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Home Mechanical Engineering Heat Transfer, Refrigeration and Air Conditioning Comments

  • Question
  • The total radiation from a black body per second per unit area is __________ fourth power of the absolute temperature. This statement is known as Stefan-Boltzmann law.


  • Options
  • A. equal to
  • B. directly proportional to
  • C. inversely proportional to

  • Correct Answer
  • directly proportional to 


  • Heat Transfer, Refrigeration and Air Conditioning problems


    Search Results


    • 1. In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the refrigerants are respectively

    • Options
    • A. water and water
    • B. water and lithium bromide
    • C. ammonia and lithium bromide
    • D. ammonia and water
    • Discuss
    • 2. In a refrigerating machine, heat rejected is __________ heat absorbed.

    • Options
    • A. equal to
    • B. less than
    • C. greater than
    • Discuss
    • 3. The relative humidity is defined as

    • Options
    • A. the mass of water vapour present in 1 m3 of dry air
    • B. the mass of water vapour present in 1 kg of dry air
    • C. the ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure.
    • D. 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
    • Discuss
    • 4. Nusselt number (NN) is given by

    • Options
    • A.
    • B.
    • C.
    • D.
    • Discuss
    • 5. The wet bulb temperature lines, on the psychrometric chart, are curved lines.

    • Options
    • A. True
    • B. False
    • Discuss
    • 6. According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)

    • Options
    • A. Pb = pa - pv
    • B. Pb = pa + pv
    • C. Pb = pa x pv
    • D. Pb = pa/pv
    • Discuss
    • 7. During a refrigeration cycle, heat is rejected by the refrigerant in a

    • Options
    • A. compressor
    • B. condenser
    • C. evaporator
    • D. expansion valve
    • Discuss
    • 8. The critical radius is the insulation radius at which the resistance to heat flow is

    • Options
    • A. maximum
    • B. minimum
    • C. zero
    • D. none of these
    • Discuss
    • 9. In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

    • Options
    • A. Reynold's number
    • B. Grashoff's number
    • C. Reynold's number, Grashoff's number
    • D. Prandtl number, Grashoff's number
    • Discuss
    • 10. The humidity ratio or specific humidity is the mass of water vapour present in

    • Options
    • A. 1 m3 of wet air
    • B. 1 m3 of dry air
    • C. 1 kg of wet air
    • D. 1 kg of dry air
    • Discuss


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