Heat Transfer - Study Mode

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[#391] Heat sensitive materials can be concentrated in an evaporator employing

(A) Vacuum

(B) High pressure

(C) High residence time

(D) None of these

Correct Answer

(A) Vacuum

[#392] The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)

(A) α.T

(B) α.$$frac{1}{{ ext{T}}}$$

(C) α.T 4

(D) Independent of T

Correct Answer

(B) α.$$frac{1}{{ ext{T}}}$$

[#393] In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid.

(A) Equal to

(B) More than

(C) Less than

(D) Either more or less than (depending upon the fluid)

Correct Answer

(A) Equal to

[#394] A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are k A and k B and the specific heat capacities are C PA and C PB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when

(A) C PA > C PB

(B) C PA < C PB

(C) k A < 0.5 k B

(D) k A > 2 k B

Correct Answer

(C) k A < 0.5 k B

[#395] In which mode of heat transfer, the Biot number is important?

(A) Transient heat conduction

(B) Natural convection

(C) Forced convection

(D) Radiation

Correct Answer

(A) Transient heat conduction