line indicates Suction Off

Line indicates Tunnel On

Line indicates Tunnel Off

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 13

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.39 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 14

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.28 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-13. RESULTS FOR TEST 13 FIGURE D-14. RESULTS FOR TEST 14 

D-7
Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 15

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.26 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 16

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.25 g/m3

TWC probe

Wind Tunnel (simulated)

(a) Static Pressure Distribution (a) Static Pressure Distribution

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 15

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.26 g/m3

TWC probe

Wind Tunnel

y

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 16

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.25 g/m3

TWC probe

Wind Tunnel

y

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 15

Run duration = 130 s

Probe inlet static press. = 0.25 psig

LWC (approx.) = 0.26 g/m3

TWC probe

Wind Tunnel

p

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

28

32

36

40

44

48

Temperature (oC)

 Test number 16

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.25 g/m3

TWC probe

Wind Tunnel

p

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-15. RESULTS FOR TEST 15 FIGURE D-16. RESULTS FOR TEST 16 

D-8
Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 17

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.24 g/m3

TWC probe

Wind Tunnel (simulated)

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 18

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 1.22 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Suction Off

Line indicates Suction On

(a) Static Pressure Distribution (a) Static Pressure Distribution 

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

10

20

30

40

50

Relative humidity (%)

 Test number 17

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.24 g/m3

TWC probe

Wind Tunnel

y

0 100 200 300 400 500 600

Time (s)

40

42

44

46

48

50

Relative humidity (%)

 Test number 18

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 1.22 g/m3

TWC probe

Wind Tunnel

y

Line indicates Suction Off

Line indicates Suction On

(b) Relative Humidity Distribution (b) Relative Humidity Distribution 

Line indicates Tunnel On

Line indicates Suction Off

Line indicates Suction On

Line indicates Tunnel Off

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 17

Run duration = 130 s

Probe inlet static press. = 0.30 psig

LWC (approx.) = 0.24 g/m3

TWC probe

Wind Tunnel (simulated)

0 100 200 300 400 500 600

Time (s)

26

28

30

32

34

Temperature (oC)

 Test number 18

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 1.22 g/m3

TWC probe

Wind Tunnel

p

Line indicates Suction Off

Line indicates Suction On

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-17. RESULTS FOR TEST 17 FIGURE D-18. RESULTS FOR TEST 18 

D-9
0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 19

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.77 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Suction Off

Line indicates Suction On

0 100 200 300 400 500 600

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 20

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.70 g/m3

TWC probe

Wind Tunnel (simulated)

Line indicates Suction Off

Line indicates Suction On

(a) Static Pressure Distribution (a) Static Pressure Distribution

0 100 200 300 400 500 600

Time (s)

40

42

44

46

48

50

Relative humidity (%)

 Test number 19

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.77 g/m3

TWC probe

Wind Tunnel

y

0 100 200 300 400 500 600

Time (s)

40

42

44

46

48

50

Relative humidity (%)

 Test number 20

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.70 g/m3

TWC probe

Wind Tunnel

y

Line indicates Suction Off

Line indicates Suction Off

Line indicates Suction On Line indicates Suction On

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

0 100 200 300 400 500 600

Time (s)

26

28

30

32

34

Temperature (oC)

 Test number 19

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.77 g/m3

TWC probe

Wind Tunnel

p

Line indicates Suction Off

Line indicates Suction On

0 100 200 300 400 500 600

Time (s)

26

28

30

32

34

Temperature (oC)

 Test number 20

Run duration = 130 s

Probe inlet static press. = 0.20 psig

LWC (approx.) = 0.70 g/m3

TWC probe

Wind Tunnel

p

Line indicates Suction Off

Line indicates Suction On

 (c) Temperature Distribution (c) Temperature Distribution 

FIGURE D-19. RESULTS FOR TEST 19 FIGURE D-20. RESULTS FOR TEST 20 

D-10
APPENDIX E—MOD-II TEST DATA—LABORATORY 

0 100 200 300 400 500 600 700

Time (s)

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 1

Run duration = 600 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.24 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Line indicates Suction Off

Line indicates Suction On Line indicates Suction Off

Line indicates Suction On

0 100 200 300 400 500

Time (s)

