Numerical Study On Thermal-Hydraulic Performance Of Printed Circuit Heat Exchanger And Micro-tube Heat Exchanger

Compared with the traditional shell and tube heat exchangers,the compact heat exchanger with supercritical carbon dioxide as the working medium can effectively improve the efficiency of thermal cycle and reduce the size of components.The Compact heat exchangers investigated are.divided into two types namely Printed Circuit Heat Exchanger(PCHE)and Micro-tube Heat Exchanger.In order to analyze the thermal hydraulic performance of the compact heat exchanger,based on the thermo-physical characteristics of the supercritical carbon dioxide as working fluid,the main features of the Printed Circuit Heat Exchanger and Micro-tube Heat Exchanger have been investigated.Three types Printed Circuit Heat Exchanger and Micro-tube Heat Exchanger are studied and compared in terms of dimensionless numbers with flow being in Laminar regime.The numerical simulations have carried out using Computational Fluid Dynamics(CFD)method.The channel types for PCHE are Zigzag channel with 15 angle,Wavy channel and Airfoil Fin(AFF)channel.The results show that the Zigzag channel has better heat transfer performance than the Wavy channel and the AFF channel.In case of pressure losses,the AFF channel has better performance than the Zigzag channel and Wavy channel.According to this analysis,the straight channels with different fin types should further be investigated.In Micro-tube Heat exchanger,three models have been investigated with varying micro-tube inner diameter.The diameter studied are 0.8mm,1 mm and 1.2mm with outer diameter of 2mm.The results show that the heat transfer is improved with the increase in size of micro-tube.On the other hand,the pressure losses have also increased with the increase of micro-tube inner diameter.At the same time,considering the effect of heat transfer and pressure losses,the area goodness factor(AGF)is introduced as a measure index.The results show that the model with micro-tube diameter external diameter of 2mm and the inner diameter of 0.8mm has the best comprehensive performance.In this study,the thermal-hydraulic performance of compact heat exchangers has been investigated using supercritical carbon dioxide.The recommendations have been made for study of turbulent flow regime and employment of experimental setup.