非共沸混合冷媒HFC-32/HFC-125/HFC-134aおよびHFC-32/HFC-134aの水平蒸発管内熱伝達と圧力損失 [in Japanese] Heat Transfer and Pressure Drop for Flow Boiling of Non-Azeotropic Refrigerant Mixtures of HFC-32/HFC-125/HFC-134a and HFC-32/HFC-134a in Horizontal Tubes [in Japanese]
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Experiments were performed on heat transfer and pressure drop for flow boiling of two non-azeotropic refrigerant mixtures of HFC-32/HFC-125/HFC-134a and HFC-32/HFC-134a at respectively certain compositions,which are expected to be alternatives to HCFC-22,in horizontal smooth and internally,spirally grooved tubes. Almost the same local heat transfer coefficients were obtained for both the mixtures in each tube. In the smooth tube,in the region where nucleate boiling contributes substantially to the heat transfer,the heat transfer coefficients for the mixtures were reduced down to about two-thirds of the value for HCFC-22,due to the effect of a mass transfer resistance on the heat transfer,while they were approximately equal to those for HCFC-22 in the forced convection dominated region. With the grooved tube,the heat transfer was enhanced over the smooth tube,but the enhancement was smaller than that for HCFC-22. In both the tubes,frictional pressure drops for the binary mixture were generally a few to 20 percent higher than those for the ternary mixture and the pure refrigerant,corresponding to the difference in the vapor density.
Trans.JSRAE 14(1), 39-45, 1997-03-31
Japan Society of Refrigerating and Air Conditioning Engineers