Abstract

Average boiling and condensation heat transfer coefficients were determined experimentally for a coaxial tube-in-tube heat exchanger used in hot water heat pumps. During manufacturing, the heat exchanger geometry used for the experiments changed from round tubes to elliptical tubes as no spacers were used to keep the inner tube from touching the outer tube. The refrigerant used was two different mixtures of R22 with R142b in mass ratios of 80 percent/20 percent and 60 percent/40 percent. The results were compared to theoretical results for straight tubes. It was concluded that the theoretical modes do not predict the heat transfer coefficients very well in coaxial tube-in-tube heat exchangers where the annulus touches the inside of the outer tube. [S0022-1481(00)01001-X]

Issue Section:
Technical Notes
Keywords:
heat transfer, boiling, condensation, refrigeration, heat exchangers, Experimental Heat Transfer, Boiling, Condensation, Refrigerants, R22, R142b, Coaxial, Tube-in-Tube, Heat Exchanger
Topics:
Boiling, Condensation, Heat exchangers, Heat transfer coefficients, Refrigerants, Heat transfer, Hot water, Heat pumps
1.
Kruse, H. H., and Tiedemann, T., 1997, “Experience With HC Refrigerants and Projections for Future Applications, Current and Projected Use of Refrigerants in Europe,” Refrigerants for the 21st Century, ASHRAE/NIST Refrigerants Conference, Gaithersburg, MD, pp. 44–56.
2.
Meyer
,
J. P.
, and
Greyvenstein
,
G. P.
1991
, “
Hot Water for Homes in South Africa
,”
Energy Int. J.
16
, pp.
1039
–
1044
.
3.
Meyer
,
J. P.
and
Greyvenstein
,
G. P.
1992
, “
Hot Water for Large Residential Units, Hospitals and Laundries with Heat Pumps in South Africa: A Techno-economic Analysis
,”
Energy Convers. Manage.
33
, No.
2
. pp.
135
–
143
.
4.
Smit
,
F. J.
and
Meyer
,
J. P.
,
1998
, “
Investigation of the Potential Effect of Zeotropic Refrigerant Mixture on Performance of a Hot-Water Heat Pump
,”
ASHRAE Trans.
,
104
, pp.
387
–
394
.
5.
Johannsen, A. F. B., 1992, “Potential of Non-azeotropic Refrigerant Mixtures for Water-Heating Heat Pumps in South Africa,” Department of Mineral and Energy Affairs, Pretoria, South Africa, Report No. ED 8807.
6.
Smit, F. J., 1996, “The Influence of a Non-azeotropic Refrigerant Mixture on the Performance of a Hot-Water Heat Pump,” M. Eng. dissertation, Rand Afrikaans University, Johannesburg, South Africa.
7.
Kebonte, S. A., 1999, “Condensation Heat Transfer and Pressure Drop Coefficients of R22/R142b in a Water Cooled Helically Coiled Tube-in-Tube Heat Exchanger,” M. Eng. dissertation, Rand Afrikaans University, Johannesburg, South Africa.
8.
Bukasa, J. M., 1999, “Average Boiling Heat Transfer and Pressure Drop Coefficients of R22/R142b in a Helically Coiled Water Heated Tube-in-Tube Heat exchanger,” M. Eng. dissertation, Rand Afrikaans, University, Johannesburg, South Africa.
9.
Schlager
,
L. M.
,
Pate
,
M. B.
, and
Bergles
,
A. E.
,
1990
, “
Evaporation and Condensation Heat Transfer and Pressure Drop in Horizontal, 12.7-mm Microfin Tubes with Refrigerant 22
,”
ASME J. Heat Transfer
112
, pp.
1041
–
1047
.
10.
Kline
,
S. J.
, and
McClintock
,
F. A.
1953
, “
Describing Uncertainties in Single Sample Experiments
,”
Mech. Eng.
,
75
, pp.
3
–
8
.
11.
Akers
,
W. W.
,
Beans
,
H. A.
, and
Crosser
,
O. K.
1959
, “
Condensation Heat Transfer Within Horizontal Tubes
,”
Chem. Eng. Prog. Symp. Ser.
,
55
, No.
29
pp.
171
–
176
.
12.
Cavallini, A., and Zecchin, R. A., 1974 “A Dimensionless Correlation for Heat Transfer in Forced Convention Condensation,” 6th International Heat Transfer Congress, Tokyo, Japan, Vol. 3, pp. 309–313.
13.
Travis
,
D. P.
,
Rohsenov
,
W. M.
, and
Baron
,
A. B.
,
1973
, “
Forced Convection Condensation Inside Tubes: A Heat Transfer Equation for Condenser Design
,”
ASHRAE Trans.
,
79
, pp.
157
–
165
.
14.
Azer
,
N. Z.
,
Abis
,
L. V.
, and
Soliman
,
H. M.
1972
, “
Local Heat Transfer Coefficient During Forced Convection Condensation Inside Horizontal Tube
,”
ASHRAE Trans.
,
77
, Part 1, pp.
182
–
201
.
15.
Jung
,
D. S.
,
McLinden
,
M.
,
Radermacher
,
R.
, and
Didion
,
D.
,
1989
, “
Horizontal Flow Boiling Heat Transfer Experiments With a Mixture of R22/R114
,”
Int. J. Heat Mass Transf.
,
32
, pp.
131
–
145
.
16.
Murata
,
K.
, and
Hashizume
,
K.
1993
, “
Forced Convective Boiling of Non-Azeotropic Refrigerant Mixtures Inside Tubes
,”
J. Heat Transfer
,
115
, pp.
680
–
688
.
17.
Thome
,
J. R.
1996
, “
Boiling of New Refrigerants: A State of the Art Review
,”
Int. J. Refrig.
,
19
, pp.
435
–
457
.
Copyright © 2000
 by ASME
You do not currently have access to this content.