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report 

fiorn the t I 

Prairie View A & M 

RESEARCH 

F 0 U N D AT I 0 N 

(HASA-CR-l85840) PLOY BOZLIfyG YITH u a 9- 279 79 -_ 

BlHAICEilElST DEVICES FOB COLD PLATE COOLANT 

CHA191EL DBSXGI Final Report (Prairie Vieu 

Agricultaral and Iecbanical Coll.) 14 p Unclas 

I 

CSCL 20D G3/34 0224580 
Contract No. NAG 9-310 

Accounting Code: 

992-15-MU-04-6A-BL-25ll-EC 

309-02-01-02-6A-BL-2511-EC 

FLOW BOILING WITH 

ENHANCEMENT DEVICES FOR 

COLD PLATE COOLANT CHANNEL DESIGN 

FINAL REPORT 

August 28, 1989 

Submitted to the 

National Aeronautics and Space Administration ("36) 

Lyndon E. Johnson Space Center 

by 

Ronald D. Boyd, Sr., Ph. D. 

Department of Mechanical Engineering 

P. 0. Box 397 

Prairie View AbM University 

Prairie View, TX 77446 

Phone: (409) 857-4811 or 4023 
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Contract No. NAG 9-310 

Accounting Code: 

992-15-MU-04-6A-BL-2Sll-EC 

309-02-01-02-6~-BL-2Sll-EC 

FLOW BOILING WITH 

ENHANCEMENT DEVICES FOR 

COLD PLATE COOLANT CHANNEL DESIGN 

FINAL REPORT 

August 28, 1989 

Prairie View CI&M University 

Department of Mechanical Engineering 

and Principal Investigator (PI) 
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FLOW BOILING WITH ENHANCEMENT 

DEVICES FOR COLD PLATE COOLANT CHCINNEL DESIGN 

Ronald D. Boyd (PI), Jerry C. Turknett, and 

Alvin Smith (Graduate Students) 

Department of Mechanical Engineering 

P. 0. Box 397 

Prairie View A8M University 

Prairie View, TX 77446 

EXECUTIVE SUMMARY 

A multi-year research program has been launched to study the 

effects of enhancement devices on flow boiling heat transfer in 

circular coolant channels, which are heated over a fraction of 

ther perimeters. The objectives of this year’s work were to (a) 

examine the variations in both the mean and local (axial, and 

circumferential) heat transfer coefficients for a circular coolant 

channel with either smooth walls or with both a twisted tape and 

spiral finned walls, and (b) initiate improvements in the present 

data reduction analysis. This continued effort is intended to 

lead to the development of fundamentally-based heat transfer 

correlations which include effects of (a) single-side heat flux, 

and (b) enhancement devite configuration. This overall program 

will set the stage for future study of heat transfer and pressure 

drop in single-side heated systems under zero-gravity conditions. 

Local (axial and circumferential) measurements C13 of the 

outside wall temperature have been made for horizontal freon-11 

flow through a 1.37 cm inside diameter coolant channel with smooth 

walls, which is heated from the top side. The exit pressure, 

inlet temperature, and mass velocity were 0.19 MPa, 24 OC, and 

0.281 Mg/mes, respectively. A preliminary data reduction model 

was used to relate the measured wall temperatures to the local 

heat transfer coefficients. For the above flow conditions, the 

preliminary results show that although both axial and I 

circumferential heat transfer coefficient (h) variations are 

important, h increased by more than 50% at the onset of nucleate 

boiling. A detail description of the work completed is contained 

in the recently completed thesis (by Jerry C. Turknett) C23, which 

was sent to both NASA Headquarters (Dr. Yvonne B. Freeman) and 

Johnson Space Center (Mr. Russ Long). Enclosed in this report is 

a summary of that work C33. 

The data reduction approach was improved slightly by I 

developing a relationship between local wall temperature I 

measurements and the mean value of h. In cases where 

circumferentially-averaged values of h were obtained, four local 

circumferential wall temperature measurements were used to obtain 
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4 

a mean value of h at each of seven axial measurement locations. 

