Refrigeration And Air Conditioning Set 6 MCQs

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

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