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This set of Refrigeration and Air conditioning Multiple Choice Questions & Answers (MCQs) focuses on Refrigeration And Air Conditioning Set 3
Q1 | Water is used as a refrigerant in
- Vapour absorption cycle
- Steam jet refrigeration
- Vapour absorption cycle
- Cascade system
- None of the above
Q2 | During adiabatic saturation process on unsaturated air
- Dry bulb temperature remains constant
- Wet bulb temperature remains constant
- Dew point temperature remains constant
- Relative humidity remains constant
- None of the above
Q3 | In a vapour compression refrigeration cycle, high head pressure is indicated which does not change even when compressor is stopped and allowed to cool. The probable cause may be
- High refrigerant charge
- Low refrigerant charge
- Air in the system
- High vapour pressure
- Any of the above
Q4 | A critical temperature is the temperature
- Below which gas is always liquefied
- Above which a gas will never be liquefied
- Below which a gas does not obey gas laws
- Above which a gas may explode
- None of the above
Q5 | A Salinometer
- Measure intensity of illumination
- Measures temperatures in cryogenic regions
- Measures solar radiation
- Measures sound level
- Measures density of brine
Q6 | In cooling towers the heat is dissipated mainly by
- Freezing
- Convection
- Radiation
- Conduction
- Evaporation
Q7 | Capacity of a domestic refrigerator is in the range
- 1 to 3 tonnes
- 7 to 10 tonnes
- 0.1 to 0.3 tonnes
- 3 to 5 tonnes
- 5 to 7 tonnes
Q8 | If a refrigerator is directly exposed to sun rays
- It will stop working
- The refrigerant will leak
- There will be less cooling effect
- Frost will be formed on cabinet surface
- (A) and (B) above
Q9 | A refrigerating system operates on the reversed Carnot cycle. The higher temperature of the refrigerant in the system is 40?C and the lower is - 15?C. The capacity is to be 10 tons. Neglecting all losses, the coefficient of performance of the system would be
- 2.67
- 3.75
- 9.41
- 4.69
- 7.36
Q10 | As warm air cools, its
- Relative humidity increases
- Relative humidity decreases
- There is no effect on moisture holding capacity
- Capacity to hold moisture increases
- Dew point occurs
Q11 | In a small vapour compression cycle using capillary tubing for expansion, if suddenly uncondensed vapours enter the tubing, the result will be
- Improved refrigerating capacity
- Loss in refrigerating capacity
- Supply of superheated vapour to compressor
- Choking of drier
- All of the above
Q12 | In which section of a vapour compression system, the refrigerant is generally in the form of a wet vapour?
- Condenser outlet
- Expansion valve
- Evaporator
- Compressor
- Condenser inlet
Q13 | In a vapour absorption system as compared to vapour compression system, the compressor is replaced by
- Receiver
- Expansion valve
- Evaporator
- Conderser
- Absorber and generator
Q14 | In a refrigerating system work done per kg of air is 20 kcal and heat extracted per kg of air is 25 kcal. The quantity of refrigerant used is 10 kg. The coefficient of performance of the system would be
- 0.8
- 12.5
- 5
- 8
- 1.25
Q15 | If a one ton refrigeration machine, the significance of term "One ton" is that
- One ton of water can be converted into ice
- One ton of ice when melts from and at 0?C in 24 hours the refrigeration effect equivalent to that
- One ton water can be stored at a time
- One ton is the total weight of equipment
- One ton of refrigerant is used
Q16 | The change in temperature resulting from a gas expanding from one constant pressure, with no heat transfer and no external work other than to maintain the constant pressure is known as
- Dalton's law of partial pressures
- Kinetic theory of gases
- Avogadro's hypothesis
- Joule - Thomoson effect
- Law of conservation of energy
Q17 | Anhydrous substance is
- Free of hydrogen and other chemicals containing hydrogen
- Dry substance
- Free of humidity
- Free of hydrogen
- Free of water especially water of crystallization
Q18 | No refrigerator using reversed Carnot cycle has been constructed because
- It is uneconomical
- It is less efficient
- It requires bulky machines
- 9.41
- Isentropic portions of cycle require low speeds whereas isothermal protuons require high speeds
Q19 | The statement: If a maximum of gases or vapours is enclosed in a container, each will exert its own pressure on the container entirely independent of the others and the total absolute pressure will be equal to the sum of the partial pressure exerted by each of the gases. This statement is known as
- Newton's law of gases
- Kinetic theory of gases
- Avogadro's hypothesis
- Fick's law
- Dalton's law of partial pressures.
Q20 | Defrosting of evaporators is done because
- Frosting increases refrigerating effect
- Frosting retards heat flow
- Frosting is undersirable
- Frosting obstructs flow of refrigerant
- Frosting may cause damage to equipment
Q21 | No liquid can exist as a liquid at
- 100?C
- Zero pressure
- Zero viscosity
- 0?C
- 10,000 m height above the surface of earth
Q22 | Dischloromono fluoroethane is
- Freon 11
- Freon 12
- Freon 21
- Freon 22
- None of the above
Q23 | In a refrigeration system, if the compressor short cycles, the probable cause could be
- Intermittent contact in electric control circuit
- Dirty or iced evaporator
- Lack of refrigerant
- Overchange of refrigerant
- Any of the above
Q24 | Reversed Carnot cycle assumes that all processes in the cycle are
- Non-flow only
- 10,000 m height above the surface of earth
- Transient flow
- Non flow or steady flow
- Steady flow only
Q25 | Which of the following valves is used on domestic refrigerators
- Solenoid valve
- Expansion valve
- Spring safety valve
- Wheel valve
- None of the above