Heat Transfer

301. Prandtl number for most of dry gases is about

1. 0.001
2. 0.72
3. 70
4. 150

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302. Prandtl number is given by

1. C_P μ/a
2. hD/k
3. C_P μ/k
4. μ/h C_P

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303. Prandtl number is the ratio of

1. Momentum diffusivity to mass diffusivity
2. Momentum diffusivity to thermal diffusivity
3. Thermal diffusivity to mass diffusivity
4. Thermal diffusivity to momentum diffusivity

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304. Prandtl number is the reciprocal of

1. Thermal diffusivity/Momentum diffusivity
2. Thermal diffusivity × Momentum
3. Thermal diffusivity × Mass diffusivity
4. Mass diffusivity × Momentum diffusivity

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305. Presence of a non-condensing gas in a condensing vapour

1. Increases the rate of condensation
2. Decreases thermal resistance
3. Is desirable to increase the film co-efficient
4. None of these

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306. Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.)

1. √d
2. d
3. d²
4. d^1.5

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

1. 0°K
2. 0°C
3. 100°C
4. Room temperature

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308. Radiation heat losses from satisfactorily insulated high pressure boiler may be about _________ percent.

1. 1
2. 7
3. 18
4. 26

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309. Radiation heat transfer rates does not depend upon the

1. Type of absorbing surface
2. Distance between the heat source and the object receiving the heat
3. Surface area and temperature of the heat source
4. None of these

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310. Radiator of an automobile engine is a _________ type of heat exchanger.

1. Co-current
2. Cross-current
3. Counter-current
4. Direct contact

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