Refrigeration and air conditioning objective type questions and answers - Set 11

Practice Test: Question Set - 11


1. The advantage of dry compression is that
    (A) It permits higher speeds to be used
    (B) It permits complete evaporation in the evaporator
    (C) It results in high volumetric and mechanical efficiency
    (D) All of the above

2. The specific humidity during dehumidification process
    (A) Remains constant
    (B) Increases
    (C) Decreases
    (D) None of these

3. The C.O.P. of a refrigeration cycle with lowering of condenser temperature, keeping the evaporator temperature constant, will
    (A) Increase
    (B) Decrease
    (C) May increase or decrease depending on the type of refrigerant used
    (D) Remain unaffected

4. The alignment circle is marked on the psychrometric chart at
    (A) 20°C DBT and 50% RH
    (B) 26°C DBT and 50% RH
    (C) 20°C DBT and 60% RH
    (D) 26°C DBT and 60% RH

5. A refrigeration cycle operates between condenser temperature of + 27°C and evaporator temperature of -23°C. The Carnot coefficient of performance of cycle will be
    (A) 0.2
    (B) 1.2
    (C) 5
    (D) 6

6. Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and μ = Degree of saturation)
    (A) 0.622 Pv / (Pb - Pv)
    (B) μ/[1 - (1 - μ) (Ps/Pb)]
    (C) [Pv (Pb - Pd)]/ [Pd (Pb - Pv)]
    (D) None of these

7. In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is
    (A) Less than 2 kg
    (B) More than or equal to 3.65 kg
    (C) More than 10 kg
    (D) There is no such consideration

8. During sensible cooling,
    (A) Relative humidity remains constant
    (B) Wet bulb temperature increases
    (C) Specific humidity increases
    (D) Partial pressure of vapour remains constant

9. Choose the wrong statement
    (A) Temperature of medium being cooled must be below that of the evaporator
    (B) Refrigerant leaves the condenser as liquid
    (C) All solar thermally operated absorption systems are capable only of intermittent operation
    (D) Frost on evaporator reduces heat transfer

10. The superheating in a refrigeration cycle
    (A) Does not alter C.O.P.
    (B) Increases C.O.P.
    (C) Decreases C.O.P.
    (D) None of these

11. Refrigeration in aeroplanes usually employs the following refrigerant
    (A) CO2
    (B) Freon-11
    (C) Freon-22
    (D) Air

12. The condition of refrigerant as it leaves the compressor in a vapour compression system is
    (A) Saturated liquid
    (B) Wet vapour
    (C) Dry saturated vapour
    (D) Superheated vapour

13. The coefficient of performance is the ratio of the refrigerant effect to the
    (A) Heat of compression
    (B) Work done by compressor
    (C) Enthalpy increase in compressor
    (D) All of the above

14. The bypass factor (B. P. F.) in case of sensible heating of air is (Where td = Dry bulb temperature of air entering the heating coil, td = Dry bulb temperature of air leaving the heating coil, and td = Dry bulb temperature of heating coil)
    (A) (td₂ - td₃)/(td₃ - td₁)
    (B) (td₃ - td₂)/(td₃ - td₁)
    (C) (td₃ - td₁)/(td₂ - td₃)
    (D) (td₃ - td₁)/(td₃ - td₂)

15. Air refrigeration operates on
    (A) Carnot cycle
    (B) Reversed Carnot cycle
    (C) Rankine’s cycle
    (D) Brayton cycle

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