In other cases, an approach was developed to utilize the 

twenty-eight local wall temperature measurements to obtain a 

single heat transfer coefficient, which was based on both 

circumferential and axial averaging. For the case involving 

circumferential averaging only, axial variations in the mean heat 

transfer coefficient were obtained for conditions of subcooled 

freon-11 flow boiling in a top-heated finned coolant channel with 

and without a twisted tape. For these configurations, the channel 

diameter, exit pressure, inlet temperature and mass velocity were 

1.0 cm, 0.19 MPa, 22.2 OC, and 0.21 Mg/mes, respectively. The 

results from this work indicate that in addition to enhancing the 

heat transfer, enhancement devices can reduce the axial variations 

in h. This work was summarized in a second paper t43, which is 

enclosed and which was presented at the 1989 NASB/HBCU Science and 

Engineering Research Forum. 

Rdditional work is planned C53 to (a) further refine the 

data reduction procedure for the single-side heated flow channel, 

(b) expand the experimental matrix, and (c) make comparisons of 

the experimental data with existing correlations. The expanded 

experimental matrix will include the effect of other parameters 

(subcooling, diameter, and wall configuration) on the heat 

transfer coefficient at various levels of pumping power. 
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REFERENCES 

Boyd, R. D., Sr., Turknett, J. C., and Smith, A., "Flow 

Boiling with Enhancement Devices for Cold Plate Coolant 

Channel Design," Semiannual Report, Submitted to NASA (JSC), 

Department of Mechanical Engineering, Prairie View AhM 

University Research Foundation, Prairie View, TX, (Feburary) 

1989. 

Turknett, J. C., "Forced Convection and Flow Boiling with and 

without Enhancement Devices for Top-Side-Heated Horizontal 

Channels," MS Thesis, Department of Mechanical Engineering, 

P. 0. Box 397, Prairie View AhM University, Prairie View, TX 

77446, (February) 1989. 

Boyd, R. D., Sr., and Turknett, J. C., "Forced and Flow 

Boiling with and without Enhancement Devices for Top-SideHeated Horizontal Channels," Presented at the NASA/HBCU 

Space Science and Engineering Research Forum, Alabama AhM 

University, Normal, Alabama, (March) 1989. 

Smith, A., and Boyd, R. D., Sr., "Subcooled Freon-11 Flow 

Boiling in Top-Heated Finned Coolant Channels with and 

without a Twisted Tape, "NASA/HBCU Space Science and 

Engineering Research Forum, Alabama A&M University, Normal, 

Alabama, (March) 1989. 

Boyd, R. D., Sr., "Flow Boiling with Enhancement Devices for 

Cold Plate Coolant Channel Design," Proposal, Department of , 

Mechanical Engineering, Prairie View A&M University Research 

Foundation, Prairie View, TX, (April) 1989. ~ 
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6 

DISTRIBUTION 

1. NASA Scientific 8, Technical Information Facility (2) 

P. 0. Box 8757 

Baltimore-Washington Airport 

Baltimore, MD 21240 

2. Mr. Russ Long, Technical Monitor (3) 

NASA, Lyndon E. Johnson Space Center 

Mail Code EC-5 

Houston, TX 77058 

Mark for: Contract NAG 9-310 

3. Prairie View A&M University Research Foundation 

Att: Mr. Robert Effinger 

P. 0. Box 3578 

College Station, TX 77843 

4. Dr. Ronald D. Boyd, Professor 

Department of Mechanical Engineering 

P. 0. Box 397 

Prairie View AbM University 

Prairie View, TX 77446 
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I Presented at the 1989 NASA/HBCU Research Forum 

FORCED CONVECTION CIND FLOW BOILING UITH MD WITHOUT 

ENHANCEMENT DEVICES FOR TOP-SIDE-HEATED HORIMNTL CHANNELS 

Ronald D. Boyd (PI), and Jerry C. Turknett (Graduate Student) 

