Refrigeration And Air Conditioning Set 6

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This set of Refrigeration and Air conditioning Multiple Choice Questions & Answers (MCQs) focuses on Refrigeration And Air Conditioning Set 6

Q1 | During air conditioning whenever two or more streams of moist air are mixed they follow
  • Isothermal process
  • Polytropic process
  • Constant pressure process
  • Polytropic process
  • Adiabatic process
Q2 | Air for air conditioning of aircraft cabin is obtained by
  • Compressing ambient air
  • Turbine exhaust
  • Bleeding from air compressor
  • Dehumidifying cabin air
  • Recycling cabin air
Q3 | Which of the following connections is usually not provided in a hermetically sealed type compressors?
  • Refrigerant inlet
  • Refrigerant outlet
  • Refrigerant charging connection
  • Lubricating oil charging connection
  • There is no connection provided
Q4 | In ammonia vapour compression system the temperature rise between the condenser outlet and the expansion valve should be
  • As high as possible to improve the performance
  • As high as possible to reduce motor power inputs
  • As little as possible for better performance
  • Anything as it has no bearing on the performance of system
  • None of the above
Q5 | The difference between the length of a certain brass rod and that of a steel rod is clamped to be constant at all temperatures". The above statement
  • can never be true
  • can be valid only for temperatures below 0?C
  • can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod
  • can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod
  • None of the above
Q6 | Ten grams of moisture per kg of dry air is removed from atmospheric air during air conditioning and the temperature becomes 30?C. If the atmospheric conditions are 40?C DBT and 60% Relative humidity, the RH of air after refrigeration would be
  • 50%
  • 69%
  • 40%
  • 104%
  • 60%
Q7 | PVC tubes are used for condenser and evaporator when the refrigerant is
  • Freon 12
  • Freon 22
  • Ammonia
  • Sulphur dioxide
  • None of the above
Q8 | Which reciprocating compressor is usually used in domestic refrigerators?
  • Open type
  • Semi-sealed type
  • Hermetically sealed type
  • Any of the above
  • None of the above
Q9 | A Carnot refrigerator extracts 100 kcal of heat per minute from a cold room which is maintained at - 15?C and it is discharged to atmosphere 30C?. The horse power required to run the unit would be
  • More than 6
  • 2 to 5
  • 5 to 6
  • 1.5 to 2
  • 1
Q10 | If space occupied by the refrigerating plant and cost is the major consideration, which of the following refrigerant will be preferred?
  • Carbondioxide
  • Sulphur dioxide
  • Mehtyl chloride
  • Ammonia
  • Any of the above
Q11 | When ammonia is the refrigerant, which of the following will be be the material for pipe through which refrigerant flows?
  • Cast steel or wrought iron
  • Copper
  • PVC
  • Brass
  • Aluminium
Q12 | Moisture in Freon refrigeration system causes
  • Ineffective refrigeration
  • Damage to compressor
  • High power consumption
  • Freezing of automatic regulating valve
  • None of the above
Q13 | Which of the following is not a desirable property of a refrigerant?
  • High critical temperature
  • Low specific heat of liquid
  • Low boiling point
  • High specific volume of air
  • All of the above
Q14 | A Carnot refrigerator operates between 300.3 K and 273 K. The fraction of cooling effect required as work input is
  • 20%
  • 10%
  • 50%
  • Not possible to find with the data
  • All of the above
Q15 | A thermometer in the compressor discharge line
  • Confirms the flow of refrigerant
  • Indicates the efficiency of cycle
  • Helps in adjusting the compressor performance
  • Shows the heat of refrigerant leaving the cylinder on way to the condenser
  • None of the above
Q16 | Freon 12 is a compound consisting of stoms of
  • Carbon, hydrogen and fluorine
  • Carbon and hydrogen
  • Carbon, hydrogen, fluorine and chlorine
  • Carbon, fluorine and chlorine
  • Carbon, hydrogen and oxygen
Q17 | During sensible of cooling of air
  • Wet bulb temperature decreases and relative humidity increases
  • Both wet bulb temperatures as well as relative humidity increase
  • Both humidity ratio as well as relative humidity remain constant
  • Both wet bulb temperature as well as relative humidity decrease
  • Wet bulb temperatures increases and relative humidity decreases
Q18 | The type of compressor used in refrigeration system is
  • Reciprocating
  • Centrifugal
  • Rotary sliding vane
  • Rotary screw compressor
  • All of the above
Q19 | In a refrigeration cycle the heat is rejected by refrigerant at
  • Evaporator
  • Condenser
  • Expansion valve
  • Compressor
  • All of the above
Q20 | 2 HP per ton of refrigeration is required to maintain the temperature of - 40?C in the refrigerator if the refrigeration cycle works on Carnot cycle. The COP of the cycle would be
  • 0.4
  • 1
  • 2.38
  • 5
  • 4.76
Q21 | An average adult while sitting in a cinema hall
  • Discharges about 100 kcal of heat per hour
  • Discards about 500 kcal of heat per hour
  • Absorbs about 500 kcal of heat per hour
  • Neither absorbs nor discards heat
  • Absorbs about 100 kcal of heat per hour
Q22 | During compression in a vapour compression cycle of the refrigerant is super heated
  • C.O.P. is reduced
  • C.O.P. is increased
  • Work done is reduced
  • Refrigerating effect is reduced
  • None of the above
Q23 | The heat removed capacity of a one ton refrigerator is
  • 100 kcal/4 hour
  • 100 kcal/hour
  • 50 kcal/min
  • 25 kcal/sec
  • None of the above
Q24 | A prssure gauge on the discharge side of compressor
  • Is mounted for show only
  • Indicates the temperature of refrigerant after compression
  • Gives a warning when the pressure reaches a dangerous point
  • Gives an ideas about the coefficient of performance of the cycle
  • Confirms the flow of refrigerant in cycle
Q25 | Major modification required to produce temperature of - 200?C in a vapour compression refrigeration system using Freon 12 as refrigerant, is
  • Condenser capacity must be increased to handle the refrigerant
  • Size of compressor required would be large to handle volumes of vapour
  • Compression ratio has to be restricted till stronger body of compressor is needed
  • Freon 12 cannot be used for such low temperatures
  • Insulation should be capable of withstanding such low temperatures