Simulation And Optimization Of Microchannel Heat Exchanger And Phase Change Cooling Storage System

Phase change cold storage technology is an effective way to realize heat dissipation and temperature control of equipment.The application of microchannel heat exchanger in phase change cold storage system conforms to the development trend of miniaturization and high power of equipment,and has been gradually applied in various systems.At present,simulation technology has been widely used in traditional refrigeration devices,but for the refrigeration cycle of phase change refrigeration storage system with microchannel heat transfer,the corresponding simulation research is not mature enough.Therefore,it is necessary to establish the corresponding mathematical model and study the influence of its structural parameters,operational parameters and environmental parameters on the system performance.In this paper,the steady-state mathematical model of the system is established on the basis of experimental research,and the relationship between the system performance and the parameters is studied.Firstly,the performance of the prototype of small phase change cold storage system is tested,and the key parameters of the prototype during operation are recorded to verify the follow-up simulation results.The relationship between the flow area of the thermal expansion valve and the pressure difference of the diaphragm is obtained by designing the test experiment of the thermal expansion valve.Secondly,the component model of small phase change refrigeration system is established,including the lumped parameter model of thermal expansion valve and compressor,the distributed parameter model of parallel flow condenser and phase change refrigeration evaporator,and the component model is coupled by mass balance condition to form the system mathematical model.The system algorithm is used to converge the calculation of the whole system cycle.Thermal expansion valve model takes into account the influence of the superheat at the outlet of the evaporator on its opening,and its flow area is calculated by the relationship derived from the above-mentioned expansion valve experiment;the heat transfer coefficient outside the evaporator tube is calculated by the average heat transfer coefficient of the phase change material solidification process,and is calculated by the solidification and melting model in Fluent.Finally,the system performance is simulated and analyzed based on the established system model.The results show that with the increase of the inlet air temperature of the condenser,the refrigeration capacity of the system decreases,but the reduction of the refrigeration capacity is not obvious when the compressor speed is fixed,but the power of the compressor increases obviously,and the COP value of the system decreases accordingly;the increase of the head-on wind speed of the condenser will increase.The turbulence degree of air flow increases the heat transfer coefficient on the air side,and then increases the refrigeration capacity of the system,but there is an upper limit for the refrigeration capacity.With the increase of compressor speed,the refrigeration capacity and compressor power will increase significantly.The condenser of four processes has a higher heat transfer coefficient without producing too high pressure drop,so four-processes one has the highest refrigeration capacity and COP;the increase of the number of evaporator flat tube holes will increase the heat transfer area,but when it increases to 26 holes,the increase of refrigeration capacity will tend to be flat.