Two-phase flow heat transfer of R-134a in microtubes |
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Authors: | Yun Wook Hwang Min Soo Kim |
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Affiliation: | (1) Energy Research Institute of Shandong Academy of Sciences, Jinan, 250014, China;(2) College of Power Engineering, Nanjing Normal University, Nanjing, 210042, China |
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Abstract: | The characteristics of the two-phase flow heat transfer of R-134a in microtubes with inner diameters of 430 μm and 792 μm
were experimentally investigated. The effect of the heat flux on the heat transfer coefficient for microtubes was significant
before the transition quality. The boiling number expressed the interrelation between the heat flux and the mass about the
heat transfer coefficients. The smaller microtube had greater heat transfer coefficients; the average heat transfer coefficient
for the tube A (D
i
= 430 μm) was 47.0% greater than that for the tube B (D
i
= 792 μm) at G = 370 kg/m2·s and q″ = 20 kW·m2. A new correlation for the evaporative heat transfer coefficients in microtubes was developed by considering the following
factors: the laminar flow heat transfer coefficient of liquid-phase flow, the enhancement factor of the convective heat transfer,
and the nucleate boiling correction factor. The correlation developed in present study predicted the experimental heat transfer
coefficients within an absolute average deviation of 8.4%. |
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Keywords: | |
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