Department of Mechanical Engineering 

Prairie View AhM University 

Prairie View, TX 77446 

ABSTRACT 

A three-year research program has been launched to study the 

effect of enhancement devices on flow boiling heat transfer in 

coolant channels, which are heated either from the top side or 

uniformly. Although the study will include other orientations and 

working fluids in subsequent years, the first years will involve 

studies of the variations in the local (axial and circumferential) 

and mean heat transfer coefficients in horizontal, top-heated 

coolant channels with smooth walls and internal heat transfer 

enhancement devices. Initially, the working fluid will be 

freon-11. The objectives of this fiscal year's work are to: 

(1) examine the variations in both the mean and local (axial, and 

circumferential) heat transfer coefficients for a circular coolant 

channel with either smooth walls or with both a twisted tape and 

spiral finned walls, (2) examine the effect of channel diameter 

(and the length-to-diameter aspect ratio) variations for the 

smooth wall channel, and (3) develop an improved data reduction 

anal ysi 5. 

The case of the top-heated, horizontal flow channel with 

smooth walls (1.37 cm inside diameter, and 122 cm heated length) 

has been completed. The data has been reduced using a preliminary 

analysis based on the heated hydraulic diameter. Preliminary 

cxamination of the local heat transfer coefficient variations 

indicates that there are significant axial and circumferential 

variations in the local heat transfer coefficient. However, it 

appears that the circumferential variati,on i5 more significant 

than the axial ones. In some cases, the circumferential 

variations were as much as a factor of ten. The axial variations 

rarely exceeded a factor of three. Integrated averaged heat 

transfer coefficients will be obtained after the improved data 

reduction model has been implemented. 

NOHENCLATURE 

h 

h, 

Local heat transfer coefficient, W/me OC 

Mean heat transfer coefficient due to natural convection 

between the test section and the ambient, W/mC "C 

Heat loss from the test section due to convection, W 

Heat 1055 from the test section due to radiation, W 

Radial coordinate for the data reduction model, m 

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TI Bulk temperature of the flowing fluid, OC 

T, Local measured outside wall temperature of the test 

Tsa t Saturation temperature (316 K at 0.19 flPa for freon-ll), 

T, ambient temperature, "C 

2, 2% 4xial coordinate for heated portion of the test section; 

section, OC 

"C 

in Figures 3a through 3d, Zi represents Zi, where 

ZI=20.32(i-1), cm 

Greek Letters 

P 

n 

Circumferential coordinate; see Figure la for the datum. 

In Figures 3a through 3d, I is also referred to as 

'I Ph i . I' 

Half of a full rotation or 180=.; in Figures 3a through 

3d, n is also referred to as "Pi." 

INTRODUCTION 

Space commercialization will require efficient heat transfer 

systems. The future success of many efforts will be based on our 

understanding of the behavior of two-phase flow boiling in both 

the space (zero-g or reduced-g) and earth environments. This 

three-year program is intended to focus on the following 

fundamental characteristics (e.g., nonuniform heat flux 

distribution, Marangoni effects, and single and double enhancement 

devices)of experimental flow boiling heat transfer and pressure 

drop in the earth environment 113. 

(1) examine the variations in both the mean and local (axial, and 

circumferential) heat transfer coefficients for a circular coolant 

channel with either smooth walls or with both a twisted tape and 

spiral finned walls, (2) examine the effect of channel diameter 

(length-to-diameter ratio) variations for the smooth wall channel, 

and (3) develop an improved data reduction analysis. 

In this paper, we report on forced convection and flow 

boiling of freon-11 in a smooth-wall horizontal coolant channel 

(1.37 cm inside diameter, and 122.0 cm heated length) heated from 

the top side. The inlet freon temperature was 24OC, the exit 

pressure was 0.19 MPa absolute, and the mass velocity was 0.28 

Ilg/mes. 

