Numerical Simulation And Experimental Investigation On Parallel Flow Microchannel Heat Exchanger

Parallel flow microchannel heat exchangers are widely used in automotive and household air conditioners due to their advantages of high heat exchange efficiency,small size,and light weight.However,when the parallel flow microchannel heat exchanger is used as the evaporator,because the refrigerant at the inlet of the evaporator is in a vapor-liquid two-phase state,there is a speed slip,which causes uneven distribution of vapor and liquid refrigerant in the evaporator,which decreased heat transfer efficiency.This paper uses a combination of numerical simulation and experimental investigation to explore the heat transfer and pressure drop characteristics of the microchannel parallel flow evaporator,as well as the refrigerant distribution characteristics.And put forward a new idea to improve the refrigerant distribution characteristics by changing the protruding depth of the flat tube in the header.The main research contents of this paper are as follows:1.Using the comprehensive performance test bench for automobile air conditioners,the air enthalpy method is used to conduct experimental investigations on a six-process two-row parallel flow microchannel evaporator,which provides verification data for the subsequent simulation exploration.2.Using MATLAB R2019 b software,the heat transfer and pressure drop characteristics in the above-mentioned six-process two-row parallel flow microchannel evaporator were simulated.The comparison with the experimental results verified the reliability of the simulation model.Using this model,the structural parameters of flat tubes and louver fins were optimized.3.For the multi-element parallel flow microchannel evaporator,the uneven distribution of refrigerant in the first process is serious.Use ANSYS 2020R2 Fluent simulation software to simulate the refrigerant distribution characteristics in the first process of the parallel flow microchannel evaporator.Compared with the previous experimental data,the reliability of the model is proved.The model is used to optimize the refrigerant inlet conditions,the diameter of the header and the protrusion depth of the flat tube.4.A new idea is proposed to improve the distribution characteristics of refrigerant by changing the protruding depth of different flat tubes in the header,and by combining the heat transfer and pressure drop model and the distribution characteristic model,it was found that the heat transfer was improved.The new parallel flow microchannel evaporator structure with variable flat tube protruding depth proposed in this paper can effectively improve the problem of uneven refrigerant distribution.This article provides a theoretical basis for subsequent promotion research.