Heat Transfer - Study Mode

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[#486] Thermal conductivity of a gas at low density, __________ with increase in temperature.

(A) Decreases

(B) Increases

(C) Remains unchanged

(D) May increase or decrease depends on the gas

Correct Answer

(B) Increases

[#487] In case of a supercooled solution, which is on the verge of crystallisation, the free energy of the solution as compared to that of the solid is

(A) More

(B) Less

(C) Same

(D) More or less depends on the nature of solution

Correct Answer

(A) More

[#488] In the equation Q = UAΔt
Δt is

(A) Geometric mean temperature difference

(B) Arithmetic mean temperature difference

(C) Logarithmic mean temperature difference

(D) The difference of average bulk temperatures of hot and cold fluids

Correct Answer

(C) Logarithmic mean temperature difference

[#489] A wall has two layers of materials A and B
each made of a different material. Both the layers have the same thickness. The thermal conductivity of materialA is twice that of B. Under the equilibrium, the temperature difference across the wall is 36°C. The temperature difference across the layer A is __________ °C.

(A) 6

(B) 12

(C) 18

(D) 24

Correct Answer

(B) 12

[#490] In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will

(A) Increase

(B) Decrease

(C) Remain unchanged

(D) Either increase or decrease depends on the coolant flow rate

Correct Answer

(C) Remain unchanged