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 2

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.27 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

(a) Static Pressure Distribution (a) Static Pressure Distribution 

0 100 200 300 400 500 600 700

Time (s)

46

48

50

52

54

56

58

60

62

Relative humidity (%)

 Test number 1

Run duration = 600 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.24 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

y

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates Suction Off

Line indicates 

Suction On

0 100 200 300 400 500

Time (s)

46

48

50

52

54

56

58

60

62

Relative humidity (%)

 Test number 2

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.27 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

y

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates 

Suction Off

Line indicates 

Suction On

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

0 100 200 300 400 500 600 700

Time (s)

22.5

23

23.5

24

24.5

25

25.5

Temperature (oC)

 Test number 1

Run duration = 600 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.24 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

p

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates Suction Off

Line indicates 

Suction On

0 100 200 300 400 500

Time (s)

22.5

23

23.5

24

24.5

25

Temperature (oC)

 Test number 2

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.27 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

p

Line indicates 

Suction Off

Line indicates 

Suction On

Ambient (Spray Test)

Ambient (Dry Test)

(c) Temperature Distribution 

FIGURE E-1. RESULTS FOR TEST 1 

(c) Temperature Distribution 

FIGURE E-2. RESULTS FOR TEST 2 

E-1
Line indicates Suction Off

Line indicates Suction On

0 100 200 300 400 500

Time (s)

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 3

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.99 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

0 100 200 300 400 500

Time (s)

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 4

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.55 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Line indicates Suction Off

Line indicates Suction On

(a) Static Pressure Distribution (a) Static Pressure Distribution

0 100 200 300 400 500

Time (s)

46

48

50

52

54

56

58

60

62

Relative humidity (%)

 Test number 3

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.99 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

y

Line indicates 

Suction Off

Line indicates 

Suction On

Ambient (Spray Test)

Ambient (Dry Test)

0 100 200 300 400 500

Time (s)

48

50

52

54

56

58

60

Relative humidity (%)

 Test number 4

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.55 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

y

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates

Suction Off

Line indicates

Suction On

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

0 100 200 300 400 500

Time (s)

21.5

22

22.5

23

23.5

24

24.5

25

25.5

Temperature (oC)

 Test number 3

Run duration = 300 s

Probe inlet static press. = 0.90 psig

LWC (approx.) = 0.99 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

p

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates

Suction Off

Line indicates 

Suction On

0 100 200 300 400 500

Time (s)

21

22

23

24

25

Temperature (oC)

 Test number 4

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.55 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

p

Line indicates

Suction Off

Line indicates

Suction On

Ambient (Spray Test) Ambient (Dry Test)

(c) Temperature Distribution 

FIGURE E-3. RESULTS FOR TEST 3 

(c) Temperature Distribution 

FIGURE E-4. RESULTS FOR TEST 4 

E-2
0 100 200 300 400 500

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 5

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.53 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Line indicates Suction Off

Line indicates Suction On

0 100 200 300 400 500

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 6

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.60 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Line indicates Suction Off

Line indicates Suction On

(a) Static Pressure Distribution (a) Static Pressure Distribution

0 100 200 300 400 500

Time (s)

48

50

52

54

56

58

60

62

64

Relative humidity (%)

 Test number 5

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.53 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

y

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates 

Suction Off

Line indicates 

Suction On

0 100 200 300 400 500

Time (s)

48

50

52

54

56

58

60

62

64

Relative humidity (%)

 Test number 6

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.60 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

y

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates 

Suction Off

Line indicates 

Suction On

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

0 100 200 300 400 500

Time (s)

21

22

23

24

25

26

27

Temperature (oC)

 Test number 5

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.53 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

p

0 100 200 300 400 500

Time (s)

21

22

23

24

25

26

Temperature (oC)

 Test number 6

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.60 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

p

Line indicates 

Suction On

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates

Suction Off

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates 

Suction On

Line indicates

Suction Off

(c) Temperature Distribution 

FIGURE E-5. RESULTS FOR TEST 5 

(c) Temperature Distribution 

FIGURE E-6. RESULTS FOR TEST 6 

E-3
0 100 200 300 400 500

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 7

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.68 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Line indicates Suction Off

