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Mechanical Engineering :: Heat Transfer,Refrigeration and Air Conditioning

  1. The expansion valve in a refrigerator controls the flow of refrigerant.

  2. A.
    Correct
    B.
    Incorrect

  3. The relative humidity lines on a psychrometric chart are

  4. A.
    vertical and uniformly spaced
    B.
    horizontal and uniformly spaced
    C.
    horizontal and non-uniformly spaced
    D.
    curved lines

  5. The C.O.P. of a heat pump working on a reversed Carnot cycle is


  6. A vapour absorption refrigeration system

  7. A.
    gives noisy operation
    B.
    gives quiet operation
    C.
    requires little power consumption
    D.
    cools below 0° C

  8. The rato of energy transferred by convection to that by conduction is called

  9. A.
    Stanton number
    B.
    Nusselt number
    C.
    Biot number
    D.
    Peclet number

  10. A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300 K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with cp = 1 kJ/kg)

  11. A.
    25 kJ/kg
    B.
    50 kJ/kg
    C.
    l00 kJ/kg
    D.
    125 kJ/kg

  12. Wet bulb temperature indicates the moisture content in air.

  13. A.
    Agree
    B.
    Disagree

  14. A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100° C and leaves at 60° C. A cold fluid enters the heat exchanger at 40° C. The mean temperature difference between the two fluids is

  15. A.
    20°C
    B.
    40°C
    C.
    60°C
    D.
    66.7°C

  16. The inclined and non-uniformly spaced straight lines on a psychrometric chart indicates wet bulb temperature.

  17. A.
    Agree
    B.
    Disagree

  18. The heat transfer by conduction through a thick cylinder(Q) is given by (where T1 = Higher temperature, T2 = Lower temperature, r1 = Inside radius, r2 = Outside radius, l = Length of cylinder, and k = Thermal conductivity)