Correlation Analysis Of Heat Exchange And Flow In Refrigerator Micro-channel Condenser And Tube-fin Evaporator

As the main component of the refrigeration system,the performance of the heat exchanger has a great impact on the performance of the entire refrigeration system.With the increasing attention of the country to energy saving and emission reduction and the fierce market competition environment,high performance and low cost are the development direction of the heat exchanger.Therefore,it is very important to test the performance of heat exchanger and the pressure drop of refrigerant flow.However,in the current heat transfer performance test research,one side is refrigerant,and the other side is common liquid heat medium such as water,few studies involve using air as the heat transfer medium outside the tube.And at present,the country has no relevant test standards for this.The relevant standards that are being developed still use water as a medium to test the performance of refrigerator heat exchangers.The test results seriously deviate from the actual application of heat exchangers,far behind the British standard in 1999(BS EN 1216:1999).Based on this,developed a heat exchanger performance test system which drived by a pump.Through this test system,the heat transfer performance and refrigerant flow pressure drop of evaporators or condensers with different experimental conditions and different structures can be tested.Then provide technical direction and data support for heat exchanger optimization.The experimental system includes a refrigerant supply system,a constant temperature wind tunnel,a control system,and a data acquisition system.The refrigerant supply system includes a test circuit and two temperature control circuits.Among them,the working refrigerant of the test circuit is R134 a,and the working refrigerant of the temperature control circuit is R404 A,and the experimental system is used to experimentally test the heat transfer and pressure drop characteristics of the fin and tube evaporator under different working conditions.The heat transfer capacity and the heat transfer coefficient of the test evaporator have been studied when the mass flow rate is 0.5 ? 3 g/s and the evaporation is 0.13 ? 0.26 MPa.The vapor quality of inlet is change from 0.2 to 0.5.The pressure drop during flowing also been studied.The results show that the heat transfer capacity,heat transfer coefficient and refrigerant flow pressure drop of the evaporator increase with the increase of refrigerant mass flow,and the heat transfer capacity,heat transfer coefficient decrease with the evaporation pressure and the vapor quality of inlet increase,but the refrigerant flow pressure drop increases with the increase of evaporation pressure and vapor quality of inlet.According to the experimental test results,taking the physical property parameters of the fluid on both sides of the evaporator and the characteristic size of the evaporator as the related parameters,the experimental correlation formula suitable for the overall heat transfer coefficient of the fin and tube evaporator which is obtained based on the Matlab nonlinear fitting.According to the previous experimental results of the micro-channel condenser with louvered fins tested by the research group,the heat transfer characteristics of the micro-channel condenser with louvered fins are theoretically analyzed,an experimental correlation suitable for calculating the heat transfer coefficient of the micro-channel condenser is obtained by Matlab nonlinear fitting.Comparing the calculation results by the correlation with the experimental values,80% of the data deviation is within ±10% and comparing the calculation results with the correlation calculation results of other researchers,the deviation is within the acceptable range.Through the analysis of the performance test data of the refrigerator micro-channel condenser and fin and tube evaporator,it is confirmed that the refrigerant is used as the medium of the performance test of the heat exchanger of the refrigerator to simulate the working state of the heat exchanger under the operating condition of the refrigerator,and to obtain the reliable experimental data,which can be realized technically.The fitting of the overall heat transfer coefficient can also avoid when use the experimental correlation to calculate the heat transfer coefficient,the internal and external convective heat transfer coefficients are calculated using appropriate correlations respectively,and then integrated to obtain the total heat transfer coefficient of the heat exchanger,which will introduce two fitting errors.This will be of great significance to the development of new heat exchangers and the design of refrigerator refrigeration systems.