Influence of Concentration and Additives

on R123/Paraffinic Material Oil Boiling

Heat Transfer Performance

Mark A. Kedzierski

D.H. Han

NISTIR 7336

NISTIR 7336

Influence of Concentration and Additives on

R123/Paraffinic Material Oil Boiling Heat

Transfer Performance

Mark A. Kedzierski

U.S DEPARTMENT OF COMMERCE

National Institute of Standard and Technology

Building Environment Division

Building and Fire Research Laboratory

Gaithersburg, MD 20899-8631

D.H. Han

Institute of Advanced Machinery Design

Korea University, 136-701

Seoul, Korea

September 2006

U.S. Department of Commerce

Carlos M. Gutierrez, Secretary

National Institute of Standards and Technology

William A. Jeffrey, Director

1

Influence of Additives and Concentration on R123/Paraffinic Mineral 

Oil Pool Boiling Heat Transfer 

M. A. Kedzierski 

National Institute of Standards and Technology 

Bldg. 226, Rm B114 

Gaithersburg, MD 20899 

Phone: (301) 975-5282 

Fax: (301) 975-8973 

D.H. Han 

Institute of Advanced Machinery Design 

Korea University, 136-701 

Seoul, Korea 

ABSTRACT 

This report investigates the effect that oil concentration had on the boiling performance of an 

R123/paraffinic mineral oil mixture on a roughened, horizontal flat surface. For all 

compositions (0.5 %, 1 %, and 2 %), the lubricant caused a heat transfer degradation relative 

to the heat transfer of pure R123 of between 2 % and 70 % for the range of measured heat 

fluxes. The heat transfer degradation was shown to increase with lubricant mass fraction. 

The minimum heat transfer degradation for each mixture ranged between 2 % and 12 % and 

occurred at approximately 20 kW/m2

. For a given composition, the heat transfer degradation 

increased as the heat flux increased from roughly 20 kW/m2 to 90 kW/m2. In addition, the 

effect of two trial additives on the pool boiling heat transfer of an R123/paraffinic mineral oil 

mixture was examined in order to test the validity of a theory for choosing oil additives to 

enhance boiling performance. The verification tests were inconclusive. More research with 

lubricants and additives with greater differences in surface tensions is required to develop a 

more rigorous and quantifiable theory for designing additives that improve boiling heat transfer. 

Keywords: refrigerants, additives, boiling, enhanced heat transfer, refrigerant/lubricant 

mixtures, paraffinic mineral oil 
2

TABLE OF CONTENTS 

ABSTRACT........................................................................................................................ 1 

Table of Contents ................................................................................................................ 2 

List of figures ...................................................................................................................... 2 

List of tables........................................................................................................................ 2 

INTRODUCTION............................................................................................................... 4 

APPARATUS ..................................................................................................................... 5

TEST SURFACE ................................................................................................................ 5 

MEASUREMENTS AND UNCERTAINTIES.................................................................. 5 

EXPERIMENTAL RESULTS............................................................................................ 6 

ADDITIVE DISCUSSION ................................................................................................. 8 

CONCLUSIONS................................................................................................................. 9 

ACKNOWLEDGEMENTS .............................................................................................. 10 

NOMENCLATURE.......................................................................................................... 11 

English Symbols............................................................................................................ 11 

Greek symbols............................................................................................................... 11 

English Subscripts......................................................................................................... 11 

REFERENCES.................................................................................................................. 12 

APPENDIX A: ADDITIVE POTENTIAL....................................................................... 30 

APPENDIX B: UNCERTAINTIES.................................................................................. 33 

APPENDIX C: LIQUID DENSITY MEASUREMENTS................................................ 35 

APPENDIX D: CAPILLARY RISE MEASUREMENTS ............................................... 40 

APPENDIX E: LUBRICANT VISCOSITY MEASUREMENTS ................................... 42 

LIST OF FIGURES 

Fig. 1 Schematic of test apparatus.................................................................................... 23 

Fig. 2 OFHC copper flat test plate with cross-hatched surface and thermocouple coordinate 

system.................................................................................................................... 24 

Fig. 3 Pure R123 boiling curve for plain surface ............................................................. 25 

Fig. 4 R134a /PARA mixtures boiling curves for plain surface ...................................... 26 

Fig. 5 R123/PARA/PG (97.8/2/0.2) boiling curve for plain surface................................ 27 

Fig. 6 R123/PARA/LP1 (97.8/2/0.2) boiling curve for plain surface.............................. 28 

Fig. 7 R123/PARA mixture heat fluxes relative to that of pure R123 for a plain surface29 

Fig. 8 R123/PARA/PG (97.8/2/0.2) and R123/PARA/LP1 (97.8/2/0.2) mixture heat fluxes 

relative to that of the R123/PARA (98/2) mixture for a plain surface.................. 30 

Fig. A.1 Efficiency of centrifugal chillers at industry rating conditions (Fischer et al., 1994)

............................................................................................................................... 32 

Fig. A.2 R11 water chiller COP improvement for a given evaporator enhancement ...... 33 

Fig. B.1 Expanded relative uncertainty in the heat flux of the surface at the 95 % confidence 

level ....................................................................................................................... 34 

Fig. B.2 Expanded uncertainty in the temperature of the surface at the 95 % confidence level

............................................................................................................................... 35 

LIST OF TABLES 
3

Table 1 Base lubricant and additive properties ................................................................ 13 

Table 2 Conduction model choice.................................................................................... 13 

Table 3 Pool boiling data ................................................................................................. 14 

Table 4 Number of test days and data points ................................................................... 19 

Table 5 Estimated parameters for cubic boiling curve fits for plain copper surface ....... 19 

Table 6 Residual standard deviation of ∆Ts ..................................................................... 20 

Table 7 Average magnitude of 95 % multi-use confidence interval for mean Tw-Ts(K) . 21 

Table C.1 PARA liquid density measurements................................................................ 36 

Table C.2 PG liquid density measurements ..................................................................... 36 

Table C.3 LP1 Liquid Density Measurements................................................................. 38 

Table C.4 Density coefficients for eq. C.1....................................................................... 39 

Table D.1 Capillary rise measurements for LP1 .............................................................. 41 

Table D.2 Capillary rise measurements for PG................................................................ 41 

Table D.3 Capillary rise measurements for PARA.......................................................... 41 

Table E.1 Kinematic viscosity measurements for PARA ................................................ 42 

Table E.2 Kinematic viscosity measurements for PG...................................................... 42 

Table E.3 Kinematic viscosity measurements for LP1 .................................................... 42 
4

INTRODUCTION 

The quest for understanding how lubricants and lubricant additives influence pool boiling has 

always been important in terms of how lubricants affect the design of efficient, affordable 

and reliable equipment. Improving the efficiency of existing air-conditioning equipment has 

been significantly emphasized with the recent blackout of the U.S. Northeast and escalating 

energy and copper costs. Increased accuracy in the sizing of evaporators affords the 

opportunity for using less copper in evaporators. Consequently, every trustworthy 

refrigerant/lubricant pool boiling heat transfer measurement can contribute to the pursuit of a 

fundamental boiling model. In addition, as illustrated in Appendix A, a refrigerant oil 

additive that improves water chiller efficiency could be a cost-effective and immediate means 

of reducing operating costs and improving the reliability of (reduced demand on) our nation’s 

electricity grid. Because of this, agencies in the US federal government have been interested 

in the possibility of using additives to improve chiller performance. Toward this end, NIST1

(Kedzierski, 2004 & 2006) has proposed a theory with a purpose of selecting lubricants that 

when added to the base lubricant of an existing chiller will improve the pool boiling 

performance. 

As shown by Kedzierski (2001c), the viscosity, miscibility and concentration of the lubricant 

strongly influence refrigerant/lubricant pool boiling. The properties of the lubricant closest 

to the wall essentially control the boiling. Consequently, if an additive (or added lubricant) is 

to have an impact on a given refrigerant/lubricant system, there would be a greater likelihood 

for influence if the additive can exist as a monolayer on the surface. If the additive is wellmixed in the lubricant excess layer (which is likely for a chemically similar additive and 

lubricant), it will have minimal influence on the heat transfer if it is only 2 % by mass of the 

lubricant (typical additive charge). For this reason, two of the three basic rules for an 

additive to potentially enhance boiling heat transfer, according to the NIST hypothesis, are 

concerned with determining if a monolayer forms or not. According to the theory, the two 

requirements for a monolayer to form are: (1) the liquid-vapor surface tension of the additive 

should be larger than that of the base lubricant, and (2) the base lubricant and the additive 

must be “chemically dissimilar.” At this point in time, these rules are not well defined. For 

example, it is not known how large of a difference between surface-tensions is required. In 

addition, synthetic lubricant and mineral oil are sufficiently different to satisfy the 

“chemically dissimilar” definition, but this may not be true for all cases. The third and final 

rule for enhancement is that the viscosity of the additive must be larger than that of the base 

lubricant. However, an additive with larger viscosity than the base lubricant will potentially 

induce an enhancement in boiling heat transfer only if it forms a monolayer. In other words, 

all three rules or conditions must be satisfied before a lubricant can have the potential of 

being an effective additive. 

