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Theoretical and Experimental Research on R/Fs Based on Cooling Transformer

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Tutor: TangLiMing
School: Zhejiang University
Course: Refrigeration and Cryogenic Engineering
Keywords: dual-loop,cooling transformer,energy saving,refrigerator/freezer
CLC: TM925.21
Type: Master's thesis
Year:  2014
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Abstract:
After six decades of development, the production and sales of refrigerator/freezers (RFs) in China have reached10million, the energy consumption of RFs have become considerable because of its high possession rate. Research on energy saving of RFs also became more and more important and the state and industries have focused on it.Cooling transformer can transform low-grade cooling capacity into high-grade cooling capacity in multi-temperature-level refrigeration system; aim to achieve better utilization of energy. After analyzing the characteristic of different refrigeration cycles, a new dual-loop refrigeration cycle based on cooling transformer was put forward by adding a heat exchanger into conventional two-compressor dual-loop RFs (CIDRFs). The heat exchanger can sub-cool the refrigerant of freezer-cycle (F-cycle) and transform part of refrigerator-cycle (R-cycle) low-grade cooling capacity into F-cycle high-grade cooling capacity, which can improve the RF¡¯s equivalent coefficient of performance (EC).As the following, the major contents and key points are:(1) The influence of the key parameters on the performance of the system is obtained by the thermodynamics analysis, with EES software. Besides, theoretical model is made and the EC of the new system is compared with the EC of CDTRFs and evaporator in series cycle RFs (ESRFs).(2) An experimental setup was designed and fabricated for further research. The setup can work in different models, which can compare the working parameters of conventional two-compressor dual-loop RFs with the new system. (3) Experimental results show that:the cooling-transform contribution rate (TR) is0.257when the storage temperature storage temperature is-5¡æ, the freezing temperature is-25¡æand the condensation temperature is44¡æ, while the condensation temperature is30¡æ, the TR is0.148, which indicate that with the condensation temperature improving, the TR of RFs based on cooling transformer will increase.(4) Experimental results show that:the EC of RFs based on cooling transformer is equal to the EC of CTDRFs when the condensation temperature is the same, while the load ratio of F-cycle and R-cycle (RTFR) of RFs based on cooling transformer is much higher than the RTFR of CTDRFs. From the cold grade point of view, the results verify the performance of RFs based on cooling transformer is better than CTDRFs. When the storage temperature storage temperature is-5¡æ, the freezing temperature is-25¡æ, the condensation temperature is44¡æand the load ratio of F-cycle and R-cycle is0.917, the EC of the new system can improve about8.48%, compared with the CTDRFs.
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