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Research Papers: Evaporation, Boiling, and Condensation

Flow Boiling of R134a in Circular Microtubes—Part I: Study of Heat Transfer Characteristics

[+] Author and Article Information
Saptarshi Basu, Sidy Ndao, Yoav Peles

Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180

Gregory J. Michna

Department of Mechanical Engineering, South Dakota State University, Brookings, SD 57007

Michael K. Jensen1

Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180jensem@rpi.edu

1

Corresponding author.

J. Heat Transfer 133(5), 051502 (Feb 03, 2011) (9 pages) doi:10.1115/1.4003159 History: Received April 13, 2010; Revised December 01, 2010; Published February 03, 2011; Online February 03, 2011

An experimental study of two-phase heat transfer coefficients was carried out using R134a in uniformly heated horizontal circular microtubes with diameters from 0.50 mm to 1.60 mm over a range of mass fluxes, heat fluxes, saturation pressures, and vapor qualities. Heat transfer coefficients increased with increasing heat flux and saturation pressure but were independent of mass flux. The effects of vapor quality on heat transfer coefficients were less pronounced and varied depending on the quality. The data were compared with seven flow boiling correlations. None of the correlations predicted the experimental data very well, although they generally predicted the correct trends within limits of experimental error. A correlation was developed, which predicted the heat transfer coefficients with a mean average error of 29%. 80% of the data points were within the ±30% error limit.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 8

Effect of saturation pressure on heat transfer coefficients for flow boiling of R134a for din=0.50 mm, G=1500 kg/m2 s, q″=165 kW/m2, and ΔTsubcooling=5°C

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Figure 7

Effect of mass flux on heat transfer coefficients for flow boiling of R134a for din=0.96 mm at Psat=890 kPa, q″=90 kW/m2, and ΔTsubcooling=5°C

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Figure 6

Effect of heat flux and mass flux on heat transfer coefficients for flow boiling of R134a for din=0.50 mm at Psat=890 kPa and ΔTsubcooling=5°C

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Figure 5

Boiling curve for the three test sections at Psat=890 kPa, G=1000 kg/m2 s, and ΔTsubcooling=5°C

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Figure 4

Boiling curve din=0.96 mm at Psat=1160 kPa and ΔTsubcooling=20°C

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Figure 3

Nu versus Re for single-phase flow of R134a

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Figure 2

Schematic of the test section apparatus

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Figure 1

Description of experimental apparatus

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Figure 9

Effect of equilibrium vapor quality on heat transfer coefficients for flow boiling of R134a for din=0.50 mm, Psat=1160 kPa, and ΔTsubcooling=5°C

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Figure 10

Effect of equilibrium vapor quality on heat transfer coefficients for flow boiling of R134a for din=1.60 mm, Psat=1160 kPa, and ΔTsubcooling=5°C

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Figure 11

Comparison of experimental trends with the correlations

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Figure 12

Comparison of experimental data with the new correlation

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