The primary goals of this study were to (1) attempt to verify or disprove the NIST rules for 

selecting lubricants to improve pool boiling heat transfer, and (2) to contribute 

R123/lubricant pool boiling data to the literature in support of improved boiling modeling. 

The base lubricant chosen for use with R123 was a paraffinic mineral oil with a nominal 

kinematic viscosity of 85 μm2

/s at 297.8 K. Paraffinic oils are typically used for ammonia 

applications and less typically with other low pressure refrigerants like R123. The primary 

 

1

 NIST (National Institute of Standards and Technology) is part of the U.S. Department of Commerce. 
5

reason for the selection of this particular paraffinic mineral was because it had the smallest 

liquid-vapor surface tension with a room temperature viscosity larger than 60 μm

2

/s of all 

lubricants that were found in an extensive search of various mineral oils. By choosing a base 

lubricant with a small surface tension and a large viscosity, the opportunity for finding additives 

to enhance the boiling performance was improved. Following the NIST additive rules for 

enhancing pool boiling heat transfer, two synthetic oils were chosen (PG and LP1) as additives 

that had both larger viscosity and larger surface tension than the paraffinic base lubricant. Table 

1 shows that the viscosity of the two oils that were used as additives were approximately 150 

μm

2

/s and 2000 μm

2

/s at 297.8 K for PG and LP1, respectively. Also shown in Table 1 is that 

the surface tensions are only nominally 5 % larger than that of the paraffinic (30.6 μm

2

/s ± 0. 

7 μm

2

/s). 

APPARATUS 

Figure 1 shows a schematic of the apparatus that was used to measure the pool boiling data 

of this study. More specifically, the apparatus was used to measure the liquid saturation 

temperature (Ts), the average pool-boiling heat flux (q"), and the wall temperature (Tw) of the 

test surface. The three principal components of the apparatus were the test chamber, the 

condenser, and the purger. The internal dimensions of the test chamber were 25.4 mm × 257 

mm × 1.54 m. The test chamber was charged with approximately 7 kg of refrigerant, giving 

a liquid height of approximately 80 mm above the test surface. As shown in Fig. 1, the test 

section was visible through two opposing, flat 150 mm × 200 mm quartz windows. The 

bottom of the test surface was heated with high velocity (2.5 m/s) water flow. The vapor 

produced by liquid boiling on the test surface was condensed by the brine-cooled, shell-andtube condenser and returned as liquid to the pool by gravity. Further details of the test 

apparatus can be found in Kedzierski (2002a) and Kedzierski (2001a). 

TEST SURFACE 

Figure 2 shows the oxygen-free high-conductivity (OFHC) copper flat test plate used in this 

study. The test plate was machined out of a single piece of OFHC copper by electric 

discharge machining (EDM). A tub grinder was used to finish the heat transfer surface of the 

test plate with a crosshatch pattern. Average roughness measurements were used to estimate 

the range of average cavity radii for the surface to be between 12 μm and 35 μm. The 

relative standard uncertainty of the cavity measurements were approximately ± 12 %. 

Further information on the surface characterization can be found in Kedzierski (2001a). 

MEASUREMENTS AND UNCERTAINTIES 

The standard uncertainty (ui) is the positive square root of the estimated variance ui

2

. The 

individual standard uncertainties are combined to obtain the expanded uncertainty (U), which 

is calculated from the law of propagation of uncertainty with a coverage factor. All 

measurement uncertainties are reported at the 95 % confidence level except where specified 

otherwise. For the sake of brevity, only an outline of the basic measurements and 

uncertainties is given below. Complete detail on the heat transfer measurement techniques 

and uncertainties can be found in Kedzierski (2000a) and Appendix B, respectively. 
6

All of the copper-constantan thermocouples and the data acquisition system were calibrated 

against a glass-rod standard platinum resistance thermometer (SPRT) and a reference voltage 

to a residual standard deviation of 0.005 K. Considering the fluctuations in the saturation 

temperature during the test and the standard uncertainties in the calibration, the expanded 

uncertainty of the average saturation temperature was no greater than 0.04 K. Consequently, 

it is believed that the expanded uncertainty of the temperature measurements was less than 

0.1 K. 

Twenty 0.5 mm diameter thermocouples were force fitted into the wells of the side of the test 

plate shown in Fig. 2. The heat flux and the wall temperature were obtained by regressing 

the measured temperature distribution of the block to the governing two-dimensional 

conduction equation (Laplace equation). In other words, rather than using the boundary 

conditions to solve for the interior temperatures, the interior temperatures were used to solve 

for the boundary conditions following a backward stepwise procedure given in Kedzierski 

(1995)2

. Fourier's law and the fitted constants from the Laplace equation were used to 

calculate the average heat flux (q") normal to and evaluated at the heat transfer surface based 

on its projected area. The average wall temperature (Tw) was calculated by integrating the 

local wall temperature (T). The wall superheat was calculated from Tw and the measured 

temperature of the saturated liquid (Ts). Considering this, the relative expanded uncertainty in 

the heat flux (Uq") was greatest at the lowest heat fluxes, approaching 10 % of the 

measurement near 10 kW/m2. In general, the Uq" remained approximately within 3 % and 6 

% for heat fluxes greater than 30 kW/m2. The average random error in the wall superheat 

(UTw) was between 0.04 K and 0.1 K. Plots of Uq" and UTw versus heat flux can be found in 

Appendix B. 

EXPERIMENTAL RESULTS 

The heat flux was varied roughly between 10 kW/m2

 and 100 kW/m2 to simulate a range of 

possible operating conditions for R123 chillers. All pool-boiling tests were taken at 277.6 K 

saturated conditions. The data were recorded consecutively starting at the largest heat flux 

and descending in intervals of approximately 4 kW/m2

. The descending heat flux procedure 

minimized the possibility of any hysteresis effects on the data, which would have made the 

data sensitive to the initial operating conditions. Table 3 presents the measured heat flux and 

wall superheat for all the data of this study. Table 4 gives the number of test days and data 

points for each fluid. 

The mixtures were prepared by charging the test chamber (see Fig. 1) with pure R123 to a 

known mass. Next, a measured mass of lubricant was injected with a syringe through a port 

in the test chamber. The refrigerant/lubricant solution was mixed by flushing pure refrigerant 

through the same port where the lubricant was injected. After the tests with the 

refrigerant/lubricant mixture were completed, the additive was added to the existing test 

chamber charge in the same manner as for the lubricant. Additives were added to the 

refrigerant/lubricant (98/2) mixture as roughly 10 % of the existing mass of lubricant in the 

system giving an R123/PARA/ PG (97.8/2/0.2) mixture and an R123/PARA/LP1 (97.8/2/0.2) 

mixture. All compositions were determined from the masses of the charged components and 

 

2

 For the record, Table 2 provides functional forms of the Laplace equation that were used in this study in the 

same way as was done in Kedzierski (1995) and in similar studies by this author. 
7

are given on a mass fraction percent basis. The maximum uncertainty of the composition 

measurement is approximately 0.02 %, e.g., the range of a 2.0 % composition is between 

1.98 % and 2.02 %. Nominal or target mass compositions are used in the discussion. For 

example, the “actual” mass composition of the PARA in the R123/PARA (99.5/0.5) mixture 

was 0.54 % ± 0.02 %. Likewise, the PARA mass fractions for R123/PARA (99/1) and the 

R123/PARA (98/2) mixtures were 0.98 % ± 0.02 % and 1.99 % ± 0.02 %, respectively. 

Using the same uncertainties, the additive mixtures as tested were R123/PARA/ PG 

(97.90/1.97/0.13) and R123/PARA/LP1 (97.87/1.94/0.19). 

Figure 3 is a plot of the measured heat flux (q") versus the measured wall superheat (Tw - Ts) 

for pure R123 at a saturation temperature of 277.6 K. The opened circles represent six days 

of boiling measurements made over a period of approximately one week. The solid lines 

shown in Fig. 3 are cubic best-fit regressions or estimated means of the data. Three of the 

107 measurements were removed before fitting because they were identified as “outliers” 

based on having both high influence and high-leverage (Belsley et al., 1980). Table 5 gives 

the constants for the cubic regression of the superheat versus the heat flux for all of the fluids 

tested here. The residual standard deviation of the regressions - representing the proximity of 

the data to the mean - are given in Table 6. The dashed lines to either side of the mean 

represent the lower and upper 95 % simultaneous (multiple-use) confidence intervals for the 

mean. From the confidence intervals, the expanded uncertainty of the estimated mean wall 

superheat was 0.26 K and 0.04 K for superheats less than and greater than 14.5 K, 

respectively. Table 7 provides the average magnitude of 95 % multi-use confidence interval 

for the fitted wall superheat for all of the test data. 

 

Figure 4 plots the measured heat flux (q") versus the measured wall superheat (Tw - Ts) at a 

saturation temperature of 277.6 K for the three R123/PARA mixtures. Comparison of the 

three boiling curves shows that they are within 2 kW/m2

 of each other and the pure R123 

performance at a superheat of approximately 11 K. For mean superheats greater than 11 K, 

the boiling heat transfer degradation with respect to pure R123 boiling heat transfer increases 

with increasing lubricant concentration. This is an expected trend as outlined in Kedzierski 

(2001c) because the bubble size becomes smaller for increasing lubricant mass fraction, 

which leads to a reduction in heat transfer if the site density does not increase enough to 

compensate for the loss of vapor generation per bubble. 

