辅助循环回热器对直接接触冷凝制冷循环的影响

Effects of adding vapor-liquid heat exchanger in auxiliary supercooled cycle on performance of direct contact condensing refrigeration cycle

对R717/R744-HDCC、R404A/R744-HDCC、R449A/R744-HDCC三种辅助过冷循环带回热器的直接接触冷凝制冷循环进行热力学分析,探究辅助过冷循环回热器对直接接触冷凝制冷循环热力性能的影响。得出:辅助过冷循环加回热器对R404A/R744-HDCC、R449A/R744-HDCC两种循环有利,可使性能系数增加,冷凝器散热量减小。制冷循环性能系数最高可分别增加6.47%、1.46%,而冷凝器散热量最高可减少2%、0.46%。而辅助过冷循环加回热器对R717/R744-HDCC制冷循环不利,会使制冷循环性能系数减小,冷凝器散热量增加.性能系数最多减少5.9%,冷凝器散热量最多增加1.9%。在相同的运行工况和供冷条件下,在辅助过冷循环中采用回热器会减少R717/R744-HDCC、R404A/R744-HDCC、R449A/R744-HDCC三种直接接触冷凝制冷循环中R717、R404A、R449A的质量流量,分别减少了9.75%、29.8%、20.7%。增设回热器还会导致压缩机排气温度的升高。

Thermodynamic analysis on direct contact condensing refrigeration cycles of R717/R744-HDCC,R404 A/R744-HDCC,R449 A/R744-HDCC with vapor-liquid heat exchanger in auxiliary supercooled cycle was carried out to investigate the effect of adding vapor-liquid heat exchanger in auxiliary supercooled cycle on thermal performance of direct contact refrigeration cycle. The following conclusions are obtained. Adding vapor-liquid heat exchanger in auxiliary subcooled cycle is beneficial to the cycle of R404 A/R744-HDCC and R449 A/R744-HDCC,which can increase the coefficient of performance and reduce the condenser heat load. The performance coefficient of refrigeration cycle can increase by 6.47% and 1.46%,while the condenser heat load of refrigeration cycle can reduce by 2% and 0.46%,respectively. But adding vapor-liquid heat exchanger in auxiliary subcooled cycle is harmful to the cycle of R717/R744-HDCC,which can reduce the coefficient of performance and increase the condenser heat load. The performance coefficient of refrigeration cycle can be reduced by 5.9% at most,and the condenser heat load of refrigeration cycle can be increased by 1.9% at most. Under the same operating conditions,adding vapor-liquid heat exchanger in auxiliary supercooled cycle in direct contact condensing refrigeration cycles of R717/R744-HDCC,R404 A/R744-HDCC and R449 A/R744-HDCC,the mass flow rate of R717、R404 A and R449 A will be reduced by 9.75%、29.8% and 20.7%, respectively.Besides, adding vapor-liquid heat exchanger in auxiliary supercooled cycle will increase the discharging temperature of compressor.