Line indicates Suction On

0 100 200 300 400 500

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 8

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 2.10 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Line indicates Suction Off

Line indicates Suction On

(a) Static Pressure Distribution (a) Static Pressure Distribution

0 100 200 300 400 500

Time (s)

48

50

52

54

56

58

60

62

64

Relative humidity (%)

 Test number 7

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.68 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

y

Ambient (Spray Test)

Ambient (Dry Test) Line indicates

Suction Off

Line indicates

Suction On

0 100 200 300 400 500

Time (s)

52

54

56

58

60

62

64

66

68

Relative humidity (%)

 Test number 8

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 2.10 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

y

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates Suction Off

Line indicates

Suction On

Spray Off

(b) Relative Humidity Distribution (b) Relative Humidity Distribution

0 100 200 300 400 500

Time (s)

21

22

23

24

25

26

Temperature (oC)

 Test number 7

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 1.68 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

p

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates

Suction Off

Line indicates

Suction On

0 100 200 300 400 500

Time (s)

20

21

22

23

24

25

Temperature (oC)

 Test number 8

Run duration = 300 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 2.10 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

p

Line indicates Suction Off

Line indicates

Suction On

Ambient (Spray Test) Ambient (Dry Test)

Spray Off

(c) Temperature Distribution 

FIGURE E-7. RESULTS FOR TEST 7 

(c) Temperature Distribution 

FIGURE E-8. RESULTS FOR TEST 8 

E-4
0 100 200 300 400 500

Time (s)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Static pressure (psig)

 Test number 9

Run duration = 420 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 2.56 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

Line indicates Suction Off

Line indicates Suction On

(a) Static Pressure Distribution 

0 100 200 300 400 500

Time (s)

52

54

56

58

60

62

64

66

68

Relative humidity (%)

 Test number 9

Run duration = 420 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 2.56 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

y

Ambient (Spray Test)

Ambient (Dry Test)

Line indicates

Suction Off

Line indicates

Suction On

Spray Off

(b) Relative Humidity Distribution 

0 100 200 300 400 500

Time (s)

20

21

22

23

24

25

26

Temperature (oC)

 Test number 9

Run duration = 420 s

Probe inlet static press. = 0.40 psig

LWC (approx.) = 2.56 g/m3

Expt. data (Dry Test)

Expt. data (Spray Test)

p

Line indicates Suction Off

Line indicates

Suction On

Ambient (Spray Test) Ambient (Dry Test)

Spray Off

(c) Temperature Distribution 

FIGURE E-9. RESULTS FOR TEST 9 

E-5/E-6
APPENDIX F—FUNDAMENTAL HUMIDITY EQUATIONS 

The following describes the humidity relationships that were used to calculate the amount of 

evaporated water that had entered the reference probe (also known as ingress water). They are 

written as follows: 

 ) (T / E ERH = satv (F-1) 

= dv = ) {E / R (R / M MW vLv v )} / (P - E (F-2) 

sp hv = / M M RH (F-3) 

Defining 

h = + dv ) M (M M (F-4) 

Therefore 

= +1 

= +

) / M (M

 ) / M M (M /MM

dv

dh ddv (F-5) 

Substituting equation F-2 gives 

=W + 1 (F-6) 

Rewriting equation F-3 and substitute equation F-4 gives 

sp = dhdv = +1) W/(W) /M)/(M /M (M RH (F-7) 

Hence, 

v sp h = × M RH M (F-8) 

where, 

RH = relative humidity (recorded by humidity sensor) 

Ev = vapour pressure (contributed by the ambient vapor and/or evaporated mass from a 

spray cloud) 

Esat(T) = saturated vapor pressure at a given temperature 

W = mixing ratio (grams of water vapor/grams of dry air) 

(Rv/RL) = ratio of gas constant of water vapor and dry air (= 0.622) 

F-1
P = ambient pressure 

RHsp = specific humidity (ratio of the mass of water vapor (g) to the mass of humid air 

(g)) 

Mv = mass of water vapor (contributed by the ambient vapor and/or evaporated mass 

from a spray cloud) 

Mh = mass of humid air (environmental air consisted of water vapor and dry air) 

Md = mass of dry air 

F-2