Figure 5 is a plot of the measured heat flux (q") versus the measured wall superheat (Tw - Ts) 

for the R123/PARA/PG (97.8/2/0.2) mixture at a saturation temperature of 277.6 K. The 

open diamonds represent over 50 boiling measurements made over three consecutive days. 

For comparison, the mean of the R123/PARA (98/2) mixture boiling curve is provided as a 

coarsely dashed, gray line. The average expanded uncertainty of the estimated mean wall 

superheat for superheats greater and less than 15.5 K was 0.14 K and 0.46 K, respectively. 

Figure 6 is a plot of the measured heat flux (q") versus the measured wall superheat (Tw - Ts) 

for the R123/PARA/LP1 (97.8/2/0.2) mixture at a saturation temperature of 277.6 K. The 

open stars represent 126 boiling measurements made over four days within a week. For 

comparison, the mean of the R123/PARA (98/2) mixture boiling curve is provided as a 

coarsely dashed, gray line. The average expanded uncertainty of the estimated mean wall 

superheat for superheats greater and less than 15.5 K was 0.11 K and 0.31 K, respectively. 
8

A more detailed comparison of the R123/PARA and the R123/PARA/additive heat transfer 

performances the relative to R123 and R123/PARA (98/2), respectively, is given in Figs. 7 

and 8. Figure 7 plots the ratio of the R123/PARA mixture heat flux to the pure R123 heat 

flux (q"m/q"p) versus the pure R123 heat flux (q"p) at the same wall superheat. Figure 7 

illustrates the influence of lubricant mass composition on the R123/PARA boiling curve with 

solid lines representing the mean heat flux ratios for each mixture. Overall, lubricant for all 

compositions has caused a heat transfer degradation relative to the heat transfer of pure R123 

for all measured heat fluxes. The degradation is shown to increase with lubricant mass 

fraction. For example, the average heat flux ratio for the R123/PARA (99.5/0.5), the 

R123/PARA (99/1), and the R123/PARA (98/2) mixture from approximately 15 kW/m2 to 

100 kW/m2 was 0.64, 0.55, and 0.48, respectively. The minimum heat transfer degradation 

for each mixture (or the maximum heat transfer) is shown on Fig. 7 to be at approximately 

20 kW/m2

. For 20 kW/m2, the heat flux ratio for the R123/PARA (99.5/0.5), the 

R123/PARA (99/1), and the R123/PARA (98/2) mixture is 0.98 ± 0.02, 0.90 ± 0.025, and 

0.88 ± 0.02, respectively. The lubricant effect becomes more pronounced as the heat flux 

increases from roughly 20 kW/m2

 to 90 kW/m2 producing heat flux ratios of approximately 

0.52, 0.4, and 0.3 at 90 kW/m2

 for the R123/PARA (99.5/0.5), the R123/PARA (99/1), and 

the R123/PARA (98/2) mixtures, respectively. 

Figure 8 details the effect that the additives had on the R123/PARA (98/2) boiling curve. 

The figure plots the ratio of the R123/PARA/PG (97.8/2/0.2) heat flux to the R123/PARA 

(98/2) heat flux (q"m/q"2%) versus the R123/PARA (98/2) mixture heat flux (q"2%) at the 

same wall superheat. Likewise, the R123/PARA/LP1 (97.8/2/0.2) heat flux to the 

R123/PARA (98/2) heat flux (q"m/q"2%) versus the R123/PARA (98/2) mixture heat flux 

(q"2%) at the same wall superheat is also plotted. A heat transfer enhancement exists where 

the heat flux ratio is greater than one and the 95 % simultaneous confidence intervals 

(depicted by the shaded regions) do not include the value one. Figure 8 shows that for heat 

fluxes less than 85 kW/m2, neither additive causes an enhancement of R123/PARA (98/2) 

pool boiling heat transfer. For the most part, either a degradation or no measurable 

difference is observed compared to the R123/PARA (98/2) mixture. A small 5 % 

enhancement of the heat flux is obtained for the R123/PARA/LP1 (97.8/2/0.2) mixture at a 

heat flux of approximately 90 kW/m2

. Similarly, the R123/PARA/PG (97.8/2/0.2) mixture 

shows a maximum heat flux ratio of 1.03 at a heat flux of approximately 27 kW/m2

. 

However, because the confidence intervals include the value of one at the maximum, no 

difference between the mixture/additive performance and that of the mixture can be 

established. Overall, the average heat flux ratio for the R123/PARA/LP1 (97.8/2/0.2) 

mixture from approximately 7 kW/m2 to 89 kW/m2 was 0.95. Likewise, the average heat 

flux ratio for the R123/PARA/PG (97.8/2/0.2) mixture from approximately 9 kW/m2

 to 81 

kW/m2 was 0.97. 

ADDITIVE DISCUSSION 

The heat transfer results summarized in Fig. 8, for the most part, show that the lubricants 

chosen as additives had little or no effect on the boiling performance of the R123/mineral oil 

(98/2) system. However, considering that the rules provided by the NIST additive hypothesis 

are not precisely quantified, the preceding heat transfer results cannot be used to prove or 

disprove the basic premise of the hypothesis. The main reason for this is that it cannot be 
9

known if the surface-tension difference between the additive and the base lubricant was 

sufficient enough to cause the formation of an additive monolayer. As Table 1 shows, the 

differences in the mean kinematic viscosity appears to be significant enough and with 

satisfactorily small uncertainties for a viscosity effect to be present. However, the surfacetension differences between the base lubricant and the additives are marginal at best. In fact, 

the LP1 lubricant exhibits nearly no difference in surface tension between it and the PARA 

(1.1 mN/m ± 1 mN/m) when the measurement uncertainties are taken into consideration. As 

a result, when considering LP1 as a potential additive, the evidence is not sufficient to 

suggest that the surface tension difference was significant enough for the LP1 to form a 

monolayer at the surface. Consequently, if a monolayer is not formed, then the benefits of a 

larger viscosity cannot be realized because LP1 is only 10 % of the mass of the base 

lubricant.3

 Also, although the positive difference in surface tension between PG and the base 

lubricant is statistically significant (1.6 mN/m ± 1 mN/m), the difference may not be large 

enough. There may be a critical difference in surface tensions that must be attained before a 

monolayer a can be formed. In support of this, when Kedzierski (2004) observed a heat 

transfer enhancement with additives, there was an accompanying difference in surface 

tension of 3 mN/m ± 1.4 mN/m, which is approximately 88 % larger than the surface tension 

difference between the present base mineral oil and PG. 

Future research is required to investigate the influence of the magnitude of the surfacetension difference on boiling heat transfer performance. In addition, there may be other 

primary lubricant property effects that govern an additive’s influence on boiling other than 

surface tension, viscosity, and chemical similarity with the base lubricant. For example, 

additive polarity and miscibility may play more of a primary role along with heat transfer. In 

other words, how the thermal boundary layer interacts with the excess layer and its properties 

should be studied. Further investigation into the above effects may lead to a more rigorous and 

quantifiable theory that can be used to develop additives that improve boiling heat transfer for 

the benefit of the refrigeration and air-conditioning industry. 

 

CONCLUSIONS 

The effect of paraffinic mineral oil concentration on the boiling performance of 

R123/paraffinic mineral oil mixtures on a roughened, horizontal flat surface was 

investigated. For all compositions, the lubricant caused a heat transfer degradation relative to 

the heat transfer of pure R123 for all measured heat fluxes. The heat transfer degradation 

was shown to increase with lubricant mass fraction. The minimum heat transfer degradation 

for each mixture occurred at approximately 20 kW/m2

. For a given composition, the heat 

transfer degradation increased as the heat flux increases from roughly 20 kW/m2 to 

90 kW/m2. 

The effect of two trial additives on the pool boiling heat transfer of an R123/paraffinic 

mineral oil mixture was examined in order to test the validity of a theory for choosing oil 

additives to enhance boiling performance. In general, the specific lubricants chosen as 

additives had little or no effect on the boiling performance of the R123/mineral oil mixture. 

 

3

 In addition, the Kedzierski (2001) showed a linear heat transfer enhancement with respect to increasing 

viscosity only between roughly 5 cSt and 200 cSt. Consequently, extrapolation of the effect of a 2000 cSt on 

heat transfer is not justified. In other words, a heat transfer maximum may exist with respect to viscosity for 

some viscosity greater than 200 cSt. 
10

However, because the rules provided by the NIST additive theory are not precisely 

quantified, the heat transfer results could not be used to prove or disprove the basic premise 

of the hypothesis. The main reason for this is that it is not known if the surface-tension 

difference between the additive and the base lubricant was sufficient enough to cause the 

formation of an additive monolayer. Future research with greater differences in surface 

tensions is required to investigate the influence of the magnitude of the surface-tension 

difference on boiling heat transfer performance in order to develop a more rigorous and 

quantifiable theory that can be used to design additives that improve boiling heat transfer. 

