The Analysis Method And Investigation Of Thermal Performance Of Printed Circuit Heat Exchanger

With the development of the economy,the demand for energy is gradually expanding,and the world trade volume of Liquefied Natural Gas(LNG)is increasing year by year.The performance of the core component vaporizer in the regasification process of LNG before use is also particularly important.A printed circuit heat exchanger(PCHE)with excellent heat exchange performance and high efficiency is a promising choice.Many researchers have carried out experimental and numerical study on PCHE.Due to the structure of PCHE micro channel,researchers can only measure the relevant data of PCHE inlet and outlet in experiment.Limited by computational resources and experimental equipment,the numerical models of cross-flow PCHE are often simplified to a single channel and only one side of the hot or cold fluid.In order to improve the overall heat transfer performance of cross-flow PCHE,it is necessary to consider the effects of hot and cold fluid conditions on the overall flow and heat transfer characteristics of PCHE.In this study,based on the geometric structure characteristics and geometric model analysis results of cross-flow PCHE core,the core of cross-flow PCHE was divided into continuous typical layers by the thermal network analysis method and the distributed parameter model.Further,the typical layers consist continuous units.The heat transfer and flow characteristics of a single unit were analyzed.The method for analyzing the flow and heat transfer characteristics of a cross-flow PCHE is proposed.The analysis method was verified with the experimental result.Based on the above analysis method,the overall heat transfer and flow characteristics of the cross-flow PCHE core were analyzed under different thermal conditions and different hydraulic conditions.As the inlet pressure of supercritical nitrogen increases,its average convective heat transfer coefficient increases slightly and its pressure drop decreases.The non-uniformity and the effectiveness of typical layer will also be improved.As the inlet temperature of R22 increases,the heat transfer performance of supercritical nitrogen is improved,but this also results in a higher pressure drop of supercritical nitrogen.In addition,with the same inlet pressure of supercritical nitrogen,the performance evaluation standard of cross-flow PCHE increases significantly with the decrease inlet temperature of R22.When the channel diameter of the hot fluid is unchanged,the heat transfer capacity and accelerated pressure drop of the cold fluid decreases with the increasing of channel diameter of the cold fluid.The heat transfer capacity of the cold fluid will slightly decrease with the decrease of channel diameter of hot fluid.However,the increase in the heat transfer area results in an increase in the heat transfer of the hot fluid.Based on the principle of distribution uniformity,the effect of heat transfer area and inlet mass flow uniformity on the overall performance of PCHE was analyzed.With the total heat transfer area on the hot fluid side constant,the total heat transfer of the PCHE increases with the increasing of the heat transfer area of the hot fluid side near inlet of the cold fluid.Besides,the Fanning friction factor and Nusselt number on both sides also increase.Maintain uniform distribution of cold fluid inlet mass,heat transfer and total pressure drop of the PCHE increase with the mass flow distribution of the hot fluid increases along the flow direction of the cold fluid.The comprehensive thermal-hydraulic characteristics of PCHE core was improved.