TUBE-SIDE TWO-PHASE HEAT TRANSFER COEFFICIENTS OF REFRIGERANT HFC-134a FLOWING THROUGH A FIN-AND-TUBE EVAPORATOR

Abstract

In the present study, the two-phase heat transfer coefficient characteristics of HFC-134a, evaporating inside a plate fin-and-tube evaporator with plain fin geometry, are experimentally investigated. The experimental apparatus consists essentially of a well modified vapour compression refrigeration system. Evaporator and condenser are made from aluminium plate finned, copper tube. In addition to the loop components, a full set of instruments for measuring temperature, pressure and flow rate of the refrigerant and the air are installed at the important points in the circuit. The test runs are done at average saturated refrigerant temperatures ranging between 4.0 and 9.0 °C for evaporation and ranging between 39.0 and 46.0 ° C for condensation. The refrigerant mass flow rates are between 7.6 x 10 -3 and 9.0 x × 10 -3 kg/s. The volumetric flow rate of air passing through the evaporator ranges between 0.25 and 0.5 m 3 /s and between 0.7 and 1.25 m 3 /s for the condenser. The average amount of heat exchanged between the refrigerant-side and air-side is between 1270 and 1770 W for the evaporator and between 1740 and 2200 W for the condenser. The experimental data obtained from the present study together with various relevant parameters from literature are used to determine the tube-side evaporation heat transfer coefficients. The results from the present study are compared with those calculated from correlations reported in literature. Moreover, a new correlation based only on the data gathered during this work is proposed for practical application.