ACKNOWLEDGEMENTS 

This work was funded by NIST. Thanks go to the following NIST personnel for their 

constructive criticism of the first draft of the manuscript: Dr. S. Treado, and Dr. P. 

Domanski. Thanks goes to the N. Sawant of the Catholic University of America for his 

constructive criticism of the second draft of the manuscript. Furthermore, the authors extend 

appreciation to W. Guthrie and Mr. A. Heckert of the NIST Statistical Engineering Division 

for their consultations on the uncertainty analysis. The lubricant property measurements 

were made by Dr. M. Gong of the Chinese Academy of Sciences while he was a Guest 

Researcher at NIST. Both the PG (EMKAROX DGLF118) and the LP1 (Hypermer LP1, a 

polycondensed fatty acid separated from its solid phase at room temperature) were donated 

by Dr. S. Randles of Uniqema and were much appreciated. 
11

NOMENCLATURE 

English Symbols

An regression constant in Table 5 n=0,1,2,3 

Co viscometer calibration constant, μm

2

 s

-1

COP Coefficient of Performance 

d liquid pool height, m 

ECOP percent increase in COP

Eh percent increase in h 

g gravitational acceleration, m s-2

h heat transfer coefficient, W K-1 m

-2

l capillary rise height, m 

Ly length of test surface (Fig. 2), m 

LMTD Log-Mean-Temperature-Difference, K 

P vapor pressure, kPa 

q" average wall heat flux, W m-2 

r radius of capillary tube, m 

T temperature, K 

Tw temperature at roughened surface, K 

U expanded uncertainty 

ui standard uncertainty 

X model terms given in Table 2 

Greek symbols

∆T temperature difference, K 

∆Ts wall superheat: Tw - Ts, K 

∆ν difference between base lubricant and additive kinematic viscosity, m2 s

-1 

∆ρ difference between liquid and vapor density, kg m-3

∆σ difference between base lubricant and additive surface tension, kg s-2

ν kinematic viscosity, m2 s

-1

σ surface tension, kg s-2

English Subscripts

B baseline 

Bc condenser baseline 

Be evaporator baseline 

c condenser 

e evaporator 

m mixture 

p pure R123 

q" heat flux 

r refrigerant-side 

s saturated state 

Tw wall temperature 

v vapor 

w wall or water-side 

2% R123/PARA (98/2) 
12

REFERENCES 

Adamson, A. W., and Gast, A. P., 1997, Physical Chemistry of Surfaces, Interscience Publ., 

New York, 6th Ed., p. 11. 

Belsley, D. A., Kuh, E., and Welsch, R. E., 1980, Regression Diagnostics: Identifying 

Influential Data and Sources of Collinearity, New York: Wiley. 

Fischer, S. K, Tomlinson, J. J., and Hughes, T. J., 1994, "Energy and Global Warming 

Impact of Not-in-kind and Next Generation CFC and HCFC Alternatives," US DOE and 

Alternative Fluorocarbons Environmental Acceptability Study (AFEAS) report, Washington, 

DC. 

Incropera, F. P., and DeWitt, D. P., 1985, Fundamentals of Heat and Mass Transfer, 2nd ed., 

John Wiley & Sons, New York. 

Kedzierski, M. A., 2006, “Effect of Refrigerant Oil Additive on R134a and R123 Boiling Heat 

Transfer Performance,” accepted for Int. J. Refrigeration. 

Kedzierski, M. A, 2004, “Effect of Refrigerant Oil Additive on R134a and R123 Boiling Heat 

Transfer Performance and Related Issues for GSA,” NISTIR 7132, U.S. Department of 

Commerce, Washington, D.C. 

Kedzierski, M. A., 2002a, “Use of Fluorescence to Measure the Lubricant Excess Surface 

Density During Pool Boiling,” Int. J. Refrigeration, Vol. 25, pp.1110-1122. 

Kedzierski, M. A., 2001a, “Use of Fluorescence to Measure the Lubricant Excess Surface 

Density During Pool Boiling,” NISTIR 6727, U.S. Department of Commerce, Washington, 

D.C. 

Kedzierski, M. A., 2001c, “The Effect of Lubricant Concentration, Miscibility and Viscosity 

on R134a Pool Boiling” Int. J. Refrigeration, Vol. 24, No. 4., pp. 348-366. 

Kedzierski, M. A., 2000a, “Enhancement of R123 Pool Boiling by the Addition of 

Hydrocarbons,” Int. J. Refrigeration, Vol. 23, pp. 89-100. 

Kedzierski, M. A., 2000b, “The Effect of a Boiling Additive on R123 Condensation on a 

Vertical Integral-Fin Surface,” Int. J. Refrigeration, Vol. 23, pp. 101-111. 

Kedzierski, M. A., 1995, “Calorimetric and Visual Measurements of R123 Pool Boiling on 

Four Enhanced Surfaces,” NISTIR 5732, U.S. Department of Commerce, Washington. 
13

Table 1 Base lubricant and additive properties4

T = 297.8 K

Lubricant ν (μm

2

/s) ∆ν (μm

2

/s) σ (mN/m) ∆σ (mN/m) ρ (kg/m3) 

Paraffinic 

Mineral oil 

(PARA) 

85 ± 1.5 0 30.6 ± 0. 7 0 877 

DGLF118 

(PG) 

150.3 ± 0.8 65 ± 1.8 32.2 ± 0. 7 1.6 ± 1 996 

LP1 2000 ± 500 1915 ± 500 31.7 ± 0. 7 1.1 ± 1 920 

Table 2 Conduction model choice 

X0= constant (all models) X1= x X2= y X3= xy 

X4=x

2

-y

2

X5= y(3x2-y

2

) X6= x(3y2-x

2

) X7= x

4

+y4-6(x2)y2 

 X8= yx

3

-xy

3

Fluid Most frequent models 

Pure R123 

(file: pR23ad.dat) 

X1,X5 (40 of 100) 40 % 

X1,X2,X4(38 of 100) 38 % 

X1,X2 (9 of 100) 9 % 

R123/PARA (99.5/0.5) 

(file: 5PARA.dat) 

X1,X2,X4 (42 of 88) 48 % 

X1,X5 (18 of 88) 20 % 

X1,X5,X6 (13 of 88) 15 % 

R123/PARA (99/1) 

(file: PARA1.dat) 

X1,X2,X4 (46 of 84) 55 % 

X1,X5,X6(18 of 84) 21 % 

X1,X2, X4,X6 (8 of 84) 9 % 

X1,X2, X5,X6 (8 of 84) 9 % 

R123/PARA (98/2) 

(file: PARA2.dat) 

X1,X2,X4 (43 of 158)27 % 

X1,X2 (30 of 158) 19 % 

X1,X2,X4,X6 (28 of 158) 18 % 

R123/PARA/PG (97.8/2/0.2) 

(file: PARAPG.dat) 

X1, X2 (13 of 52) 25 % 

X1,X2,X4 (12 of 52) 23 % 

X1,X2,X4,X6 (12 of 52) 23 % 

R123/PARA/LP1 (97.8/2/0.2) 

(file: PARALP1.dat) 

X1,X2 (26 of 117) 22 % 

X1,X2,X6 (26 of 117) 22 % 

X1,X2,X4,X6 (25 of 117) 21 % 

 

4

 Density, surface tension, and viscosity measurements and measurement methodologies are given in 

Appendixes C, D, and E, respectively. 
14

Table 3 Pool boiling 

data 

Pure R123 

File: PR123AD.dat ∆Ts (K) q" (W/m2

) 

 16.17 100368.4

 15.45 78680.3

 15.12 67248.9

 14.77 56119.3

 14.30 37624.5

 13.95 31120.5

 12.47 22070.1

 10.76 16734.0

 8.58 14901.5

 16.64 112156.3

 16.18 98384.2

 15.92 90476.4

 15.51 76815.4

 15.13 64511.2

 14.81 54653.3

 14.55 43565.7

 13.95 31386.2

 12.56 22460.8

 16.35 103370.6

 16.23 100019.3

 16.08 96101.5

 15.80 88879.3

 15.63 84008.8

 15.48 78704.8

 15.33 73348.2

 15.21 69058.7

 15.09 64392.0

 14.99 60255.1

 14.86 55006.2

 14.70 48673.3

 14.58 44497.1

 14.38 38647.8

 14.26 36376.0

 14.04 32718.7

 13.79 29494.6

 13.23 25765.9

 12.78 23379.9

 12.22 21538.6

 11.67 19322.6

 10.98 17817.9

 10.25 16245.2

 9.40 15030.1

 8.33 14709.5

 7.68 13942.2

 16.37 102380.8

 15.93 91408.9

 15.50 75842.0

 15.21 66140.9

 15.10 62536.8

 14.97 57355.2

 14.68 46509.4

 14.53 41071.2

 14.12 32630.9

 13.63 27627.0

 12.68 23272.9

 11.20 17978.9

 9.65 15246.2

 8.71 14019.7

 16.07 98119.3

 15.81 90121.4

 15.63 84306.2

 15.43 76463.5

 15.25 69072.8

 15.09 62320.9

 14.88 52351.0

 14.59 42825.2

 14.11 33951.4

 13.51 27336.2

 12.40 21992.4

 11.62 19572.1

 10.62 16715.3

 9.45 15004.9

 15.99 94152.9

 15.68 84632.4

 15.42 75696.8

 15.17 65575.6

 15.02 58770.2

 14.71 45918.8

 14.33 35843.3

 13.87 29357.6

 12.89 23521.2

 12.16 20811.2

 11.28 18084.1

 10.50 16298.5

 9.21 15759.4

 7.46 12867.5

 15.99 94152.9

 15.68 84632.4

 15.42 75696.8

 15.17 65575.6

 15.02 58770.2

 14.71 45918.8

 14.33 35843.3

 13.87 29357.6

 12.89 23521.2

 12.16 20811.2

 11.28 18084.1

 10.50 16298.5

 9.206 15759.4

 7.460 12867.5

R123/PARA (99.5/0.5) 