The objectives of the first year's efforts are to: 

EXPERIENTAL INVESTIGATION 

The reader is referred to references 11 and 23 for detail 

descriptions of the experimental flow loop, procedures, and data 

acquisition. Figure la is e schematic of the cross section of the 

heated portion of the test section [which is preceded by an 

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bo 

Domain "C"- 

Domrin "B"- 

Domrin "A"4 

'\ 

Plane of Symmetry 

(a) { 

Figure 1: Cross Section of the Heated 

Portion of the Test Section 

Control Volume of Heated 

Hydraulic Diameter Model 

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4 

upstream unheated portion for flow development]. The measured 

wall temperatures are used along with the data reduction analysis 

to determine the unknown heat transfer coefficient, h. Recently, 

a data reduction technique based on the heated hydraulic diameter 

C21 (see Figure lb) was used to reduce the experimental data. 

This approach will result in, at most, a qualitative indication of 

the local distribution of h. Work is proceeding on more viable 

data reduction approaches; e.g., finite difference for local h and 

analytical for mean h. 

In applying either model, knowledge of the fluid's bulk 

temperature must be used. An iteration scheme is used to compute 

the inside wall temperature, Tw, of the flow channel. The fluid's 

temperature is chosen based on the magnitude of the inside wall 

temperature relative to the wall temperature required to cause the 

onset to nuclueate boiling (TONm). If T, is greater than than 

Town, the fluid temperature is set equal to the saturation 

temperature. However, if the above condition is not satisfied, the 

fluid temperature is computed from the energy equation, using the 

measured inlet fluid temperature and the measured net thermal 

energy transfer to the fluid. 

RESULTS 

The results are presented for the case of forced convection 

and flow boiling with freon-11 flowing in a horizontal channel 

with smooth walls. 

The variation in the heat transfer coefficient is more 

pronounced in the circumferential direction than the axial 

direction. The heat transfer coefficients, for the single-phase 

and hypocritical regions are shown in Figure 2. The fully 

developed nucleate boiling region does not appear in the figure 

but occurs somewhere in a narrow range between P = 7n/4 and n/ 

(see Figure la for the datum for P). It is expected that the heat 

transfer coefficient in this narrow region to be greater than any 

of those shown. 

increase in the heat transfer coefficient. For P = 3n/2 and 7~14, 

the increase is due to the onset of nucleate boiling which we see 

results in more than a fifty percent increase in h. For these two 

locations we see that there is only a secondary variation in h 

with C. 

be significant. Comparisons of Figures 3a (9 = n/2), 3b (P = 

n/4), 3c (I = 7n/4) and 3d (9 = 3n/2) reveal the complex nature of 

the variations. The variation in the local heat transfer 

coefficient increases from the bottom (0 = 3n/2) to the top (P = 

n/2) of the test section at all axial locations. 4s noted 

earlier, the variation between 7n/4 and 3n/2 is small even at the 

locations where incipient nucleate boiling occurs (h = 1400 

W/mZK). It is interesting to compare the magnitude of h for the 

three regimes: (1) Single-phase (BOO W/mZK), (2) incipient 

The last two highest points on each,of the curves show an 

Both axial and circumferential variations in h are found to 
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nucleate boiling (1400 W/m2K) and, (3) film boiling (10 to 100 

W/mZK). 

If one takes time to study the relative positions of the 

curves and use the reduced wall temperature, some of the character 

of the flow is revealed (e.g., See Figure 3a). In particular, 

notice from Figure 3a that: (1) h at ZI, and Zs are almost 

identical at between 380 and 640 W, (2) h at Za is much higher 

than all values of h at other locations, and (3) in some cases 

curves are crossing one another. These observations may imply a 

slug type flow. For example, at Za the unusually large value of 

the heat transfer coefficient could be due to local cooling (slug 

flow). Contrasting the above description, Figure 3b CP = n/4) 

shows that between Ze and Zs the heat transfer coefficient 

decreases in the downstream direction. This is consistent with 

the previous observations made. That is, at P = n/4 the film 

boiling regime predominates. 

CONCLUSIONS 

Local (axial and circumferential) measurements of the outside 

wall temperature have been made for horizontal freon-11 flow (0.19 

MPa exit pressure and 24=*C inlet temperature) through a 1.37 cm 

inside diameter coolant channel with smooth walls and heated from 

1 

P 

E 

100 a0 a0 ooo 0 

Parer (W) 

Figure 2: Heat Transfer Coefficient Versus Power 

Generation and Circumferential Location at 

2 = 24 = 61.96 cm (center of the test section) 

for Top-Side-Heated Snoot9 Tubes for: 

Exit Pressure, 0.281 Mg/m s mass velocity, 

1.22 m Heated Length. 

