Performance Test And Analysis Of Microchannel Condensers For Refrigerators

Refrigerator heat exchanger performance is particularly important for energy saving of the refrigerator system.In this paper,we designed a system which can test the performance of different specifications of the refrigerator heat exchanger system,with a set of gear pump as a driving force.Then we tested the performance of air-cooled evaporator and condenser using R134 a as refrigerant.The refrigerator heat exchanger performance testing system had been developed.Compressor was used as power in compressor system,it had lots of unique features,for example,the import and export of compressor were superheated,and it had large pressure difference.Unlike compressor system,when the gear pump was used as the driving force of the test system,the pressure difference between the inlet and outlet of gear pump was small and the refrigerant at the inlet and outlet of gear pump must be liquid.The bubbles in refrigerant liquid will cause cavitation of the gear pump and damage pump head seriously,which will lead to unstable refrigerant mass flow further.The mass flow of refrigerator heat exchanger was small,we must ensure the flow was stable in testing.Through the development of the system and thermodynamic analysis of the refrigerant,the test system can be operated stably.And when we tested the samples of the evaporator and the condenser,the fluctuation range of the flow rate did not exceed 10%.The consistency of repeated experiments under the same experimental conditions was good.The evaporator and condenser heat transfer capacity,heat transfer coefficient and pressure drop were tested and compared with other literature data to verify the accuracy of the experimental system and the reliability of the test data.For verifing the accuracy of the experimental test results theoretically,we tested the refrigerator condenser sample.The results showed that,with the condensation pressure decreased,the heat transfer capacity of the condenser also decreased,but the heat transfer coefficient and the pressure drop between the inlet and outlet of the condenser were increased,which was related to the thermal properties of the refrigerant.When the ambient temperature was low,the temperature difference between the condensing temperature and the ambient temperature was large,the heat exchange driving force will be more powerful,which promoted the heat exchange,resulting in the heat exchange effect and heat transfer capacity increased;when the flow of refrigerant was different,the difference of the heat transfer capacity was relatively small,and compared with the down and up flow mode,heat transfer coefficient of the refrigerant was higher in up and downflow mode.Under the same condensation pressure,the degree of subcooling of the refrigerant at the outlet of the condenser decreased after the refrigerant flow rate increased.By comparing the result of the correlation calculation with experimental data,the deviation of the heat transfer coefficient was between-10% and + 20%,which further verified the results of the test system were precise.Through developing and improving the refrigerator heat exchanger performance testing system,the performance of heat exchanger can be accurately tested.Analysising the factors that affect the heat transfer and resistance will play a guide role in the heat exchanger development process,and it has great significance at energy saving and environmental protection.