Abstract:

The performances of R717/R744-DCC refrigeration cycle, the R744 gas discharged from R744 compressor contacts directly with the R744 super-cooled liquid provided auxiliary super cooling by R717 refrigeration cycle, are analyzed. The following conclusions are obtained. The optimum condensing temperatures of R744 main cycle exist in the R717/R744-DCC refrigeration cycle, and at the optimum condensation temperatures, the maximum coefficient of performance and minimum R717 condenser heat load are obtained. With the increasing of super cooling degree of R744 main cycle supercooled liquid, the maximum coefficient of performance reduces, the minimum R717 condenser heat load increases, the condensation temperatures of R744 main cycle increases, and the refrigerant mass flow rate of R744 evaporator decreases. Meanwhile, compared with that of R717/R744 cascade refrigeration cycle, at the same operating conditions and the optimum R744 main cycle condensing temperatures, the maximum coefficient of performance of R717/R744-DCC cycle increases 5.2%, and the minimum R717 condenser heat load reduces 1.6%. Furthermore, in the range of -10-8℃ condensation temperatures of R744 main cycle, the mass flow rate of R744 evaporator of R717/R744-DCC refrigeration cycle reduces 1.75%-2.61%,and the mass flow rate of R717 condenser of R717/R744-DCC refrigeration cycle reduces about 0.51%-0.82%.

Key words: R744 gas, R744 super-cooled liquid, direct contact condensation, R717 assisted supercooling, refrigeration cycle, thermal performance

摘要：

对R717循环辅助过冷、R744主循环制冷压缩机排出的气体与R744过冷液直接接触冷凝的R717/R744-DCC制冷循环的热力性能进行分析，得出：R717/R744-DCC直接接触冷凝制冷循环存在最佳的R744主循环冷凝温度，并获得最优的性能系数和最低的R717冷凝器散热量。R744主循环过冷液体的过冷度增大，最优的性能系数降低，最低R717冷凝器散热量增大，对应的R744主循环冷凝温度升高，R744蒸发器的质量流量减少。与常规R717/R744复叠式制冷循环的热力性能比较，在相同的运行工况和最佳R744主循环冷凝温度下，R717/R744-DCC直接接触冷凝制冷循环最优性能系数提高了5.2%，最低R717冷凝器散热量减少了1.6%。R744主循环冷凝温度在-10～8℃范围内，R717/R744-DCC直接接触冷凝制冷循环R744蒸发器的制冷剂质量流量减少了1.75%～2.61%，R717冷凝器的制冷剂流量减少了0.51%～0.82%。

关键词: R744气体, R744过冷液体, 直接接触冷凝, R717辅助过冷, 制冷循环, 热力性能