在商业氟利昂制冷系统中,为了保护压缩机,防止压缩机停车期间制冷剂蒸气向压缩机曲轴箱迁移(migration,制冷剂蒸气这是向系统的最冷处迁移)并冷凝于润滑油中使油稀释,常采用系统自动抽空循环(pumpdown cycle),使系统的低压侧和压缩机曲轴在压缩机停车过程中和停车期间达到自动抽空的目的。 In commercial Freon refrigeration systems, in order to protect the compressor, refrigerant vapor is prevented from migrating to the compressor crankcase during the compressor stop (migration of refrigerant vapor which is the coldest part of the system) and condensation in the lubricating oil Dilution, often using automatic pump down cycle (pumpdown cycle), the system of low-pressure side and the compressor crankshaft in the compressor during parking and automatic pumping to achieve the purpose of parking.