Engineering :: Heat Transfer

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81.

The average heat transfer coefficient for dropwise condensation is

A.	more than that for filmwise condensation	B.	less than that for filmwise condensation
C.	nearly same as that for filmwise condensation	D.	always less than 40 Btu/(hr. ft2 ?F)

82.

The heat flux in the free convection regime of pool boiling varies as the

A.	?T3	B.	?T5/4
C.	?T2	D.	?T1/4

83.

The peak heat flux in a boiling curve is called

A.	the burnout point	B.	the Leidenfrost point
C.	the boiling point	D.	the Nusselt point

84.

The surface tension of water

A.	is independent of temperature	B.	decreases with increasing temperature
C.	increases with increasing temperature	D.	decreases linearly with increasing temperature

85.

At atmospheric pressure the critical temperature drop for water is usually between

A.	70 and 90?F	B.	70 and 90?C
C.	40 and 50?F	D.	180 and 212?F

86.

The transfer of heat energy from a heated body to a colder body by the emission of heat waves is called

A.	conduction	B.	natural convection
C.	forced convection	D.	radiation

87.

Heat waves

A.	travel only in straight lines	B.	travel only in circular lines
C.	involve some kind of matter to carry the heat energy	D.	travel in haphazard manner

88.

Heat transfer by radiation is described by

A.	Newtons law of cooling	B.	Ficks law
C.	Fouriers law	D.	Stefan-Baltzmann law

89.

According to Stefan-Baltzmann law the radiant heat transfer is proportional to

A.	the absolute temperature	B.	the second power of the absolute temperature
C.	third power of the absolute temperature	D.	the fourth power of the absolute temperature

90.

The Stefan-Baltzmann constant (?) is independent of

A.	surface	B.	medium
C.	temperature difference and thickness only	D.	all of the above