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- Question
Which of the following is concerned with both heat and mass transfer?
Options- A. Lewis relationship
- B. Nusselt number
- C. Kutateladze number
- D. Froude number
- Correct Answer
- Lewis relationship
- 1. With increase in temperature, the thermal conductivity of non-metallic amorphous solids
Options- A. decreases
- B. increases
- C. remains constant
- D. first decreases upto certain temperature and then increases Discuss
- 2. Fouling factor
Options- A. is a dimensionless quantity.
- B. does not provide a safety factor for design.
- C. accounts for additional resistances to heat flow.
- D. none of these. Discuss
- 3. In Joule's experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms-2. Neglecting the heat capacity of agitator, the temperature of water (in °C) is
Options- A. 40.5
- B. 34.4
- C. 26.8
- D. 25 Discuss
- 4. A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be
Options- A. greater than that for uninsulated steam pipe.
- B. less than that of the uninsulated steam pipe.
- C. equal to that of the uninsulated steam pipe.
- D. less than the steam pipe with 5 cms insulation. Discuss
- 5. In the equation Q = UA?t; ?t is
Options- A. geometric mean temperature difference.
- B. arithmetic mean temperature difference.
- C. logarithmic mean temperature difference.
- D. the difference of average bulk temperatures of hot and cold fluids. Discuss
- 6. 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
Options- 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. Discuss
- 7. With increase in porosity, the thermal conductivity of a solid substance
Options- A. increases
- B. decreases
- C. remains unchanged
- D. may increase or decrease; depends on the solid Discuss
- 8. Heat waves
Options- A. can not pass through vacuum.
- B. travel in straight line.
- C. can be reflected by a mirror.
- D. both (b) and (c). Discuss
- 9. Presence of a non-condensing gas in a condensing vapour
Options- A. increases the rate of condensation.
- B. decreases thermal resistance.
- C. is desirable to increase the film co-efficient.
- D. none of these. Discuss
- 10. Which of the following is not used as a medium for high temperature heating?
Options- A. Dowtherm
- B. mercury
- C. liquid metal (e.g. molten sodium)
- D. fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3) Discuss
Heat Transfer problems
Search Results
Correct Answer: increases
Correct Answer: accounts for additional resistances to heat flow.
Correct Answer: 34.4
Correct Answer: less than that of the uninsulated steam pipe.
Correct Answer: logarithmic mean temperature difference.
Correct Answer: counter flow with process stream on shell side.
Correct Answer: decreases
Correct Answer: both (b) and (c).
Correct Answer: none of these.
Correct Answer: mercury
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