Heat Transfer MCQ Questions & Answers

41

The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)_R and the co-efficient of performance as a heat pump (COP)_HP are

A) (COP)_R = (COP)_HP = 0.6 B) (COP)_R = 2.5; (COP)_HP = 1.5 C) (COP)_R = 1.5; (COP)_HP = 2.5 D) (COP)_R = (COP)_HP = 2.5

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Answer & Solution

Answer: Option C

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42

Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the

A) Maximum resistance in the series B) Sum of all resistances C) Average of all resistances D) Minimum resistance presents in the series

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Answer & Solution

Answer: Option B

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43

In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is

A) Infinity B) Zero C) Same as average heat transfer co-efficient for tube side D) None of these

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Answer & Solution

Answer: Option A

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44

Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place

A) Between two bodies in physical contact with each other B) Between two bodies not in physical contact with each other C) From one part of a body to the another part of the same body D) Both B & C

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Answer & Solution

Answer: Option B

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45

At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical?

A) 1 B) < 1 C) > 1 D) None of these

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Answer & Solution

Answer: Option A

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46

Pick out the wrong statement.

A) The controlling resistance in case of heating of air by condensing steam is in the air film B) The log mean temperature difference (LMTD) for counter flow and parallel flow can be theoretically same when any one of the fluids (hot or cold fluid) passes through the heat exchanger at constant temperature C) In case of a 1 - 2 shell and tube heat exchanger, the LMTD correction factor value increases sharply, when a temperature cross occurs D) Phase change in case of a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature

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Answer & Solution

Answer: Option C

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47

A body is called grey if the monochromatic emissivity of the body is

A) Zero B) Unity C) Same for all wavelengths D) Different for all wavelengths

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Answer & Solution

Answer: Option C

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48

Rate of crystallisation does not depend upon the

A) Extent of supersaturation B) Turbulence within the solution C) Number and active surface area of the crystals D) None of these

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Answer & Solution

Answer: Option D

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49

Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is __________ law.

A) Stefan's B) Dalton's C) Wien's D) Kirchoffs

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Answer & Solution

Answer: Option C

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50

Stefan-Boltzman law applies to __________ body.

A) Black B) White C) Grey D) Any colour

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Answer & Solution

Answer: Option A

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Heat Transfer MCQ Questions & Answers | Chemical Engineering