Heat Transfer MCQ Questions & Answers

81

A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because

A) Total heat transfer area of all the effects is -less than that in a single effect evaporator system B) Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect C) Boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system D) Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system

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Answer & Solution

Answer: Option B

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82

A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m³ and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m².K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is

A) 555 B) 55.5 C) 0.55 D) 0.15

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Answer & Solution

Answer: Option D

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83

A concentric double pipe heat exchanger as compared to the shell and tube heat exchanger for the same heat load requires

A) Less heating surface B) More space C) Lower maintenance cost D) None of these

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Answer & Solution

Answer: Option B

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84

Removal of __________ heat is involved in the condensation of a vapor under saturated conditions.

A) Super B) Sensible C) Latent D) Both B & C

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Answer & Solution

Answer: Option B

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85

A hot body will radiate heat most rapidly, if its surface is

A) White & rough B) Black & rough C) White & polished D) Black & polished

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Answer & Solution

Answer: Option B

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86

Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around __________ metres/second.

A) 1 B) 10 C) 20 D) 30

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Answer & Solution

Answer: Option A

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87

At what value of Prandtl number, the hydrodynamic and thermal boundary layers are identical?

A) 0.5 B) 1 C) 1.5 D) 80

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Answer & Solution

Answer: Option B

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88

Peclet number (Pe) is given by

A) Pe = Re.Pr B) $${\text{Pe}} = \frac{{{\text{Re}}}}{{{\text{Pr}}}}$$ C) $${\text{Pe}} = \frac{{{\text{Pr}}}}{{{\text{Re}}}}$$ D) Pe = Nu.Re

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Answer & Solution

Answer: Option A

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89

Pick out the correct equation.

A) $${\text{JH}} = \left( {{\text{St}}} \right){\left( {{\text{Pr}}} \right)^{\frac{2}{3}}} = \frac{{\text{f}}}{2}$$ B) $${\text{JH}} = \left( {{\text{St}}} \right){\left( {{\text{Pr}}} \right)^{\frac{1}{3}}} = \frac{{\text{f}}}{2}$$ C) $${\text{JH}} = {\left( {{\text{St}}} \right)^{\frac{2}{3}}}\left( {{\text{Pr}}} \right) = \frac{{\text{f}}}{2}$$ D) $${\text{JH}} = {\left( {{\text{St}}} \right)^{\frac{1}{3}}}\left( {{\text{Pr}}} \right) = \frac{{\text{f}}}{2}$$

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Answer & Solution

Answer: Option A

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90

Kirchoff s law applies to __________ radiation.

A) Total B) Monochromatic C) Both A & B D) Neither A nor B

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Answer & Solution

Answer: Option C

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Heat Transfer MCQ Questions & Answers | Chemical Engineering