Heat Transfer

21. Film coefficient is defined as Inside diameter of tube

1. Equivalent thickness of film
2. Thermal conductivity Equivalent thickness of film Specific heat x Viscocity
3. Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
4. Film coefficient x Inside diameter Thermalconductivity
5. none of the above.

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22. he amount of radiation mainly depends on

1. nature of body
2. temperature of body
3. type of surface of body
4. all of the above
5. none of the above.

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23. he concept of overall coefficient of heat transfer is used in case of heat transfer by

1. conduction
2. convection
3. radiation
4. conduction and convection
5. convection and radiation.

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24. he emissive power of a body depends upon its

1. temperature
2. wave length
3. physical nature
4. all of the above
5. none of the above.

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25. he energy distribution of an ideal reflector at higher temperatures is largely in the range of

1. shorter wavelength
2. longer wavelength
3. remains same at all wavelengths
4. wavelength has nothing to do with it
5. none of the above.

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26. he ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as

1. Krichoff's law
2. Stefan's law
3. Wien' law
4. Planck's law
5. Black body law.

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27. he ratio of the energy absorbed by the body to total energy falling on it is called

1. absorptive power
2. emissive power
3. absorptivity
4. emissivity
5. none of the above.

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28. he thermal diffusivities for gases are generally

1. more than those for liquids
2. less than those for liquids
3. more than those for solids
4. dependent on the viscosity
5. same as for the liquids.

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29. he thermal diffusivities for solids are generally

1. less than those for gases
2. jess than those for liquids
3. more than those for liquids and gases
4. more or less same as for liquids and gases
5. zerci.

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30. he total emissivity power is .defined as the total amount of radiation emitted by a black body per unit

1. temperature
2. thickness
3. area
4. time
5. area and time.

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