Heat Transfer - Study Mode

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[#281] The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m 2 . The approximate surface temperature (K) is (Stefan-Boltzman constant = 5.67 × 10 -8 W/m 2 .K 4 )

(A) 1000

(B) 727

(C) 800

(D) 1200

Correct Answer

(A) 1000

[#282] Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 kcal/hr.m 2 .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the

(A) Higher condensing film co-efficient is desired

(B) Condensate is corrosive in nature

(C) Lower pressure drop through the exchanger is desired

(D) Temperature of the incoming vapor is very high

Correct Answer

(B) Condensate is corrosive in nature

[#283] If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will

(A) Increase by 1.8 times

(B) Decrease by 22

(C) Increase by 216

(D) Remain unchanged

Correct Answer

(C) Increase by 216

[#284] The thermal radiation emitted by a body is proportional to T n , where T is its absolute temperature. The value of 'n' is exactly 4 for

(A) Black painted bodies only

(B) All bodies

(C) Polished bodies only

(D) A black body

Correct Answer

(B) All bodies

[#285] Convective heat transfer, in which heat is transferred by movement of warmed matter is described by

(A) Fourier's law

(B) Newton's law of cooling

(C) Fick's law

(D) None of these

Correct Answer

(B) Newton's law of cooling