Optimization and Analyses on the Cooling-down Rate of an Auto-cascade Refrigeration System Operating With a Rectifying Column
Based on a quasi-steady-state simulation model,a method to optimize the cooling-down rate of an auto-cascade refrigeration system operating with a rectifying column and multi-component mixed refrigerant is proposed in the paper.Targeted on the maximum cooling capacity,the opti-mal suction pressure-evaporating temperature curve for a specified mixed refrigerant concentration can be obtained,which can be matched by the sectional suction pressure adjustment in the prac-tical applications to reduce the overall cooling-down time,and the concentration of mixed refrig-erant can be optimized to further improve the cooling-down rate based on this way.The fastest overall cooling-down time is achieved using the R50/R1150/R290/R600a as the mixed refrigerant(0.35/0.25/0.15/0.25 by mole)and corresponding shifting parameters(including two shifting temper-atures-20℃ and-105℃)and three shifting suction pressure 700 kPa,600 kPa and 550 kPa)for the sectional suction pressure adjustment,when the air temperature in the test chamber is dropped from 20℃ to-100℃.Calculation results also show that the optimal concentrations are different for different evaporating temperatures,and the cooling-down rate can be improved further if the concen-tration of the mixed refrigerant can be adjusted during the cooling-down process.The optimization methods used in this paper can also provide references for researches on cooling-down processes of other refrigeration systems using multi-component mixed refrigerants.
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