单项选择题
Excessive circulation of the lubricating oil with the refrigerant in a refrigeration system will cause （）.
A.carbon deposits on the compressor suction valves B.the evaporator temperature to increase C.rapid corrosion of the thermal expansion valve D.no operating problems
单项选择题 Scale accumulation on evaporator heat exchange surfaces （）.
单项选择题 In order to properly remove air from the casing of a centrifugal pump when starting, the pump should have a （）.
单项选择题 The valve best suited for throttling gas or liquid flow in a pipeline is the（）.
