单项选择题
A.High pressure compressors are more efficient than low pressure compressors
B.Mechanical efficiency divided by compressor efficiency will equal the overall efficiency of the compressor unit
C.Two stage compressors are generally more efficient than single stage compressors
D.The volumetric efficiency is decreased in multistage compressors
单项选择题 The ability of an oil to separate cleanly from an oil and water mixture is referred to as its （）.
单项选择题 When the relief valve opens it discharges high pressure refrigerant vapor to the （）.
单项选择题 If the discharge valve is closed before the drive motor is stopped, which of the following types of pumps will most likely be damaged?（）