单项选择题
A.physical state B.temperature C.atmospheric pressure D.sensible pressure
（） will be used to blow away the combustion products fr...
单项选择题（） will be used to blow away the combustion products from the tube surfaces.
A.The blow down valve B.The scum valve C.The air release cock D.The soot-blower
In motor ship, （） is often used to recover some of the ...
单项选择题In motor ship, （） is often used to recover some of the heat carried in the exhaust gases from the main engine.
A.an diesel oil heater B.a waste heat boiler C.a fresh water generator D.all the above
Impurities from the boiler water surface can be removed...
单项选择题Impurities from the boiler water surface can be removed through the （）.
A.safety valve B.blow down valve C.scum valve D.feed check valve
