单项选择题
A.radiation B.conduction C.convection D.condo-radiation
A gate valve installed in a pipeline should be （）.A.use...
单项选择题A gate valve installed in a pipeline should be （）.
A.used in either the fully dosed or fully opened position B.installed with the stem down C.used for steam service only D.used to throttle or regulate the flow of liquid
Which of the following modes of heat transfer does NOT ...
单项选择题Which of the following modes of heat transfer does NOT require any physical contact between a warmer and a cooler substance?（）
A.Radiation B.Conduction C.Natural convection D.All of the above
Which of the valves listed should be used either in the...
单项选择题Which of the valves listed should be used either in the fully opened or the fully closed position?（）
A.A gate valve B.A globe valve C.Any check valve D.Any needle valve
