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Home Mechanical Engineering Heat Transfer, Refrigeration and Air Conditioning Comments

  • Question
  • R-12 is generally preferred over R-22 in deep freezers since


  • Options
  • A. it has low operating pressures
  • B. it gives higher coefficient of performance
  • C. it is miscible with oil over large range of temperatures
  • D. all of the above

  • Correct Answer
  • it is miscible with oil over large range of temperatures 


  • Heat Transfer, Refrigeration and Air Conditioning problems


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    • 1. The refrigerant widely used in domestic refrigerators is

    • Options
    • A. ammonia
    • B. carbon dioxide
    • C. sulphur dioxide
    • D. R-12
    • Discuss
    • 2. The mass of water vapour present in 1 kg of dry air, is called humidity ratio.

    • Options
    • A. True
    • B. False
    • Discuss
    • 3. The unit of overall coefficient of heat transfer is

    • Options
    • A. W/m2K
    • B. W/m2
    • C. W/mK
    • D. W/m
    • Discuss
    • 4. The ratio of actual heat transfer to the maximum possible heat transfer is known as heat exchanger effectiveness.

    • Options
    • A. Agree
    • B. Disagree
    • Discuss
    • 5. The lowest thermal diffusivity is of

    • Options
    • A. iron
    • B. lead
    • C. aluminium
    • D. rubber
    • Discuss
    • 6. An infinite parallel planes with emissivities e1 and e2, the interchange factor for radiation from surface 1 to surface 2 is given by

    • Options
    • A.
    • B.
    • C. e1 + e2
    • D. e1e2
    • Discuss
    • 7. Hydrogen is used in electrolux refrigeration system so as to __________ the rate of evaporation of the liquid ammonia passing through the evaporator.

    • Options
    • A. equalise
    • B. reduce
    • C. increase
    • Discuss
    • 8. Which of the following statement is correct?

    • Options
    • A. In vapour absorption refrigerator, the compression of refrigerent is avoided.
    • B. Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.
    • C. In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.
    • D. all of the above
    • Discuss
    • 9. The cooling system used for supersonic aircrafts and rockets is

    • Options
    • A. simple air cooling system
    • B. boot-strap air cooling system
    • C. reduced ambient air cooling system
    • D. regenerative air cooling system
    • Discuss
    • 10. The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure, is called

    • Options
    • A. humidity ratio
    • B. relative humidity
    • C. absolute humidity
    • D. degree of saturation
    • Discuss


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