Refrigerant Flow And Heat Transfer Characteristics In Microchannel Evaporator

Microchannel heat exchangers(MCHX)has the advantages of compact structure,high heat transfer efficiency,low weight and low cost.At present,microchannel heat exchanger has been widely used in automobile air conditioning system and gradually replacing the traditional heat exchanger in the fields of household air conditioning,commercial air conditioning,heat pump water heater,refrigerator and cold chain.But there are still some problems existing when MCHX is used as the evaporators in the automotive air conditioning system,such as refrigerant maldistribution among parallel microchannel tubes,condensed water discharge,and easy to frost.These problems restrict the application of microchannel heat exchanger in a wider range.In this paper,the flow and heat transfer characteristics of refrigerant in microchannel evaporator are studied through numerical simulation and experiment.To solve the technical difficulties in the application of microchannel heat exchanger as evaporator,promote the application of microchannel heat exchanger in the industry,and facilitate the energy conservation,environmental protection and sustainable development.Research contents mainly include:1.Based on the existing research foundation,the mathematical model of evaporator heat transfer and pressure drop was established by using the distributed parameter method.The effect of tube parameters and fin parameters on the evaporator was analyzed in order to provide theoretical basis for the optimization of evaporator parameters.2.CFD numerical simulation was conducted to simulate the flow of refrigerant in different structure headers.The influence of different structure designs on the refrigerant distribution and heat transfer performance in the headers was studied through experiments,providing guidance for the header design.3.Combined with the experimental results,the effects of refrigerant maldistribution on the evaporator's heat transfer performance,air outlet temperature uniformity and frost formation were analyzed.At the same time,a simulation software for microchannel evaporator considering the uneven distribution of refrigerant is developed,which is convenient for the rapid prediction of the performance change of heat exchanger under different distribution of refrigerant and provides support for heat exchanger design.