online exam on refrigeration and air conditioning - Set 18 - ObjectiveBooks

# Practice Test: Question Set - 18

1. 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, is called
(A) Humidity ratio
(B) Relative humidity
(C) Absolute humidity
(D) Degree of saturation

2. During dehumidification process, _________ remains constant.
(A) Wet bulb temperature
(B) Relative humidity
(C) Dry bulb temperature
(D) Specific humidity

3. Pressure of water vapour is given by
(A) 0.622 Pv/ (Pb - Pv)
(B) Î¼/[1 - (1 - Î¼) (Ps/Pb)]
(C) [Pv (Pb - Pd)]/ [Pd (Pb - Pv)]
(D) None of these

4. R-12 is generally preferred over R-22 in deep freezers since
(A) It has low operating pressures
(B) It gives higher coefficient of performance
(C) It is miscible with oil over large range of temperatures
(D) All of the above

5. In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is
(A) Heated and dehumidified
(B) Heated and humidified
(C) Cooled and humidified
(D) Cooled and dehumidified

6. A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called
(A) Automatic expansion valve
(B) High side float valve
(C) Thermostatic expansion valve
(D) Low side float valve

7. An infinite parallel planes with emissivities e₁ and e₂, the interchange factor for radiation from surface 1 to surface 2 is given by
(A) (e₁ + e₂)/ e₁ + e₂ - e₁e₂
(B) 1/e₁ + 1/e₂
(C) e₁ + e₂
(D) e₁e₂

8. The emissivity of a polished silver body is _________ as compared to black body.
(A) Same
(B) Low
(C) Very low
(D) High

9. Air refrigerator works on
(A) Reversed Carnot cycle
(B) Bell Coleman cycle
(C) Both (A) and (B)
(D) None of these

10. The relative coefficient of performance is equal to
(A) (Theoretical C.O.P.)/ (Actual C.O.P.)
(B) (Actual C.O.P.) /(Theoretical C.O.P.)
(C) (Actual C.O.P.) × (Theoretical C.O.P.)
(D) None of these

11. In case of sensible cooling of air, the coil efficiency is given by
(A) B.P.F. - 1
(B) 1 - B.P.F.
(C) 1/ B.P.F.
(D) 1 + B.P.F.

12. For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is
(A) Reciprocating
(B) Rotating
(C) Centrifugal
(D) Screw

13. The wet bulb temperature during sensible cooling of air
(A) Remains constant
(B) Increases
(C) Decreases
(D) None of these

14. A condenser of refrigeration system rejects heat at the rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system will be
(A) 1/4
(B) 1/3
(C) 3
(D) 4

15. A refrigerant with the highest critical pressure is
(A) R-11
(B) R-12
(C) R-22
(D) Ammonia

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