Heat Transfer

81. Circulation pump is located below the evaporator to

1. Avoid cavitation
2. Avoid frequent priming
3. Create more suction head
4. None of these

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82. Colburn analogy is applicable for the value of Prandtl number from

1. 0.001 to 1
2. 0.6 to 120
3. 0.5 to 5
4. 120 to 400

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83. Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m².°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the

1. Higher condensing film co-efficient is desired
2. Condensate is corrosive in nature
3. Lower pressure drop through the exchanger is desired
4. Temperature of the incoming vapor is very high

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84. Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)

1. x/KA
2. KA/x
3. K/Ax
4. A/Kx

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85. Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is

1. 0.1
2. > 1
3. < 1
4. 1

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86. Controlling heat transfer film co-efficient is the one, which offers _________ resistance to heat transfer.

1. No
2. The least
3. The largest
4. Lower

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87. Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the _________ zone.

1. Laminar
2. Transition
3. Both 'a' & 'b'
4. Highly turbulent

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88. Convective heat transfer, in which heat is transferred by movement of warmed matter is described by

1. Fourier's law
2. Newton's law of cooling
3. Fick's law
4. None of these

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89. Correction is applied to LMTD for _________ flow.

1. Parallel
2. Counter
3. Cross
4. None of these

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90. Corrosiveness of steam condensate is due to the presence of

1. CO₂
2. Dissolved O2
3. Both (A) & (B)
4. Neither (A) nor (B)

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