Engineering :: Heat Transfer

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31.

If the pipe radius (r) is less than the critical radius (rc) the heat loss from pipe

A.	remains unaffected with addition of insulation	B.	decreases with addition of insulation until r = rc and then increases with further addition of insulation
C.	increases with addition of insulation until r = rc and then decreases with further addition of insulation	D.	decreases for any addition of insulation

32.

If the pipe radius (r) is greater than the critical radius (rc) the heat loss from pipe

A.	remains constant for any addition of insulation	B.	increases for any addition of insulation
C.	decreases for any addition of insulation	D.	increases with addition of insulation until r = rc and then decreases with further addition of insulation

33.

The critical radius for curved insulation

A.	remains unaffected with change in the thermal conductivity of insulation	B.	decreases with decrease in the thermal conductivity of insulation
C.	increases with decrease in the thermal conductivity of insulation	D.	increases linearly with decrease in the thermal conductivity of insulation

34.

An industrial furnace will is constructed of 0.6 ft thick fireclay brick having k = 0.6 Btu/(hr. ft?F). This is covered on the outer surface with a 0.12 ft thick layer of insulating material having k=0.04 Btu/(hr.ft?F). The innermost surface is at 100 ?F). The steady state heat transfer per square foot is

A.	450 Btu/(hr. ft2)	B.	533.33 Btu/(hr. ft2)
C.	400 Btu/(hr. ft2)	D.	800 Btu/(hr. ft2)

35.

If heat is generated inside a plane wall the steady state temperature distribution in a very large thin plane wall having a constant thermal conductivity and steady uniform face temperatures follows

A.	linear law	B.	logarithmic law
C.	parabolic law	D.	hyperbolic law

36.

For a steady state current of I passing through a electrical conductor having a resistance of R the heat generated is given by

A.	IR2	B.	IR
C.	I2R	D.	I2R2

37.

The Fourier number (NFO) is defined as

A.	tL2/?	B.	?t/L2
C.	hL/k	D.	hk/L

38.

The Fourier number is used in the analysis of problems involving

A.	steady state heat conduction	B.	transient heat conduction
C.	heat transfer by natural convection	D.	heat transfer by radiation

39.

The Biot number is defined as

A.	?t/L2	B.	?t2/L2
C.	hk/L	D.	hL/k

40.

The Biot number is important in the problems involving

A.	heat transfer by radiation	B.	heat transfer by natural convection
C.	heat transfer by forced convection	D.	transient heat conduction