0.19 MPa 

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d c 'E 100 -I 

p' n14 

Zl= 0.00 cm * L1r 20.32 cm * Z3= 40.64 cm 

0 Z4r W.eS cm A Z5= 01.20 cm 

Symbol Arb1 Loution 

9 Zl= 0.00 cm * L1r 20.32 cm * Z3= 40.64 cm 

0 Z4r W.eS cm A Z5= 01.20 cm 

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0 ,",""","""'",""""'~'""""I""''"'I 

100 coo WO KKK) 0 too 

Power (W) 

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400 

- _I 200 

2 

i 

5 

c 

Symbol 

* 

0 

A 

8 

Axial Location 

Zl= 000cm 

Z2= 20 3: cm 

23~ 4064 crn 

24. 6096 crr 

25s I1 28 cm 

26.101 6@ cm 

27~121 91 crn 

100 

0 600 000 l0OC 0 200 400 

Power (W) 

2 I 

Zlr 0.00 cm 

nr 10.32 cm 

4 

- 

1500 - 

lo00 - 

Y 

i 

5. 

L - 

3n12 

Zlr 40.64 cm 

Z4r 00.96 cm 

251 01.2Icm 

Io 0 m 400 coo WO (ooo 

Power (W) 

Figure 3: Heat Transfer Coefficient Versus Power And Axial 

Location at Phi = Pi/2(top), Pi/4, 7Pi/4, and 

3Pi/2(bottom) for Top-Side Heated Smooth Tubes 

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I at 0.19 MPa and 0.281 Mg/m2s. Channel 

~lr 20.32 crn 

Z3= 40.64crn 

Z4= W.06 cm 

251 01.28 cm 

26r101.W cm 27=121.92 cm 

0 

400 coo WO loot 0 too 

Power (W) 

Diameter = 1.27cm, Heated Length = 1.22m. 

6 
the top side. A preliminary data reduction model was used to 

relate the measured wall temperatures to the local heat transfer 

coefficient. Although the local temperature measurements are 

quantitative, the preliminary data reduction model results in what 

may be only qualitative local heat transfer measurements. Work is 

proceeding to evaluate and improve, if necessary, the existing 

data reduction model. 

significant axial and circumferential variations in the local heat 

transfer coefficient. However, it appears that the 

circumferential variation is more significant than the axial ones. 

The single phase heat transfer coefficient (near 900 W/meK) is 

increased by more than 50% at the onset of nucleate boiling. For 

the test performed, the circumferential heat transfer coefficient 

varied from the hypocritical to the single phase heat transfer 

regimes. This resulted tin some cases3 in a factor of ten 

increase in the local heat transfer coefficient. The axial 

variations rarely exceeded a factor of three. 

The preliminary heat transfer data indicates that there are 

ACKNOWLEDGMENTS 

The authors would like to acknowledge Richard Parish, Dr. 

Joseph atkinson, Dr. Y. Freeman, and Richard Kennedy for their 

support and assistance. The authors would also like to thank 

other NaSA personnel, both at headquarters and JSC, for their 

support . 

REFERENCES 

1. Boyd, R. D., "Flow Boiling with and without Enhancement 

Devices for Horizontal, Top-Heated, Coolant Channel5 for Cold 

Plate Coolant Channel Design fipplications, Preliminary 

Report," Department of Mechanical Engineering, Prairie View 

AbM University, Prairie View, TX, Submitted to NAS4 (JSC), 

Contract no. 9-16899 (Task+), December, 1986. 

2. Turknett, J. C., "Forced Convection and Flow Boiling with 

and without Enhancement Devices for Top-Side-Heated 

Horizontal Channels," MS Thesis, Department of Mechanical 

Engineering, Prairie View AbM University, Prairie View, TX 

(to be published). 

7