| With the pressure which was faced by the industry economic growth,energy decrease,environmental protection and social development,the electric vehicle is paid great attention by the people gradually.As a part of the electric vehicle's energy consumption,air conditioner system plays an important role and there are great value on the technological analysis of its heat-exchanger.The brazing process is a very important process in the production process of the heat exchanger.The brazing quality directly determines the heat transfer performance of the heat exchanger,so the research on the process is very meaningful.The main content of this paper is to study the cooling process after the parallel flow microchannel heat exchanger brazing process.In this paper,the related knowledge of electric vehicle and microchannel heat exchanger was briefly described,and the relevant knowledge and theory of microchannel heat exchanger studied in this paper are expounded.We have carried out the relevant test of its heat transfer performance,and obtained the change curves of the heat transfer and pressure drop with the flow rate.The results showed that the heat transfer and pressure drop of the microchannel heat exchanger increased with the increase of the flow rate,and the heat change was more obvious when the flow rate was smaller,and the pressure drop of the inlet and outlet of the heat exchanger was increased significantly when the flow rate was larger.So it was necessary to further study to find an optimal flow rate so that the heat transfer and pressure drop can be maintained at a reasonable value.In order to understand the cooling process after microchannel heat exchanger welding,this paper also used ANSYS finite element simulation to model and simulate the QDe2 electric vehicle air conditioning microchannel heat exchanger.The temperature distribution cloud image and the equivalent stress distribution of the microchannel heat exchanger were obtained,and the visualization analysis of the cooling process was realized.The simulation results showed the temperature and stress distribution of heat exchanger unit at different stages are different.Both in the drying furnace and brazing furnace,the temperature distribution of the heat exchange unit presents a law of "low central temperature,high temperature on both sides of the region".While in the cooling stage,since the heat transfer performance of the fin is superior to that of the flat pipe,the temperature distribution show a law of "high central temperature,low temperature on both sides of the region".The maximum temperature of the heat exchange unit in the drying furnace and the brazing furnace is about 180°C and 608°C,respectively.In addition,the stress distribution of the heat exchange unit in the drying furnace and the brazing furnace shows that the stress in the flat pipe area is larger and the stress in the fin and the weld area is smaller.During the cooling phase,the stress distribution on the surface of the heat exchange unit is more uneven.However,from the general trend,the equivalent stress in the central area is still larger and the equivalent stress on both sides is smaller.At the same time,there are two inflection points in the equivalent stress change of welding parts.The equivalent stress values at the two inflection points are about 60 MPa and 140 MPa,respectively.In addition,this paper simulated the temperature and stress distribution on the surface of heat exchange units at flow velocities of 2 m/s,5 m/s,8 m/s and 11 m/s,respectively.The simulation results showed that the temperature distribution of the heat transfer unit exhibits a similar parabolic law change under different flow rate conditions.During the beginning of the cooling period,the temperature dropped rapidly,and the temperature had a gradual decrease after 100 s.Finally,this article also briefly analyzed the welding temperature of the heat exchanger welding quality,and ultimately get the best heat transfer temperature of 590?. |
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