Heat Transfer MCQ Questions & Answers

71

If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.

A) Increase B) Decrease C) Not affect D) Increase the condensing film co-efficient as well as

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Answer: Option B

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72

In forced circulation, the heating element is injected

A) Internally B) Externally C) Both A and B D) Neither A nor B

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Answer: Option A

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73

In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid

A) Varies directly as the area and the LMTD B) Directly proportional to LMTD and inversely proportional to the area C) Varies as square of the area D) None of these

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Answer: Option A

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74

The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16 m is 10 W/m². The temperature of the inside wall is -5°C. The outside wall temperature is

A) 25°C B) 30°C C) 35°C D) 40°C

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Answer: Option C

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75

The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as

A) $${\left( {\Delta {\text{T}}} \right)^{\frac{1}{4}}}$$ B) $${\left( {\Delta {\text{T}}} \right)^{\frac{1}{2}}}$$ C) $${\left( {\Delta {\text{T}}} \right)^{\frac{5}{4}}}$$ D) $${\left( {\Delta {\text{T}}} \right)^{\frac{3}{4}}}$$

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Answer: Option D

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76

The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m². The flux, when the element temperature is increased to 1000°C for the same furnace temperature is

A) 11.2 kW/m² B) 12.0 kW/m² C) 14.6 kW/m² D) 16.5 kW/m²

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Answer: Option D

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77

Pick out the wrong statement.

A) Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection B) The ratio N_Nu/N_Re . N_pr is called the Stanton number C) The Peclet number is a measure of the ratio of energy transport by convection to that by conduction D) The Colbum jH factor for heat transfer is given by N_st N_pr

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Answer: Option D

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78

Radiation energy is emitted by all the substances, which are above

A) 0°K B) 0°C C) 100°C D) Room temperature

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Answer: Option A

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79

The purpose of floating head in a heat exchanger is to

A) Avoid buckling of tubes B) Provide support for tubes C) Decrease the pressure drop D) Facilitate its lengthening, if needed

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Answer: Option A

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80

Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the

A) Less corrosion problems B) Flexibility possible in the baffle arrangement C) Low pressure drop D) High heat transfer co-efficient

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Answer: Option B

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Heat Transfer MCQ Questions & Answers | Chemical Engineering