Abstract:
This paper presents the heat transfer coefficients and frictional pressure drops measured during the saturated vapor condensation of R134a inside a small plate-fin heat exchanger with wavy fin surface for air-conditioning systems in aircraft. The experiments were carried out at three different saturated temperatures (34°C, 38°C and 42°C). The effects of the saturation temperature, heat flux and mass flux on the mean condensation heat transfer coefficient and core frictional pressure drop were investigated experimentally and discussed in detail. The condensation heat transfer coefficients and frictional pressure drops are compared with serrated fin surfaces obtained in previous experiments. The correlations for heat transfer coefficient and frictional pressure drop during downward flow condensation of R134a inside the plate-fin heat exchanger with wavy fin are developed based on the experimental data. Compared with the serrated fins for saturated conditions of R134a at same mass flux and saturated temperature/pressure conditions, it is found that although the wavy fins have low condensation heat transfer coefficients, its two-phase frictional pressure drop is even lower than that of the serrated fins. Therefore, if the pressure drop limitation is critical, the wavy fins can be a good selection.