File: 5PARA.dat ∆Ts (K) q" (W/m

2

) 

 17.664 86194.2 

 17.232 76725.6 

 16.911 69740.7 

 16.507 60527.9 

 16.183 52047.5 

 15.817 42105.5 

 15.278 31945.6 

 14.461 26278.3 

 13.058 21748.3 

 11.481 18073.6 

 17.110 73547.5 

 16.903 70136.6 

 16.642 64810.8 

 16.459 60912.1 

 16.332 56797.3 

 16.268 56529.1 

 16.308 58731.8 

 16.183 58840.4 

 16.055 54914.5 

 15.872 49986.0 

 15.582 43960.3 

 15.302 38495.0 

 15.015 33827.9 

 14.682 29441.2 

 14.270 26576.7 

 13.510 23877.1 

 12.782 22250.2 

 11.999 19818.2 

 11.461 17850.9 

 10.613 16655.9 

 10.021 15740.2 

 17.416 81537.8 

 16.956 72659.9 

 16.607 65639.2 

 16.240 55665.9 

 15.907 48123.2 

 15.410 38185.6 

 14.695 30002.1 

 13.719 24581.0 

 12.221 20327.8 

 10.717 17344.8 

 18.035 92753.1 

 17.750 90300.5 

 17.491 85067.9 

 17.378 82792.4 
 15

 17.25 79952.9 

 16.96 75044.6 

 16.75 70968.0 

 16.58 67178.5 

 16.39 62727.5 

 16.26 58627.3 

 15.94 51559.9 

 15.68 46759.2 

 15.46 41663.5 

 15.25 37751.8 

 14.91 32855.5 

 14.52 29218.9 

 14.11 26473.1 

 13.76 24825.1 

 12.87 22337.7 

 12.15 20477.8 

 11.50 18253.8 

 10.72 16771.0 

 9.92 15538.7 

 17.85 90809.5 

 17.65 85605.7 

 17.44 82533.2 

 17.24 78095.9 

 17.00 73202.1 

 16.85 70359.4 

 16.63 65716.1 

 16.46 61887.3 

 16.32 56457.7 

 16.14 52339.8 

 15.89 47270.1 

 15.73 43672.6 

 15.38 35947.9 

 15.13 32716.9 

 14.57 28877.7 

 14.16 26596.6 

 13.61 24508.0 

 12.90 22830.8 

 12.12 20499.8 

 11.28 17806.6 

 10.87 17195.3 

 9.76 15340.7 

 8.91 15609.1 

 8.26 14183.3 

R123/PARA (99/1) 

File: PARA1.dat

∆Ts (K) q" (W/m2

) 

 17.68 75831.4

 17.63 71742.8

 17.35 69074.2

 17.13 62849.3

 16.95 58990.7

 16.78 55396.2

 16.51 50041.3

 16.23 43677.3

 16.03 39797.6

 15.74 35256.6

 15.43 31264.7

 15.02 28124.8

 14.40 25478.0

 13.87 23623.7

 13.06 21604.0

 12.48 18678.9

 11.69 17106.4

 11.04 16371.9

 17.41 64517.6

 17.32 61863.5

 17.12 56781.2

 16.95 53041.5

 16.76 48928.1

 16.53 44841.3

 16.13 38162.6

 15.74 32984.7

 15.52 31178.9

 15.00 27672.6

 14.42 25976.2

 13.68 23317.2

 12.90 21472.4

 12.30 19314.3

 11.67 18122.7

 10.72 16335.0

 17.22 64996.6

 17.05 60878.2

 16.89 55928.6

 16.78 52846.7

 16.64 50047.8

 16.39 45036.8

 16.00 38143.9

 15.69 33788.0

 15.39 30959.9

 14.94 27888.8

 14.28 25700.9

 13.84 23574.9

 12.98 21268.0

 12.27 18893.0

 11.41 17142.5

 10.71 16247.3

 17.18 66620.4

 17.03 63457.5

 16.88 58939.9

 16.70 55018.3

 16.50 51612.1

 16.22 44861.1

 16.05 41313.2

 15.71 36456.3

 15.56 31728.8

 15.16 28466.4

 14.67 25443.1

 14.08 24533.2

 13.31 21221.9

 12.79 19039.8

 18.43 84802.5

 18.11 82192.9

 17.94 79721.8

 17.72 75552.6

 17.53 69660.9

 17.37 65943.8

 17.16 61173.9

 16.94 56753.6

 16.73 53066.8

 16.43 46066.2

 16.31 42924.9

 16.04 38178.5

 15.66 33027.6

 15.36 30603.3

 14.77 26860.2

 14.20 24435.6

 13.34 21353.5

 12.89 19534.6

 12.44 17915.7

 11.90 17695.6

R123/PARA (98/2) 

File: PARA2.dat 

∆Ts (K) q" (W/m2

) 

 19.03 83387.4

 18.77 79517.8

 18.51 78362.9

 18.29 74699.3

 18.10 70731.8

 17.89 66273.3

 17.77 63057.3

 17.61 56225.6

 17.33 50990.2

 17.23 44741.7

 16.98 40372.8

 16.82 36872.2

 16.43 31815.0

 15.97 28419.7

 15.49 25853.3

 14.72 23156.1

 14.13 20519.0

 13.31 18755.6

 12.88 18562.9

 19.78 95822.0

 19.52 92292.0
 16

 19.19 87838.2

 18.93 84015.5

 18.26 74593.4

 18.02 71477.4

 17.87 69277.5

 17.59 62637.3

 17.56 56851.1

 17.48 52302.9

 17.45 48898.7

 17.24 41903.4

 17.01 37837.1

 16.60 33814.1

 16.18 30798.7

 15.63 26934.0

 15.05 24590.6

 14.42 23108.4

 13.56 19595.5

 12.91 18480.1

 12.05 16921.1

 11.25 15891.5

 10.61 14821.6

 9.81 13390.9

 8.81 13599.6

 7.90 11941.8

 7.15 10606.2

 6.16 9127.1

 5.27 8011.9

 19.42 88436.1

 19.02 84910.8

 18.76 81030.3

 18.51 77337.9

 18.26 72599.3

 18.15 70010.0

 17.96 65204.6

 17.83 61350.6

 17.60 54246.4

 17.45 50539.8

 17.31 46453.7

 16.97 39327.8

 16.81 35554.5

 16.44 32084.5

 15.96 28182.7

 15.49 25665.9

 14.76 23358.0

 13.91 20772.3

 13.35 19171.3

 12.53 17979.8

 11.80 16548.0

 10.94 15306.8

 10.23 14232.3

 9.30 14241.0

 8.28 12582.3

 7.47 11296.8

 6.32 9213.9

 19.24 85892.6

 19.10 84642.4

 18.64 79518.1

 18.47 77001.8

 18.19 72456.9

 18.02 69026.1

 17.88 65529.0

 17.72 59168.1

 17.63 55344.3

 17.40 49898.0

 17.26 46552.3

 16.88 39142.2

 16.63 35488.3

 16.38 32455.1

 15.90 28873.8

 15.41 25719.0

 14.74 23656.2

 14.13 22044.5

 13.25 19225.7

 12.82 18730.2

 11.88 16996.5

 11.14 15829.8

 10.26 14265.3

 9.52 14849.8

 8.61 13192.6

 7.52 11152.0

 6.71 9958.1

 5.71 8222.8

 4.83 6959.6

 19.81 93462.0

 19.53 89920.9

 19.22 85222.4

 18.89 80249.8

 18.52 76806.3

 18.33 73813.5

 18.09 68867.9

 17.93 63321.6

 17.67 56584.9

 17.45 50035.4

 17.23 46732.0

 17.11 41355.3

 16.91 36750.4

 16.49 32462.1

 16.08 29618.5

 15.44 25913.0

 14.73 23778.7

 13.77 20145.0

 13.35 19221.5

 12.70 18377.0

 11.96 16964.0

 11.10 15608.3

 10.38 14639.0

 9.51 14787.0

 8.77 13531.7

 7.33 10996.5

 6.42 9841.2

 5.58 8364.7

 4.98 7316.8

 18.01 60573.2

 17.77 55233.9

 17.35 42191.6

 16.84 35597.2

 16.03 29410.9

 14.80 23427.8

 13.31 18698.2

 11.67 15529.4

 9.65 14070.5

 19.10 88600.6

 18.54 78050.7

 18.12 69518.7

 17.99 61993.4

 17.72 54150.4

 17.48 48425.1

 17.17 40315.8

 16.56 32595.3

 15.64 26737.2

 14.67 23216.7

 13.04 18663.5

 11.66 16062.9

 10.15 13633.6

 8.71 12798.0

 6.39 9744.0

 4.38 6160.1

R123/PARA/PG 

File: PARAPG.dat

∆Ts (K) q" (W/m2

) 

