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RESEARCH PAPERS: Micro/Nanoscale Heat Transfer

Measurement and Modeling of Condensation Heat Transfer Coefficients in Circular Microchannels

[+] Author and Article Information
Todd M. Bandhauer

 Modine Manufacturing Company, Racine, WI 53403

Akhil Agarwal

GWW School of Mechanical Engineering,  Georgia Institute of Technology, Atlanta, GA 30332-0405

Srinivas Garimella

GWW School of Mechanical Engineering,  Georgia Institute of Technology, Atlanta, GA 30332-0405srinivas.garimella@me.gatech.edu

J. Heat Transfer 128(10), 1050-1059 (Mar 07, 2006) (10 pages) doi:10.1115/1.2345427 History: Received June 17, 2005; Revised March 07, 2006

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<750kgm2s. 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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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the test facility

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Figure 2

Test section and tubes tested

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Figure 3

Representative heat transfer coefficients and uncertainties, Dh=0.761mm

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Figure 4

Measured heat transfer coefficients

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Figure 5

Comparison of data from present study with two-phase-multiplier based correlations

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Figure 6

Comparison of data from present study with predictions of homogeneous flow models

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Figure 7

Comparison of data from present study with boundary layer annular flow treatments

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Figure 8

Comparison of measured and predicted heat transfer coefficients from the present study

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Figure 9

Trends predicted by current model

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