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Home Mechanical Engineering Heat Transfer, Refrigeration and Air Conditioning Comments

  • Question
  • The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called


  • Options
  • A. First law of thermodynamics
  • B. Newton's law of cooling
  • C. Newton's law of heating
  • D. Stefan's law

  • Correct Answer
  • Newton's law of cooling 


  • Heat Transfer, Refrigeration and Air Conditioning problems


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    • 1. It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be

    • Options
    • A. dehumidification
    • B. cooling and humidification
    • C. cooling and dehumidification
    • D. dehumidification and pure sensible cooling
    • Discuss
    • 2. The boiling point of R-12 is about - 30°C.

    • Options
    • A. True
    • B. False
    • Discuss
    • 3. In a parallel flow heat exchanger, the rate of flow of heat and the rate of decrease of temperature are maximum.

    • Options
    • A. Yes
    • B. No
    • Discuss
    • 4. The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called

    • Options
    • A. sub-cooling or under-cooling
    • B. super-cooling
    • C. normal cooling
    • D. none of these
    • Discuss
    • 5. The fluids used in electrolux refrigerator are

    • Options
    • A. water and hydrogen
    • B. ammonia and hydrogen
    • C. ammonia, water and hydrogen
    • D. none of these
    • Discuss
    • 6. The absolute humidity is the mass of water vapour present in 1 m3 of dry air.

    • Options
    • A. Agree
    • B. Disagree
    • Discuss
    • 7. In a lithium bromide absorption refrigeration system

    • Options
    • A. lithium bromide is used as a refrigerant and water as an absorbent
    • B. water is used as a refrigerant and lithium bromide as an absorbent
    • C. ammonia is used as a refrigerant and lithium bromide as an absorbent
    • D. none of the above
    • Discuss
    • 8. The thermostatic expansion valve is also called

    • Options
    • A. constant pressure valve
    • B. constant temperature valve
    • C. constant superheat valve
    • D. none of these
    • Discuss
    • 9. During sensible heating of air __________ decreases.

    • Options
    • A. wet bulb temperature
    • B. relative humidity
    • C. dry bulb temperature
    • D. specific humidity
    • Discuss
    • 10. The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as

    • Options
    • A. conduction
    • B. free convection
    • C. forced convection
    • D. radiation
    • Discuss


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