 18.52 75389.6

 18.23 67941.5

 17.99 61941.4

 17.86 56776.8

 17.56 48877.0

 17.34 42323.0

 16.82 34914.2

 16.10 29003.0

 14.79 23543.3

 13.77 20023.4

 12.76 17490.1

 11.83 16423.1

 10.71 14579.4

 9.36 13928.2

 7.80 11373.6
 17

 19.02 84018.0

 18.65 75652.9

 18.15 66693.6

 17.92 58932.5

 17.61 51510.6

 17.41 46376.2

 16.87 35430.5

 16.03 28370.9

 15.03 24682.7

 14.18 20935.8

 12.82 17658.9

 11.74 16640.8

 10.40 14333.0

 9.33 14362.0

 7.93 11714.6

 6.77 10059.1

 5.32 7513.8

 19.16 87538.1

 18.76 78591.6

 18.40 73569.1

 18.18 69209.6

 17.90 60218.3

 17.45 50465.8

 17.11 42807.8

 16.71 35346.1

 16.17 30489.8

 15.34 25240.7

 14.43 22394.0

 13.72 20650.6

 12.75 17390.0

 11.41 15767.1

 10.20 13738.0

 8.92 13443.6

 7.58 11163.3

 6.30 9265.5

 5.14 7398.3

 4.05 5600.9

R123/PARA/LP1 

File: PARALP1.dat 

∆Ts (K) q" (W/m2

) 

 18.93 89371.8

 18.59 84675.3

 18.45 81828.4

 18.15 75327.7

 18.12 74006.9

 17.98 69674.6

 17.92 66965.8

 17.81 60515.6

 17.74 56478.3

 17.66 52470.4

 17.44 47686.9

 17.06 40883.3

 16.80 37061.0

 16.35 32252.7

 15.85 28673.4

 15.34 26367.2

 14.78 24009.5

 14.25 21373.1

 13.53 19633.5

 12.74 17577.6

 12.10 17057.8

 11.23 15305.1

 10.63 13994.6

 9.69 14196.0

 8.70 12823.5

 7.85 11436.2

 6.61 9505.7

 5.99 8574.8

 5.01 6623.5

 19.23 91803.1

 19.04 88783.1

 18.90 86129.4

 18.58 78884.7

 18.52 78047.5

 18.36 72119.5

 18.21 68119.0

 18.07 63441.8

 17.95 58799.6

 17.74 52206.4

 17.67 49223.3

 17.59 46295.3

 17.35 41618.4

 17.01 37346.6

 16.54 32411.0

 16.12 29224.1

 15.48 25891.6

 14.90 23755.9

 13.97 20633.4

 13.43 19148.5

 12.64 17142.7

 12.00 16381.3

 11.149 14920.9

 10.52 13956.0

 9.63 13938.6

 8.63 12325.7

 7.84 11077.7

 6.83 9357.8

 5.73 7869.8

 19.08 87687.1

 18.95 85005.1

 18.72 80083.1

 18.54 73853.9

 18.45 71163.1

 18.31 67215.6

 18.27 64663.6

 18.06 56897.8

 17.99 55930.6

 17.76 49788.2

 17.53 45156.3

 17.30 40516.9

 17.09 37004.0

 16.76 34149.3

 16.19 29284.3

 15.51 25451.6

 14.84 21753.2

 14.38 20863.4

 13.70 19321.7

 12.88 17273.9

 12.13 15616.9

 11.46 15193.7

 10.63 13767.7

 9.84 14429.7

 9.08 12974.0

 8.02 11342.2

 7.16 10146.2

 6.18 8621.0

 5.34 7167.0

 19.25 91824.0

 19.06 87816.6

 18.96 83937.5

 18.75 80362.6

 18.59 76691.3

 18.44 70509.9

 18.33 67611.1

 18.20 63075.5

 18.07 58622.3

 17.91 54519.7

 17.69 49531.2

 17.54 46166.8

 17.16 39532.2

 16.97 37176.3

 16.523 32528.1

 16.15 29667.3

 15.46 25655.2

 14.78 23302.4

 14.11 20965.2

 13.56 19763.9

 12.78 17707.7

 12.10 16904.5

 11.35 15062.3

 10.51 13720.9

 9.74 14207.6

 8.91 12817.9

 7.64 11120.5

 7.02 9972.6
 18

 6.02 8178.3

 4.85 6413.4
 19

Table 4 Number of test days and data points 

Fluid (% mass fraction) Number of days Number of data points 

Pure R123 

7.5 K ≤ ∆Ts ≤ 16.5 K 

6 100 

R123/PARA (99.5/0.5) 

9 K ≤ ∆Ts ≤ 18 K 

5 88 

R123/PARA (99/1) 

10.5 K ≤ ∆Ts ≤ 18 K 

5 84 

R123/PARA (98/2) 

5 K ≤ ∆Ts ≤ 20 K 

7 158 

R123/PARA/PG (97.8/2/0.2) 

5 K ≤ ∆Ts ≤ 19 K 

3 52 

R123/PARA/LP1 (97.8/2/0.2) 

5 K ≤ ∆Ts ≤ 19.5 K 

4 117 

Table 5 Estimated parameters for cubic boiling curve fits for plain copper surface 

∆Ts = A0 + A1 q” + A2 q”2 + A3 q”3 

∆Ts in Kelvin and q” in W/m2

Fluid Ao A1 A2 A3

PureR123 

6 K ≤ ∆Ts ≤ 14.5 K 

14.5 K ≤ ∆Ts ≤ 16.5 K 

-13.5834

11.9188 

2.48902x10-3 

9.93197x10-5

-7.70987x10-8 

-1.13967x10-9

8.18448x10-13 

5.77704x10-15

R123/PARA (99.5/0.5) 

9 K ≤ ∆Ts ≤ 15.5 K 

14.5 K ≤ ∆Ts ≤ 18 K 

-6.90657

11.7559 

1.60725x10-3 

1.44116x10-4

-3.93167x10-8 

-1.63992x10-9

3.27067x10-13 

8.78834x10-15

R123/PARA (99/1) 

10.5 K ≤ ∆Ts ≤ 16 K 

15.5 K ≤ ∆Ts ≤ 18 K 

-1.62317

11.9169 

1.11913x10-3 

1.68801x10-4

-2.31487x10-8 

-2.05499x10-9

1.54542x10-13 

1.11276x10-14

R123/PARA (98/2) 

5 K ≤ ∆Ts ≤ 16.5 K 

15 K ≤ ∆Ts ≤ 20 K 

-2.68251

8.98216 

1.04636x10-3

3.90307x10-4

-8.12573x10-9

-6.10689x10-9

-1.92917x10-13

3.41756x10-14

R123/PARA/PG (97.8/2/0.2) 

5 K ≤ ∆Ts ≤ 16 K 

15 K ≤ ∆Ts ≤ 19 K 

3.79045 

8.90035 

-3.55922x10-4

3.95287x10-4

8.78467x10-8

-6.14104x10-9

-2.24414x10-12

3.43387x10-14

R123/PARA/LP1 (97.8/2/0.2) 

5 K ≤ ∆Ts ≤ 17 K 

15 K ≤ ∆Ts ≤ 19.5 K 

-3.67750

8.87760 

1.34398x10-3

3.85489x10-4

-2.67061x10-8

-5.62173x10-9

1.38544x10-13

2.89907x10-14
 20

Table 6 Residual standard deviation of ∆Ts

Fluid u (K) 

PureR123 

6 K ≤ ∆Ts ≤ 14.5 K 

14.5 K ≤ ∆Ts ≤ 16.5 K 

0.27 

0.05 

R123/PARA (99.5/0.5) 

9 K ≤ ∆Ts ≤ 15.5 K 

14.5 K ≤ ∆Ts ≤ 18 K 

0.23 

0.10 

R123/PARA (99/1) 

10.5 K ≤ ∆Ts ≤ 16 K 

15.5 K ≤ ∆Ts ≤ 18 K 

0.21 

0.11 

R123/PARA (98/2) 

5 K ≤ ∆Ts ≤ 16.5 K 

15 K ≤ ∆Ts ≤ 20 K 

0.35 

0.11 

R123/PARA/PG (97.8/2/0.2) 

5 K ≤ ∆Ts ≤ 16 K 

15 K ≤ ∆Ts ≤ 19 K 

0.33 

0.10 

R123/PARA/LP1 (97.8/2/0.2) 

5 K ≤ ∆Ts ≤ 17 K 

15 K ≤ ∆Ts ≤ 19.5 K 

0.38 

0.13 
 21

Table 7 Average magnitude of 95 % multi-use confidence interval for mean Tw -Ts(K) 

Fluid u (K) 

