单项选择题
Air or noncondensable gas is removed from a refrigeration system by a （）
A.separating chamber B.system of baffles C.purge valve D.vacuum reducing valve
单项选择题 Where are the zinc plates located?（）
单项选择题 The device used for low-pressure control and high-pressure cutout on a compressor is called a（）
单项选择题 The purpose of the purge valve at the top of the condenser in a refrigerating system is to（）
