Chemical Engineering - Heat Transfer

21. 

Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately

A. 32
B. 37
C. 45
D. 50

Answer: Option A

Explanation:

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22. 

In a heat exchanger, floating head is provided to

A. facilitate cleaning of the exchanger.
B. increase the heat transfer area.
C. relieve stresses caused by thermal expansion.
D. increase log mean temperature gradient.

Answer: Option C

Explanation:

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23. 

Leidenfrost point is a term concerned with the

A. condensation of the saturated vapor on a cold surface.
B. concentration of a corrosive solution by evaporation.
C. heat transfer between two highly viscous liquids.
D. boiling of a liquid on a hot surface.

Answer: Option D

Explanation:

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24. 

A process stream of dilute aqueous solution flowing at the rate of10 Kg.s-1 is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s-1. A 1 - 1 shell and tube heat exchanger is available. The best arrangement is

A. counter flow with process stream on shell side.
B. counter flow with process stream on tube side.
C. parallel flow with process stream on shell side.
D. parallel flow with process stream on tube side.

Answer: Option A

Explanation:

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25. 

Heat produced when a steady state current, I passes through an electrical conductor having resistance, 'R' is

A. IR
B. I2R
C. IR2
D. I2R2

Answer: Option B

Explanation:

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