PureR123 

6 K ≤ ∆Ts ≤ 14.5 K 

14.5 K ≤ ∆Ts ≤ 16.5 K 

0.26 

0.04 

R123/PARA (99.5/0.5) 

9 K ≤ ∆Ts ≤ 15.5 K 

14.5 K ≤ ∆Ts ≤ 18 K 

0.24 

0.09 

R123/PARA (99/1) 

10.5 K ≤ ∆Ts ≤ 16 K 

15.5 K ≤ ∆Ts ≤ 18 K 

0.22 

0.10 

R123/PARA (98/2) 

5 K ≤ ∆Ts ≤ 16.5 K 

15 K ≤ ∆Ts ≤ 20 K 

0.26 

0.08 

R123/PARA/PG (97.8/2/0.2) 

5 K ≤ ∆Ts ≤ 16 K 

15 K ≤ ∆Ts ≤ 19 K 

0.46 

0.14 

R123/PARA/LP1 (97.8/2/0.2) 

5 K ≤ ∆Ts ≤ 17 K 

15 K ≤ ∆Ts ≤ 19.5 K 

0.31 

0.11 
22

 

Fig. 1 Schematic of test apparatus 
 23

 

Fig. 2 OFHC copper flat test plate with cross-hatched surface and thermocouple 

coordinate system 
 24

Fig. 3 Pure R123 boiling curve for plain surface 
 25

Fig. 4 R134a /PARA mixtures boiling curves for plain surface 
 26

Fig. 5 R123/PARA/PG (97.8/2/0.2) boiling curve for plain surface 
 27

Fig. 6 R123/PARA/LP1 (97.8/2/0.2) boiling curve for plain surface 
 28

 

Fig. 7 R123/PARA mixture heat fluxes relative to that of pure R123 for a plain 

surface 
 29

Fig. 8 R123/PARA/PG (97.8/2/0.2) and R123/PARA/LP1 (97.8/2/0.2) mixture heat 

fluxes relative to that of the R123/PARA (98/2) mixture for a plain surface 
 30

APPENDIX A: ADDITIVE POTENTIAL 

This appendix presents the results of a thermodynamic cycle and heat transfer analysis to 

determine the potential improvement in chiller coefficient of performance (COP) as 

caused by a given improvement in refrigerant side boiling heat transfer. The design 

conditions and operating specifications of a representative 1110 kW (315 ton), R11 

chiller manufactured in the year 1985 was chosen as the baseline and taken from the 

manufacturer’s catalog data. The entering and exiting sink and source temperatures were 

taken from design conditions for the chiller and held constant throughout the analysis. 

The entering and leaving condenser water temperature was 302.6 K and 307.9 K, 

respectively. The entering and leaving evaporator water temperature was 285.4 K and 

279.8 K, respectively. The baseline Log-Mean-Temperature-Difference of the condenser 

(LMTDBc) and that of the evaporator (LMTDBe) before additive treatment was 5.6 K and 

3.4 K, respectively. Figure A.1 taken from Fischer et al. (1994), roughly confirms the 

representative value of the reported COP for the baseline chiller at approximately 5.65 for 

the year 1985. The analysis assumed isenthalphic expansion and adiabatic compression 

at an isentropic efficiency of 0.721. The compressor efficiency was chosen so that the 

cycle would match the quoted COP of the baseline chiller and was held constant 

throughout the analysis. 

The split of the water-side/refrigerant-side heat transfer resistance for the evaporator of 

the baseline chiller was found to be 68 %/32 %. In other words, the refrigerant-side 

temperature difference (∆Tr) and the water-side temperature difference (∆Tw) were 68 % 

and 32 % of the LMTD, respectively: 

LMTD 0.32LMTD 0.68LMTD =∆ +∆ = + T T r w BB (A.1) 

The percent increase in the refrigerant-side heat transfer coefficient (Eh) was used to 

reduce the magnitude of the refrigerant-side heat transfer resistance while maintaining the 

magnitude of the original baseline water-side resistance. Hence, the improved LMTD for 

the evaporator was calculated as: 

e B

0.32 LMTD 0.68 LMTD

1

100

Eh

   

= +  

  +  

 (A.2) 

Kedzierski (2000b) has shown that a boiling additive can degrade the condensation heat 

transfer by as much as 10 %. Based on this, it was assumed that the additive caused a 

10 % reduction in the refrigerant-side heat transfer coefficient in the condenser. The 

LMTD for the condenser was calculated as: 

c Bc Bc Bc

0.32 LMTD 0.68LMTD LMTD 1.04LMTD

0.9

=+ ≈ (A.3) 

Figure A.2 shows the percent increase in the COP (ECOP) for a given Eh and the 

assumptions of the analysis. Because of the heat transfer degradation in the condenser, 
 31

performance improvements are not realized until the evaporator heat transfer enhanced 

by more than 25 %. The figure also shows that if the boiling performance of a 

representative 1985 chiller could be improved by 100 %, the chiller would realize an 

improvement of approximately 1 % in the COP. The chiller COP would be improved by 

approximately 1.5 % for an Eh of 225 %. 

Figure A.2 also shows the Eh for the case where there is no condenser penalty for heat 

transfer degradation as caused by the additive. A 10 % reduction in the refrigerant-side 

heat transfer coefficient in the condenser has caused approximately a 0.7 % loss in COP 

for Eh between 25 % and 275 %. 

Fig. A.1 Efficiency of centrifugal chillers at industry rating 

conditions (Fischer et al., 1994) 
 32

 

Fig. A.2 R11 water chiller COP improvement for a given evaporator 

enhancement 
 33

APPENDIX B: UNCERTAINTIES 

Figure B.1 shows the relative (percent) uncertainty of the heat flux (Uq") as a function of 

the heat flux. Figure B.2 shows the uncertainty of the wall temperature as a function of 

heat flux. The uncertainties shown in Figs. B.1 and B.2 are "within-run uncertainties." 

These do not include the uncertainties due to "between-run effects" or differences 

observed between tests taken on different days. The "within-run uncertainties" include 

only the random effects and uncertainties associated with one particular test. All other 

uncertainties reported in this study are "between-run uncertainties" which include all 

random effects such as surface past history or seeding. 

 

Fig. B.1 Expanded relative uncertainty in the heat flux of the surface at the 95 % 

confidence level 
 34

Fig. B.2 Expanded uncertainty in the temperature of the surface at the 95 % 

confidence level 
 35

APPENDIX C: LUBRICANT LIQUID DENSITY MEASUREMENTS 

This appendix presents the measurements and the correlation of the PARA, PG, and LP1 

lubricant liquid densities (ρl). The density of the liquid lubricant was measured as a 

function of temperature with a glass pycnometer. The pycnometer was factory 

instrumented with a glass mercury thermometer with a range of 14 °C to 38 °C in 0.2 ° 

graduations, accurate to within ± 0.2 K. The pycnometer was filled with distilled water 

and its volume was calculated from the known density of water. The volume was found 

with 29 trails to be 9.588 ml with a standard uncertainty of 0.002 ml. The average mass 

of the pycnometer after nine trials was 28.794 g ± 0.001 g. 

The pycnometer containing the test lubricant was cooled in an ice bath and then removed 

from the bath and allowed to warm on the balance to room temperature over 

approximately one hour. The standard uncertainty of the balance was approximately 

1 mg. The outside of the pycnometer was wiped clean before each measurement to 

remove the lubricant that was expelled through the pipette due to volume expansion with 

temperature increase. 

The Biot number for the warming pycnometer was estimated to be approximately 0.5, 

which is greater than the recommended limit of 0.1 (Incropera and Dewitt, 1985) for a 

uniform temperature in fluid. It is difficult to estimate the error introduced in the 

measurements due to temperature gradients that existed in the lubricant. However, the 

data regression shows that the residuals are independent of temperature, which suggests 

that the error due to temperature gradients in the liquid had a negligible effect on the 

density measurements. 

Tables C.1 through C.3 shows the recorded measurements for the three test lubricants. 

