Research On The Flow And Heat Transfer Performance Of Heat Exchangers For Silicon Carbide Printed Circuit Boards

The supercritical carbon dioxide(S-CO2)Brayton cycle is a power generation cycle system that has received much attention in recent years.The printed circuit board heat exchanger(PCHE)is the core equipment of the Brayton cycle,and the flow and heat transfer performance of the silicon carbide PCHE has been studied in order to investigate the laws of the new silicon carbide PCHE currently used.In this paper,a combination of surface response and computational fluid dynamics is used to optimize the development of Z-shaped and wing-shaped silicon carbide PCHEs,which are considered as high and low temperature heat exchangers,respectively.The effects of structural dimensions and operating parameters are taken into account,and the surface response analysis is performed using the Fanning friction coefficient and Nussle number in the cold fluid channel as response values,and the main research contents of the paper are as follows:(1)Determine the level and range of each unique variable in the surface response,determine the FLUENT solution process,establish the physical model,determine the control equations,turbulence model,fit the materiality polynomial,complete the mesh division and irrelevance verification,and perform FLUENT simulation according to the corresponding table of the surface.(2)The flow and heat transfer characteristics of the Z-shaped silicon carbide PCHE as a high-temperature heat exchanger and low-temperature heat exchanger were analyzed by the surface response method.Characteristics of the influence of the significant order from large to small is the channel bending angle > channel diameter > mass flow rate > hot fluid inlet temperature > cold fluid inlet temperature > cold fluid pressure.For the heat transfer performance of Z-type silicon carbide PCHE as a high-temperature heat exchanger,the significance of the influence of each factor from large to small is channel diameter > mass flow rate > channel bending angle >hot fluid inlet temperature > cold fluid pressure > cold fluid inlet temperature,as a low-temperature heat exchanger the significance of the influence from large to small is channel diameter > mass flow rate > channel bending angle > cold fluid inlet temperature > hot fluid inlet temperature > cold fluid pressure.(3)The flow and heat transfer characteristics of the wing-type silicon carbide PCHE as high-temperature heat exchanger and low-temperature heat exchanger were analyzed by the surface response method,and the significance of each factor on the flow when the wing-type silicon carbide PCHE was used as high-temperature heat exchanger and low-temperature heat exchanger was from large to small,and the significance of each factor on the heat transfer performance was from large to small,namely,airfoil staggering distance > mass flow rate > hot fluid inlet temperature >cold fluid inlet temperature.Airfoil staggering distance > mass flow rate > hot fluid inlet temperature > cold fluid inlet temperature;airfoil PCHE is a discontinuous channel,fluid hitting the leading edge of the airfoil is separated into two streams of fluid,fluid flowing against the streamlined outer surface of the airfoil,when it passes the widest point of the airfoil,there is a transverse flow component returning to the airfoil wall,and finally mixed in the airfoil-free part,this flow characteristic also makes the airfoil staggering distance increase when This flow characteristic also makes the airfoil intersection distance increase,the airfoil-free area decreases,the shunt at the top of the airfoil and the mixing at the end of the airfoil proceed simultaneously,and the perturbation of the flow intensifies,thus causing a drastic effect on the flow and heat transfer in the airfoil-type silicon carbide PCHE channel.(4)Using the surface response software Design Expert,the optimal flow conditions and the optimal heat transfer conditions for the Z-shaped and wing-type silicon carbide PCHEs as high-temperature and low-temperature heat return heaters are simulated according to the model,respectively.(5)In order to maintain low pressure drop loss with high heat transfer,the PEC(Performance Evaluation Criteria)formula,which is closest to the actual operating conditions considering economic efficiency,is derived based on the relationship between power consumption and velocity in a cubic proportion,and the optimal conditions for the Z-shaped PCHE as a high-temperature heat exchanger are cold fluid pressure 20.181 MPa,cold fluid inlet temperature 545.843 K,hot fluid inlet temperature 800.001 K,channel bend angle 15.003°,diameter 1.8mm,mass flow rate 350kg/m2-s,as a low temperature heat exchanger optimal conditions for cold fluid pressure 20.292 MPa,cold fluid inlet temperature 340 K,hot fluid inlet temperature 564.37 K,channel bending angle 15°,diameter 1.8mm,mass flow rate350kg/m2-s;wing type PCHE as a high temperature heat exchanger,the optimal conditions for mass flow rate 0.003kg/s,cold fluid inlet temperature 540.005 K,thermal fluid inlet temperature 800 K,airfoil staggering distance 3.88 mm,low temperature heat exchanger optimal conditions for mass flow rate 0.003 kg / s,cold fluid inlet temperature 340.008 K,thermal fluid inlet temperature 550 K,airfoil staggering distance 3.779 mm.