Heat Transfer problems
- 1. 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
Correct Answer: 34.4
- 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
Correct Answer: accounts for additional resistances to heat flow.
- 3. 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
Correct Answer: increases
- 4. 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
Correct Answer: Lewis relationship
- 5. 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
Correct Answer: counter flow with process stream on shell side.
- 6. 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
Correct Answer: decreases
- 7. 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
Correct Answer: both (b) and (c).
- 8. 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
Correct Answer: none of these.
- 9. 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
Correct Answer: mercury
- 10. Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.
Options- A. laminar
- B. transition
- C. both 'a' & 'b'
- D. highly turbulent Discuss
Correct Answer: highly turbulent
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