Heat Transfer

471. Which of the following is correct?

1. Rate = Driving force × Resistance
2. Driving force = Rate × Resistance
3. Resistance = Driving force × Rate
4. Rate = Resistance/Driving force

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472. Which of the following is directly concerned with the heat transfer?

1. Strouhal number
2. Sherwood number
3. Euler number
4. Grashoff number

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473. Which of the following is generally considered as opaque surface towards radiations?

1. Gases
2. Solids
3. Liquids
4. Both (B) and (C)

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474. Which of the following is not concerned with the heat transfer?

1. Brinkman number
2. Stanton number
3. Schmidt number
4. Peclet number

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475. Which of the following is not used as a medium for high temperature heating ?

1. Dowtherm
2. Mercury
3. Liquid metal (e.g. molten sodium)
4. Fused salts (e.g., an eutectic mixture of 53% KNO₃, 40% NaNO₂and 7% NaNO₃)

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476. Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface?

1. Liquid density
2. Liquid viscosity
3. Hot surface temperature
4. Interfacial tension

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477. Which of the following is the most widely used heat insulating material for pipelines carrying steam?

1. Tar dolomite bricks followed by asbestos
2. Fireclay refractory followed by aluminium sheet
3. Cotton followed by aluminium foil
4. 85% magnesia cement and glass wool

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478. Which of the following is unimportant in forced convection?

1. Reynolds number
2. Prandtl number
3. Grashoff number
4. None of these

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479. Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger?

1. Tube side pressure drop and the heat transfer rate
2. Convective heat transfer co-efficient
3. Effective tube surface area for convective heat transfer
4. All (A) (B) and (C)

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480. Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger?

1. Corrosiveness & fouling characteristics
2. Pressure
3. Viscosity
4. Density

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