Optimization of Grid Structure for Supercritical CO2 Plate Diffusion Welded Rectangular Micro-channel Heat Exchanger
In order to improve the comprehensive flow and heat transfer performance of the printed circuit heat exchanger(PCHE)in the supercritical carbon dioxide(S-CO2)Brayton cycle system,a mathematic-physical model of the heat exchange unit with hot and cold channels is established,based on a new-type rectangular section PCHE manufactured by full etching technology in this paper.The influence mechanism and law of the grid spacing in the channels on the flow and heat transfer characteristics of S-CO2 under different operation conditions are numerically investigated.The results show that the flow velocity of S-CO2 in hot channels with different grid spacings decreases gradually along the channel,while that in cold channels increases gradually along the channel.At the same time,the flow frictional resistance coefficient(f)and Nusselt number(Nu)in hot and cold channels are both increased with the increasing grid spacing.Besides,f and Nu in cold channel are always larger than those in hot channel.When the grid spacing is 5.97 mm,the rectangular section channel has relatively optimal comprehensive performance,which can achieve enhanced heat transfer with small resistance loss.The research results can provide theoretical and data support for the performance improvement and structure optimization of rectangular section PCHE manufactured by full etching technology.