Equation C.1 gives the fit of the liquid lubricant density (ρl) in kg/m3

 versus temperature 

(T) in Kelvin: 

l 0 1 ρ = − a a T C.1 

Where the coefficients for each lubricant are given in Table C.4. The expanded 

uncertainty of the fits were approximately ± 1 kg/m3

 for 95 % confidence. 
 36

Table C.1 PARA liquid density measurements 

T (°C) Lubricant mass (g) ρl (kg/m3) 

14.6 8.466 882.96 

17.2 8.449 881.19 

18 8.446 880.88 

19 8.441 880.36 

20.2 8.436 879.83 

21.4 8.428 879.00 

22 8.424 878.58 

22.8 8.418 877.96 

23.6 8.414 877.54 

24.2 8.411 877.23 

15.2 8.452 881.50 

18.2 8.442 880.46 

19.2 8.439 880.15 

20.4 8.433 879.52 

21 8.429 879.10 

21.8 8.426 878.79 

22.6 8.419 878.06 

23.2 8.417 877.85 

24 8.411 877.23 

14.8 8.453 881.61 

17.6 8.447 880.98 

18.6 8.441 880.36 

19.8 8.435 879.73 

20.8 8.429 879.10 

21.8 8.422 878.37 

Table C.2 PG liquid density measurements 

T (°C) Lubricant mass (g) ρl (kg/m3) 

14.2 9.609 997.38 

15.8 9.604 996.44 

16.8 9.595 995.71 

17.8 9.589 995.29 

18.8 9.585 994.77 

19.8 9.573 994.36 

20.8 9.567 993.73 

21.8 9.56 993.21 

22.8 9.553 997.48 

23.6 9.549 996.96 

24.2 9.543 996.34 

14.6 9.599 995.82 

16.8 9.592 995.40 

18 9.59 994.98 

18.8 9.584 994.25 

19.6 9.579 993.73 

20.4 9.575 993.10 
 37

21.2 9.571 997.38 

21.8 9.567 996.96 

22.4 9.56 996.44 

23.2 9.556 995.82 

24.2 9.548 995.19 

15 9.6 994.77 

16 9.595 994.36 

18.2 9.588 993.63 

19.2 9.581 993.10 

20 9.578 997.38 

21 9.572 996.44 

21.8 9.566 995.71 

22.8 9.559 995.29 

23.6 9.552 994.77 

24.4 9.55 994.36 

14 9.618 993.73 

15 9.611 993.21 

15.8 9.602 997.48 

16.6 9.595 996.96 

17.4 9.591 996.34 

18.2 9.584 995.82 

19.4 9.578 995. 40 

20.4 9.571 994.98 

21.2 9.566 994.25 

22 9.562 993.73 

23 9.554 993.10 

24 9.55 997.38 

24.6 9.544 996.96 
 38

Table C.3 LP1 Liquid Density Measurements 

T (°C) Lubricant mass (g) ρl (kg/m3) 

14.2 8.89 927.19 

16.4 8.88 926.15 

17.2 8.871 925.21 

17.6 8.866 924.69 

18 8.86 924.06 

18.8 8.854 923.43 

19.8 8.849 922.91 

21.4 8.841 922.08 

22 8.838 921.77 

22.6 8.832 921.14 

23.4 8.828 920.72 

24.2 8.822 920.10 

15.2 8.875 925.62 

16.2 8.87 925.10 

16.8 8.866 924.69 

17.8 8.862 924.27 

19 8.853 923.33 

19.6 8.848 922.81 

20.4 8.846 922.61 

21.6 8.836 921.56 

22.6 8.833 921.24 

23.4 8.828 920.72 

24.2 8.823 920.20 

14.4 8.873 925.42 

15.6 8.868 924.89 

16.6 8.866 924.69 

17.6 8.859 923.96 

18.4 8.853 923.33 

19.4 8.848 922.81 

20.4 8.842 922.18 

21.6 8.835 921.45 

22.4 8.831 921.04 

23.4 8.825 920.41 

24.2 8.822 920.10 
 39

Table C.4 Density coefficients for eq. C.1 

Lubricant a0 (kg/m3

) a1 (kg m-3 K-1) 

Paraffinic 

Mineral oil 

(PARA) 

1038.76 -0.5431 

DGLF118 

(PG) 

1189.67 -0.6519 

LP1 1107.84 -0.6314 
 40

APPENDIX D: CAPILLARY RISE MEASUREMENTS 

This appendix presents capillary rise measurements for PARA, PG and LP1 at 

approximately 25 oC. Tables D.1 through D.3 provide the capillary rise height 

measurements (l) that were used to calculate the surface tension for the lubricant and the 

additive. The first column for each fluid gives the height of the liquid in the tube after it 

had been removed from the liquid pool while placing a finger over the tube opening. The 

second column for each liquid gives the rise height by subtracting off the height of the 

pool (d) from the first column measurements. The standard deviation of the mean 

measurement for this method was approximately 0.5 % of the measurement. The pool 

height was kept small so that if a 100 % error had occurred in the measurement of the 

pool depth it would contribute only approximately 10 % to the measurement of the 

capillary rise-height. 

A force balance on the column of liquid in the capillary tube was used to calculate the 

surface tension (Adamson and Gast, 1997): 

2 2

l r gl ρ rρ gl σ

∆ = ≈ (D.1) 

where the measured radius of the capillary tube (r) was 0.97 mm with a B-type estimated 

uncertainty of ± 0.03 mm. The liquid densities (ρl) measurements are given in 

Appendix C. The uncertainty of the density measurements is approximately ± 1 kg/m3

. 

The liquid-vapor (air) surface tensions as calculated from eq (D.1) for the PARA, PG and 

LP1 were 0.0306 N/m ± 0.0007 N/m, 0.0322 N/m ± 0.0007 N/m and, 0.0317 N/m ± 

0.0007 N/m, respectively. 
 41

Table D.1 Capillary rise measurements for LP1 

T (oC) h + d (mm) h (mm) ρ (kg m-3) σ (N m-1) 

24.73 29 27 919.75 0.03171 

24.73 29 27 919.75 0.03171 

24.73 29 27 919.75 0.03171 

24.72 29 27 919.75 0.03171 

24.71 29 27 919.76 0.03171 

24.63 29 27 919.81 0.03171 

Table D.2 Capillary rise measurements for PG 

T (oC) h + d (mm) h (mm) ρ (kg m-3) σ (N m-1) 

24.42 64 26 995.68 0.03306 

24.402 63.5 25.5 995.69 0.03242 

24.39 63.5 25.5 995.70 0.03242 

24.37 63.5 25.5 995.71 0.03242 

24.35 63.5 25.5 995.72 0.03242 

24.33 63.5 25.5 995.73 0.03242 

24.40 63.5 25.5 995.69 0.03242 

24.40 63.5 25.5 995.69 0.03242 

24.38 60.5 25.5 995.70 0.03242 

24.37 60.5 25.5 995.71 0.03242 

24.36 60.5 25.5 995.72 0.03242 

24.24 60.5 25.5 995.79 0.03242 

24.88 60.5 25.5 995.37 0.03241 

24.89 48 25 995.37 0.03177 

24.89 48.5 25.5 995.37 0.03241 

24.83 48 25 995.411 0.03178 

24.82 48 25 995.41 0.03178 

24.62 48 25 995.54 0.03178 

24.08 38 25 995.91 0.03179 

24.09 38 25 995.89 0.03179 

Table D.3 Capillary rise measurements for PARA 

T (oC) h + d (mm) h (mm) ρ (kg m-3) σ (N m-1) 

24.63 63.5 27.5 877.03 0.03080 

24.62 63.5 27.5 877.04 0.03080 

24.61 63.5 27.5 877.04 0.03080 

24.60 63.5 27.5 877.05 0.03080 

24.60 63.5 27 877.05 0.03024 

24.56 63.5 27 877.07 0.03024 

24.47 63.5 27 877.12 0.03024 

24.46 56 27.5 877.13 0.03080 
 42

APPENDIX E: LUBRICANT VISCOSITY MEASUREMENTS 

This appendix presents the liquid kinematic viscosity measurements for PARA, PG and 

LP1 at approximately 25 oC in Tables E.1 through E.3. Glass viscometers at the 

appropriate viscosity range were used to measure the viscosities of each lubricant. The 

B-type uncertainty of the viscometer was quoted by the manufacturer as 0.22 % of the 

measurement for the PARA lubricant and 0.29 % of the measurement for the PG 

lubricant for a 95 % confidence level. The average measured viscosity of the PARA, and 

PG lubricants, for the 95 % confidence level, was 85 μm2

/s ± 1.5 μm2/s, and 

150.3 μm2

/s ± 0.8 μm2/s, respectively. Only a single viscosity measurement of 

approximately 3800 μm2

/s was made for the LP1 lubricant because of its extremely large 

viscosity requiring over four hours. As a result, the viscosity quoted by the manufacturer 

on the MSDS of 2000 μm2/s was taken as the value for LP1. 

A model 300 viscometer with a viscosity range of 50 μm2

/s to 250 μm2/s was used. The 

calibration constant (Co) for the viscosity was a function of viscometer/liquid 

temperature: 

5 0.24317 1.6667 10 Co T− = −× (D.1) 

where T is in Celsius and Co is in μm2

/s. 

The kinematic viscosity in μm2/s was obtained by multiplying the measured efflux time 

in seconds by Co. 

Table E.1 Kinematic viscosity measurements for PARA 

T (oC) Efflux time (s) Co (μm2

/s) ν (μm2/s) 

24.648 349.55 0.242755867 84.85 

24.655 346.65 0.24275575 84.15 

24.645 352.05 0.242755917 85.46 

24.637 352.4 0.24275605 85.54 

24.635 352.1 0.242756083 85.47 

24.629 353.59 0.242756183 85.83 

Table E.2 Kinematic viscosity measurements for PG 

T (oC) Efflux time (s) Co (μm2

/s) ν (μm2/s) 

24.579 617.59 0.242757017 149.92 

24.586 599.82 0.2427569 145.61 

24.569 618.36 0.242757183 150.11 

24.562 620.5 0.2427573 150.63 

24.554 620.78 0.242757433 150.69 

24.545 619.61 0.242757583 150.41 

Table E.3 Kinematic viscosity measurements for LP1 

T (oC) Efflux time (s) Co (μm2

/s) ν (μm2/s) 

24.81 15633.25 0.242753167 3795.