scholarly journals BOILING AND CONDENSATION HEAT TRANSFER COEFFICIENTS FOR A DOWTHERM-A CHARGED HEAT PIPE HEAT EXCHANGER

2013 ◽  
Vol 4 (2) ◽  
Author(s):  
Robert T. Dobson ◽  
Ryno Laubscher
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pipe ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Heat

Average Boiling and Condensation Heat Transfer Coefficients of the Zeotropic Refrigerant Mixture R22/R142b in a Coaxial Tube-in-Tube Heat Exchanger

1999 ◽  
Vol 122 (1) ◽  
pp. 186-188 ◽  
Author(s):  
J. P. Meyer ◽  
J. M. Bukasa ◽  
S. A. Kebonte
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pumps ◽  
Hot Water ◽  
Outer Tube ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Tube Heat Exchanger ◽  
Heat Transfer Coefficients ◽  
Coaxial Tube

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]

Convection Condensation Heat Transfer of Steam-Air Mixture With Heat Pipe Heat Exchanger

2013 ◽  
Vol 35 (6-8) ◽  
pp. 600-609 ◽  
Author(s):  
Xuehu Ma ◽  
Zhong Lan ◽  
Wei Xu ◽  
Chongfeng Zhang ◽  
Zheng Fang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pipe ◽  
Condensation Heat Transfer ◽  
Pipe Heat

Measurement and Modeling of Condensation Heat Transfer Coefficients in Circular Microchannels

2006 ◽  
Vol 128 (10) ◽  
pp. 1050-1059 ◽  
Author(s):  
Todd M. Bandhauer ◽  
Akhil Agarwal ◽  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Heat Transfer Model ◽  
Condensation Heat Transfer ◽  
Low Flow ◽  
Transfer Model ◽  
Shear Stresses ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Circular Microchannels

A model for predicting heat transfer during condensation of refrigerant R134a in horizontal microchannels is presented. The thermal amplification technique is used to measure condensation heat transfer coefficients accurately over small increments of refrigerant quality across the vapor-liquid dome (0<x<1). A combination of a high flow rate closed loop primary coolant and a low flow rate open loop secondary coolant ensures the accurate measurement of the small heat duties in these microchannels and the deduction of condensation heat transfer coefficients from measured UA values. Measurements were conducted for three circular microchannels (0.506<Dh<1.524mm) over the mass flux range 150<G<750kg∕m2s. Results from previous work by the authors on condensation flow mechanisms in microchannel geometries were used to interpret the results based on the applicable flow regimes. The heat transfer model is based on the approach originally developed by Traviss, D. P., Rohsenow, W. M., and Baron, A. B., 1973, “Forced-Convection Condensation Inside Tubes: A Heat Transfer Equation For Condenser Design,” ASHRAE Trans., 79(1), pp. 157–165 and Moser, K. W., Webb, R. L., and Na, B., 1998, “A New Equivalent Reynolds Number Model for Condensation in Smooth Tubes,” ASME, J. Heat Transfer, 120(2), pp. 410–417. The multiple-flow-regime model of Garimella, S., Agarwal, A., and Killion, J. D., 2005, “Condensation Pressure Drop in Circular Microchannels,” Heat Transfer Eng., 26(3), pp. 1–8 for predicting condensation pressure drops in microchannels is used to predict the pertinent interfacial shear stresses required in this heat transfer model. The resulting heat transfer model predicts 86% of the data within ±20%.

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