Boiling heat transfer coefficient of R-12 alternatives in horizontal tube : small refrigerator scale

Abstract

Boiling heat transfer coefficient and pressure drop of R-12 and its alternatives which are R-134a and R-22/R-152a/R-124 (33/15/52% by mass) flowing inside smooth and grooved horizontal tubes have been carried out with the conditions similar to those in small refrigerators. The range of mass flow rates examined is between 0.0025 and 0.0125 kg/s. The data have been taken at the evaporator temperatures of  -20 to 3 ◦C and at the condenser temperatures of 40-50 ◦C. The boiling heat transfer coefficients of the refrigerants in the grooved tubes are found to be higher than those in the smooth tubes. The heat exchange correlations have also been developed. In case of the pressure drop, the two-phase friction multiplier increases linearly with Martinelli parameter and there is no effect of the tube roughness and the types of the refrigerants.