EXPERIMENTAL INVESTIGATION OF EVAPORATION HEAT TRANSFER OF R-134A FLOW INSIDE A CORRUGATED TUBE

In this research, an experimental investigation has been carried out to study the heat transfer characteristics during evaporation of R-134a inside a corrugated tube. The corrugated tube has been provided with different tube inclination angles of the direction of fluid flow from horizontal, α. The Devices used in this study works based on a vapor compression refrigeration cycle. This test system includes an evaporator, which is composed of a standard corrugated tube. Heat required for evaporation of refrigerant in the evaporator is supplied by the heating element that is wrapped around it. The experiments were performed for seven different tube inclination angles, α, in a range of -90 to +90 and four mass velocities of 46, 81,110 and 136 kgm -2 s -1 for each tube inclination angle during evaporation of R-134a. The results demonstrate that the tube inclination angle, α, affects the boiling heat transfer coefficient in a significant manner. For all refrigerant mass velocities, the best performing tube is that having inclination angle of α=+90 . The effect of tube inclination angle, α, on heat-transfer coefficient, h, is more prominent at low vapor quality and low mass velocity. In the low vapor quality region the heat transfer coefficient, h, for +90 inclined tube is about 62% more than that of the -90 inclined tube.