单项选择题
Which of the lists forms of heat transfer, if any, is illustrated by the flow of combustion gases through a boiler?（）
A.Natural convection only
B.Forced convection only
C.Both natural convection and forced convection
D.None
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相关考题
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单项选择题
Auxiliary boilers can be classified as（）
A.water-tube natural circulation boilers
B.fire-tube boilers
C.water-tube forced circulation boilers
D.all of the above -
单项选择题
When the tilting box of a variable stroke axial-piston pump is perpendicular to the pump shaft, which of the following conditions will exist?（）
A.The pistons reciprocate
B.The ‘B’ end cylinder barrel rotates
C.There is no fluid flow
D.Power is transmitted hydraulically -
单项选择题
The hydraulic oil most likely to thin out when hot and thick when cold would have a viscosity index of（）
A.20
B.40
C.60
D.80
