Heat Transfer

111. 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

1. Less corrosion problems
2. Flexibility possible in the baffle arrangement
3. Low pressure drop
4. High heat transfer co-efficient

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112. Film boiling is usually not desired in commercial equipments, because

1. The heat transfer rate is low in view of the large temperature drop
2. It is difficult to maintain
3. It is not economic
4. None of these

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113. Film boiling occurs at _________ pressure.

1. Atmospheric
2. Sub-atmospheric
3. Negative
4. Very high

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114. Film condensation is promoted on a/an _________ surface.

1. Oily
2. Coated
3. Clean & smooth
4. Dirty

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115. Finned tube heat exchangers

1. Give larger area per tube
2. Use metal fins of low thermal conductivity
3. Facilitate very large temperature drop through tube wall
4. Are used for smaller heat load

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116. Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the

1. Existence of thermal boundary layer
2. Temperature gradient produced due to density difference
3. Buoyancy of the bubbles produced at active nucleation site
4. None of these

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117. For _________ Prandtl number values, the heat conduction will be negligible in the buffer zone.

1. Extremely low
2. Low
3. High
4. No

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118. For a cold dilute feed to produce thick viscous liquor, backward feeding as compared to forward feeding results in

1. Increased economy
2. Decreased economy
3. Lower capacity
4. No effect on economy

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119. For a counter current heat exchanger with Ti h = 80°C, T°c = 60°C, T°h = 50°C and Ti c = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy

1. d²T/dZ² > 0
2. d²T/dZ² = 0
3. d²T/dZ² < 0
4. dT/dZ = 0

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120. For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are

1. Same
2. Different
3. Never different
4. Linearly related

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