Performance Study Of Dual-loop Coupled Refrigeration System Used In Refrigerator/Freezer

With the rapid development of national economy and the continuous improvement of life quality, refrigerator/freezers become more popular. Meanwhile, large capacity R/Fs with multi-temperatures chambers are also getting more proportion. Refrigerator/Freezer is a big branch in home electrical appliances. Popularization of R/Fs increases the energy consumption of it. Therefore the energy saving about Refrigerator/Freezer has become the important component of national energy conservation policy.Applying the evaporation-subcooler in the refrigeration systems of large capacity R/Fs is a new direction of energy saving, In this thesis, based on the theoretical study and laboratory confirmatory test, a new R/F prototype with dual-loop coupled refrigeration system was designed and its actual performance was investigated. Major contents and key points are:(1) According to the structure of conventional refrigerator prototype and the experimental process, a new structure of dual-loop coupled refrigeration system and corresponding components were designed and a prototype of the new system was built up.(2) Experimental study was carried out on the prototype of the new system. The variations of evaporating temperature, condensing temperature, suction pressure and exhaust pressure during both independent operation mode and coupling operation mode were analyzed, same as the power consumption and chamber temperature variation under different operation modes. Based on the experimental results, component structures and operation scheme of the new refrigeration system was optimized.(3) A dynamic model was established to simulate the performance of dual-loop coupled refrigeration system. It was verified by experimental results. Then the dynamic model was used to analyze and compare the performance of the new refrigeration system under both independent operation mode and coupling operation mode. Assuming that efficiencies of compressor in both refrigerator cycle and freezer cycle are equal, dual-loop coupling operation mode can relatively save 11.5% power consumption when compared with independent operation mode per 24h, indicating that the coupling operation mode has large energy saving potential.(4) According to the scheme of optimization, the new prototype system was further improved and tested. The operational performance of coupling operation mode (dual-loop coupled refrigeration system) and independent operation mode (independent dual-loop refrigeration system) was compared. Results indicated that both the running time and total energy consumption of freezer cycle under coupling operation mode were reduced, leading to the improvement of the efficiency of freezer cycle, while those of the refrigerator cycle were increased, leading to the decrease of the efficiency of refrigerator cycle. Because of the cooling capacity of refrigerator cycle was relatively small, the efficiency of compressor of refrigerator cycle is lower than that of freezer cycle. Therefore, the difference of total power consumption between two operation modes is small.