Experimental investigation on the flow boiling of R134a in a plate heat exchanger with mini-wavy corrugations

Abstract

As a common component in various applications, the two-phase heat transfer of plate heat exchanger has been frequently studied. However, further investigations are still required on the flow pattern, especially for those with new plate structure brought with the emergence of new applications. This study presented an experimental investigation on the flow boiling of R134a in a plate heat exchanger with mini-wavy corrugations designed for thermal management system of electric vehicle (EV). The flow pattern transitions in the test section were captured and discussed, meanwhile the effects of vapor quality and mass flux on the variation of heat transfer coefficient (HTC) were analyzed. Based on the observation, the two-phase flow pattern developed from pulsating film flow, then rough stream flow and finally to thin stream flow with the increase of vapor quality. The flow pattern map was determined with the superficial momentum of the liquid and vapor phase refrigerant, while the empirical correlations were developed based on two-phase Weber number to predict the transitions between the flow patterns. The HTC showed an intermediate increase firstly under low vapor qualities, and rapidly decreased after reaching the peak value at the vapor quality of 0.45-0.6. In addition, the experimental data were compared with the present correlations, and a new Nu correlation was developed considering the transitions of flow patterns, showing an optimal prediction on the experimental data with the mean absolute error of 11.3%.