单项选择题
A.the ability of oil to separate from water B.the temperature at which oil flows rapidly C.a measure of the water in a lube oil system D.an emulsion of different grades of oil
When subjected to high heat from a open flame, or an el...
单项选择题When subjected to high heat from a open flame, or an electric heating element, which of the listed refrigerants will break down and produce phosgene gas?（）
A.CO2 B.Methyl chloride C.R-22 D.Sulphur dioxide
Which of the following terms is used to identify the pr...
单项选择题Which of the following terms is used to identify the pressure of the liquid entering a pump?（）
A.Suction head B.Pump head C.Discharge head D.Total head
Ammonia when used as a refrigerant is valuable because ...
单项选择题Ammonia when used as a refrigerant is valuable because of its high efficiency, it is however （）.
A.toxic B.flammable C.explosive D.all of the above
