An improved zigzag-type printed circuit heat exchanger for supercritical CO2 Brayton cycles

Abstract

Printed Circuit Heat Exchanger (PCHE) is a kind of high performance compact heat exchanger. In this study, a zigzag-type PCHE with improved flow passage arrangement, i.e., cellular arrangement, is proposed considering the fin efficiency enhancement. And the new PCHE with channels cellular arrangement coupled with supercritical CO2 (sCO2) Brayton cycle is investigated numerically. Flow and heat transfer characteristics in cellular zigzag-type PCHE is compared with the traditional flat-plate zigzag-type PCHE. Results show that the structure of the flow field in zigzag channels promotes the mixing between the fluid near the wall and the bulk fluid. The process of mixing is beneficial to intensify the convective heat transfer capacity. A pronounced increase of frictional pressure drop is also observed in zigzag channels when compared with straight channel. The overall heat transfer coefficient of cellular zigzag-type PCHE is about 8.6% higher than that of traditional flat-plate zigzag-type PCHE with the same operating condition in this study. The reason for heat transfer enhancement in cellular zigzag-type PCHE is that the secondary heat transfer surface in flat-plate zigzag-type PCHE is transferred to be the primary heat transfer surface, which is highly efficient heat transfer surface. As just alternating the hot and cold channels in cellular arrangement when compared with traditional arrangement, the pressure drop does not increase much while heat transfer is increased, so thermal performance is improved in cellular zigzag-type PCHE. As a result, the fixed investment/operation cost of cellular zigzag-type PCHE can be decreased. In this paper, a possible manufacture design of the arrangement improved PCHE is also achieved with turn-over channels.