卧式冷柜启停过程中制冷剂迁移的动态特性

针对制冷系统启停过程存在制冷剂的迁移和再分配问题,以单温卧式冷柜BC/BD-379HBN为载体,研究系统内制冷剂迁移的动态特性及其对系统性能的影响.以蒸发器内制冷剂沿程变化,启动阶段依次分为蒸发器制冷剂迁出、蒸发器两相区增长、蒸发器两相区稳定3个阶段.结果表明:阶段1,压缩机流量大于毛细管供液量,高压压力迅速升高;阶段2,随毛细管供液量增大,冷凝器出口温度趋于稳定,系统高低压差重建完成;阶段3,蒸发器两相段到达出口,制冷量达到最大.启动阶段的制冷剂再分配用时3.5 min,占开机时长的32%,而期间制冷量很小,存在较大的迁移损失.

Dynamic characteristics of the refrigerant migration during the on-off processes of a horizontal freezer

Refrigerant migration and redistribution will occur during the on-off processes of a refrigerating system. Based on a horizontal freezer BC/BD-379HBN, dynamic characteristics of the refrigerant migration and its effects on the freezer performance were studied experimentally. Results show that the process of the start-up can be divided into three stages, i.e., refrigerant emigrating from evaporator, evaporator two-phase section increasing stage, and evaporator two-phase section stabilized stage. In the first stage, the refrigerant flowrate through the compressor was larger than that through the capillary tube, resulting in an increase in the condensing pressure. In the second stage, condenser outlet temperature stabilized gradually with the increase in the refrigerant flowrate through the capillary tube, indicating the end of the pressure-difference rebuilt process. In the third stage, a maximum cooling capacity was obtained due to the fact that the two-phase section covered the whole evaporator tube pass. The refrigerant redistribution process occupied 3.50 minutes which was about 32% of a single compressor-on period. However, the cooling capacity during this process was small. In conclusion, a large migrating loss was introduced by the start-up refrigerant migration process of the freezer.