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- Question
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
- Correct Answer
- 34.4
- 1. 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
- 2. 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
- 3. The steam ejector is used to
Options- A. remove condensate from the steam pipelines.
- B. create vacuum.
- C. superheat the steam.
- D. none of these. Discuss
- 4. When vaporisation takes place directly at the heating surface, it is called
Options- A. film boiling
- B. nucleate boiling
- C. vapour binding
- D. none of these Discuss
- 5. In a heat exchanger, floating head is provided to
Options- 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. Discuss
- 6. 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
- 7. 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
- 8. 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 Discuss
- 9. 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
- 10. 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
Heat Transfer problems
Search Results
Correct Answer: less than that of the uninsulated steam pipe.
Correct Answer: logarithmic mean temperature difference.
Correct Answer: create vacuum.
Correct Answer: nucleate boiling
Correct Answer: relieve stresses caused by thermal expansion.
Correct Answer: accounts for additional resistances to heat flow.
Correct Answer: increases
Correct Answer: Lewis relationship
Correct Answer: counter flow with process stream on shell side.
Correct Answer: decreases
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