Condensing Heat Transfer Characteristics of HFC-134a and CFC-12 Inside a Smooth Tube in Low Mass Velocity Range

Abstract

Condensing heat transfer coefficients of HFC-134a and CFC-12 were measured inside a horizontal and a vertical smooth tub with an inner diameter of 4.35mm. The mass velocity of refrigerant ranged from 60 to 170 kg/(m²s) and the saturation temperature was about 450°C.
The results obtained are as follows ; (1) According to the difference in flow directions, condensing heat transfer coefficients in low mass velocity range (below 100 kg / (m²s)) were ranked as follows ;
horizontal›vertical upward›vertical downward.
(2) Condensing heat transfer coefficient of HFC-134a was 15-20% higher than that of CFC-12 with both horizontal and vertical tubes.