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Home Mechanical Engineering Heat Transfer, Refrigeration and Air Conditioning Comments

  • Question
  • 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

  • Correct Answer
  • minimum 


  • Heat Transfer, Refrigeration and Air Conditioning problems


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    • 1. During a refrigeration cycle, heat is rejected by the refrigerant in a

    • Options
    • A. compressor
    • B. condenser
    • C. evaporator
    • D. expansion valve
    • Discuss
    • 2. 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
    • 3. 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
    • Discuss
    • 4. 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
    • 5. In a refrigerating machine, heat rejected is __________ heat absorbed.

    • Options
    • A. equal to
    • B. less than
    • C. greater than
    • Discuss
    • 6. 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
    • 7. 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
    • 8. In case of solids, the heat transfer takes place according to radiation.

    • Options
    • A. Correct
    • B. Incorrect
    • Discuss
    • 9. Which of the following represents a heat pump?

    • Options
    • A.
    • B.
    • C.
    • D.
    • Discuss
    • 10. The condition of refrigerant after leaving the compressor and before entering the condenser is superheated vapour.

    • Options
    • A. Yes
    • B. No
    • Discuss


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