This study presents a model for the two-phase flow and heat transfer in the closed loop, two-phase thermosyphon (CLTPT) involving co-current natural circulation. The focus is on CLTPTs for electronics cooling that exhibit complex two-phase flow patterns due to the closed loop geometry and small tube size. The present model is based on mass, momentum, and energy balances in the evaporator, rising tube, condenser, and the falling tube. The homogeneous two-phase flow model is used to evaluate the friction pressure drop of the two-phase flow imposed by the available gravitational head through the loop. The saturation temperature dictates both the heat source (chip) temperature and the condenser heat rejection capacity. Thermodynamic constraints are applied to model the saturation temperature, which also depends upon the local heat transfer coefficient and the two-phase flow patterns inside the condenser. The boiling characteristics of the enhanced structure are used to predict the chip temperature. The model is compared with experimental data for dielectric working fluid PF-5060 and is in general agreement with the observed trends. The degradation of condensation heat transfer coefficient due to diminished vapor convective effects, and the presence of subcooled liquid in the condenser are expected to cause higher thermal resistance at low heat fluxes. The local condensation heat transfer coefficient is a major area of uncertainty.

Issue Section:
Two-Phase Flow and Heat Transfer
Keywords:
packaging, cooling, heat exchangers, pipe flow, two-phase flow, thermodynamic properties, undercooling, convection, Cooling, Electronics, Heat Transfer, Thermosyphons, Two-Phase
Topics:
Condensation, Condensers (steam plant), Heat transfer, Pressure, Temperature, Two-phase flow, Vapors, Flow (Dynamics), Heat, Pressure drop, Boiling, Heat flux, Subcooling
1.
Yuan, L., Joshi, Y. K., and Nakayama, W., 2001, “Effect of Condenser Location and Tubing Length on the Performance of a Compact Two-Phase Thermosyphon,” Proc. 2001 ASME International Mechanical Engineering Conference and Exposition, Session on Heat Pipes and Multiphase Heat Transfer in Electronic System, November 11–16, New York, NY.
2.
El-Genk
,
M. S.
, and
Saber
,
H. H.
,
1998
, “
Heat Transfer Correlations for Liquid Film in the Evaporator of Enclosed, Gravity-Assisted Thermosyphons
,”
ASME J. Heat Transfer
,
120
, pp.
477
–
484
.
3.
Harley
,
C.
, and
Faghri
,
A.
,
1994
, “
Complete Transient Two-Dimensional Analysis of Two-Phase Closed Thermosyphons Including the Falling Condensate Film
,”
ASME J. Heat Transfer
,
116
, pp.
418
–
426
.
4.
Zuo
,
Z. J.
, and
Gunnerson
,
F. S.
,
1994
, “
Numerical Modeling of the Steady-state Two-Phase Closed Thermosyphon
,”
Int. J. Heat Mass Transf.
,
37
(
17
), pp.
2715
–
2722
.
5.
El-Genk
,
M. S.
, and
Saber
,
H. H.
,
1999
, “
Determination of Operation Envelopes for Closed, Two-phase Thermosyphons
,”
Int. J. Heat Mass Transf.
,
42
, pp.
889
–
903
.
6.
Vincent
,
C. C. J.
, and
Kok
,
J. B. W.
,
1992
, “
Investigation of the Overall Transient Performance of the Industrial Two-Phase Closed Loop Thermosyphon
,”
Int. J. Heat Mass Transf.
,
35
, No.
6
, pp.
1419
–
1426
.
7.
Wang
,
J. C. Y.
, and
Ma
,
Y.
,
1991
, “
Condensation Heat Transfer Inside Vertical and Inclined Thermosyphons
,”
ASME J. Heat Transfer
,
113
, pp.
777
–
780
.
8.
Carey, Van P., 1992, Liquid-Vapor Phase-change Phenomena, Hemisphere Publishing Corporation.
9.
Cammarata, G., Fichera, A., Froghieri, M., Misale, M., and Xibilia, M. G., 1999, “A New Modeling Methodology of Natural Circulation Loop for Stability Analysis,” Single and Two-Phase Natural Circulation, Proceedings of EUROTHERM SEMINAR No. 63, September 6–8, 1999, Genoa, Italy.
10.
Tengblad, N., 1996, “Cooling of Electronic Components with Closed Loop Two-Phase Thermosiphons,” Engineering Licentiate Thesis, The Royal Institute of Technology, Stockholm, Sweden, pp. 17–50, Chap. 3.
11.
McAdams
,
W. H.
,
Woods
,
W. K.
, and
Heroman
, Jr.,
L. C.
,
1942
, “
Vaporization Inside Horizontal Tubes—II—Benzene-Oil Mixtures
,”
Trans. ASME
,
64
, p.
193
193
.
12.
Collier, J. G., 1981, Convective Boiling and Condensation, Second Edition, pp. 30–34. McGraw-Hill Book Company (UK) Ltd.
13.
Bar-Cohen
,
A.
, and
Rohsenow
,
W. M.
,
1984
, “
Thermally Optimum Spacing of Vertical Natural Convection Cooled, Parallel Plates
,”
ASME J. Heat Transfer
,
106
, p.
116
116
.
14.
Ananiev, E. P., Boyko, L. D., and Kruzhilin, G. N., 1961, “Heat Transfer in the Presence of Steam Condensation in a Horizontal Tube,” Proc. 1st Int. Heat Transfer Conf., part II, p. 290.
15.
Engineering Equation Solver (EES), F-Chart Software, www.fChart.com.
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