Condensation flow visualization, heat transfer, and pressure drop in printed circuit heat exchangers with straight and wavy microchannels

Abstract

This study experimentally investigated the condensation flow visualization, heat transfer, and pressure drop characteristics of R1234ze(E) and R32 in printed circuit heat exchangers (PCHEs) with straight and wavy microchannel geometries. The effects of the microchannel geometries and refrigerants on the condensation flow, heat transfer, and pressure drop characteristics were investigated. Three flow patterns, namely, the nondisturbance annular, annular, and plug flows, were observed in the straight microchannels, whereas only annular and plug flows were observed in the wavy microchannel. A thin liquid film was observed to form on the inner arc of the wavy microchannel in the plug flow region. The overall heat transfer coefficient and pressure drop of the PCHE with the wavy microchannel were, respectively, 11% and 18% higher than those of the PCHE. The overall heat transfer coefficient and pressure drop of R1234ze(E) were 29% lower and 42% higher, respectively, than those of R32.