Chemical Engineering - Heat Transfer

1. 

Which area is used in case of heat flow by conduction through a cylinder ?

A. Logarithmic mean area
B. Arithmetic mean area
C. Geometric mean area
D. None of these

Answer: Option A

Explanation:

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2. 

Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place

A. between two bodies in physical contact with each other.
B. between two bodies not in physical contact with each other.
C. from one part of a body to the another part of the same body.
D. both 'b' & 'c'

Answer: Option B

Explanation:

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3. 

The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is

A. Nusselt number.
B. Sherwood number.
C. Schmidt number.
D. Stanton number.

Answer: Option C

Explanation:

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4. 

Finned tube heat exchangers

A. give larger area per tube.
B. use metal fins of low thermal conductivity.
C. facilitate very large temperature drop through tube wall.
D. are used for smaller heat load.

Answer: Option A

Explanation:

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5. 

The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.

A. increases
B. decreases
C. remains constant
D. may increase or decrease ; depends on the material

Answer: Option D

Explanation:

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