Evaporation heat transfer and pressure drop characteristics of r-134a in the oblong shell and plate heat exchanger

Abstract

The evaporation heat transfer coefficient hr and frictional pressure drop Δpf of refrigerant R-134a flowing in the oblong shell and plate heat exchanger were investigated experimentally in this study. Four vertical counterflow channels were formed in the oblong shell and plate heat exchanger by four plates of geometry with a corrugated sinusoid shape of a 45° chevron angle. Upflow of refrigerant R-134a boils in two channels receiving heat from downflow of hot water in other channels. The effects of the refrigerant mass flux, average heat flux, refrigerant saturation temperature and vapor quality of R-134a were explored in detail. Similar to the case of a plate heat exchanger, even at a very low Reynolds number, the flow in the oblong shell and plate heat exchanger remains turbulent. The results indicate that the evaporation heat transfer coefficient hr and pressure drop Δpf increase with the vapor quality. A rise in the refrigerant mass flux causes an increase in the hr and Δpf. But the effect of the average heat flux does not show significant effect on the hr and Δpf. Finally, at a higher saturation temperature, both the hr and Δpf are found to be lower. The empirical correlations are also provided for the measured heat transfer coefficient and pressure drop in terms of the Nusselt number and friction factor.