Latest 100 Refrigeration & Air Conditioning Objective Questions
1.The condensing pressure due to the presence of non condemnable gases, as compared to that actually required for condensing temperatures without non condemnable gases,
will be higher
will be lower
will remain unaffected
may be higher or lower depending upon the nature of non condemnable gases
unpredictable.
ANSWER : : will be higher
2.The moisture in a refrigerant is removed by
evaporator
safety relief valve
dehumidifier
driers
expansion valve
ANSWER : : driers
3.Ammonia-absorption refrigeration cycle requires
very little work input
maximum work input
nearly same work input as for vapour compression cycle
zero work input
none of the above.
ANSWER : : very little work input
4.In vapour compression cycle, the condition of refrigerant is high pressure saturated liquid
after passing through the condenser
before passing through the condenser
after passing through the expansion or throttle valve
before entering the expansion valve
before entering the compressor.
ANSWER : : before entering the expansion valve
5.In vapour compression cycle, the condition of refrigerant is very wet vapour
after passing through the condenser
before passing through the condenser
after passing through the expansion or throttle valve
before entering the expansion valve
before entering the compressor.
ANSWER : : before entering the compressor.
6.Critical temperature is’ the temperature above which
a gas will never liquefy
a gas will immediately liquefy
water will evaporate
water will never evaporate
none of the above.
ANSWER : : a gas will never liquefy
7.Clapeyron equation is a relation between
temperature, pressure and enthalpy
specific volume and enthalpy
temperature and enthalpy
temperature, pressure, and specific volume
temperature, pressure, specific value and enthalpy.
ANSWER : : temperature, pressure, specific value and enthalpy.
8.A standard ice point temperature corresponds to the temperature of
water at 0�C
ice at – 4�C
solid and dry ice
mixture of ice, water and vapour under equilibrium conditions under NTP conditions
mixture of ice and water Under equilibrium conditions.
ANSWER : : mixture of ice and water Under equilibrium conditions.
9.In S.J. unit, one ton of refrigeration is equal to
210 kJ/min
21 kJ/min
420 kJ/min
840 kJ/min
105 kJ/min.
ANSWER : : 210 kJ/min
10.One ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice
in 1 hour
in 1 minute
in 24 hours
in 12 hours
in 10 hours.
ANSWER : : in 24 hours
11.In vapour compression cycle the condition of refrigerant is superheated vapour
after passing through the condenser
before passing through the condenser
after passing through the expansion or throttle valve
before [entering the expansion valve
before entering the compressor.
ANSWER : : before passing through the condenser
12.The boiling point of ammonia is
-100�C
-50�C
– 33.3�C
0�C
33.3�C.
ANSWER : : – 33.3�C
13.Clapeyron equation is applicable for registration at
saturation point of vapour
saturation point of liquid
sublimation temperature
triple point
critical point.
ANSWER : : saturation point of vapour
14.In vapour compression cycle the condition off refrigerant is dry saturated vapour
after passing through the condenser
before passing through the condenser
after passing through the expansion or throttle valve
before entering the expansion valve
before entering the compressor..
ANSWER : : before entering the compressor..
15.The vapour compression refrigerator employs the following cycle
Rankine
Carnot
Reversed Rankine
Brayton
Reversed Carnot.
ANSWER : : Reversed Carnot.
16.Vapour compression refrigeration is some what like
Carnot cycle
Rankine cycle
reversed Camot cycle
reversed Rankine cycle
none of the above.
ANSWER : : none of the above.
17.Allowable pressure on high-pressure side or ammonia absorption system is of the order of
atmospheric pressure
slightly above atmospheric pressure
2-4 bars
5-6 bars
7-10 bars.
ANSWER : : 5-6 bars
18.In vapour compression cycle, the condition of refrigerant is saturated liquid
after passing through the condenser
before passing through the condenser
after passing through the expansion throttle valve
before entering the expansion valve
before entering the compressor.
ANSWER : : after passing through the condenser
19.The refrigerant for a refrigerator should have
high sensible heat
high total heat
high latent heat
low latent heat
low sensible heat
ANSWER : : high latent heat
20.The relative coefficient of performance is
actual COP/theoretical COP
theoretical COP/actual COP
actual COP x theoretical COP
1-actual COP x theoretical COP
1-actual COP/theoretical COP.
ANSWER : : actual COP/theoretical COP
21.One ton refrigeration corresponds to
50 kcal/min
50 kcal/kr
80 kcal/min
80 kcal/hr
1000 kcal/day.
ANSWER : : 50 kcal/min
22.Which of the following cycles uses air as the refrigerant
Ericsson
Stirling
Carnot
Bell coleman
none of the above.
ANSWER : : Bell coleman
23.Critical pressure of a liquid is the pressure
above which liquid will remain liquid
above which liquid becomes gas
above which liquid becomes vapour
above which liquid becomes solid
at which all the three phases exist together.
ANSWER : : above which liquid will remain liquid
24.An important characteristic of absorption system of refrigeration is
noisy operation
quiet operation
cooling below 0�C
very little power consumption
its input only in the form of heating.
ANSWER : : quiet operation
25.Air refrigeration operates on
Carnot cycle
Reversed Carnot cycle
Rankine cycle
Erricson cycle
Brayton cycle.
ANSWER : : Brayton cycle.
26.In refrigerators, the temperature difference between the evaporating refrigerant and the medium being cooled should be
high, of the order of 25�
as low as possible (3 to 11�C)
zero
any value
none of the above.
ANSWER : : as low as possible (3 to 11�C)
27.Formation of frost on evaporator in refrigerator
results in loss of heat due to poor heat transfer
increases heat transfer rate
is immaterial
can be avoided by proper design
decreases compressor power.
ANSWER : : results in loss of heat due to poor heat transfer
28.Refrigeration in aeroplanes usually employs the following refrigerant
C02
Freon-11
Freon-22
Air
none of the above.
ANSWER : : Air
29.Highest temperature encountered in refrigeration cycle should be
near critical temperature of refrigerant
above critical temperature
at critica. temperature
much below critical temperature
could be anywhere.
ANSWER : : much below critical temperature
30.Accumulators should have adequate volume to store refrigerant charge at least
10%
25%
50%
75%
100%.
ANSWER : : 50%
31.In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is
less than 2 kg
more than or equal to 3.65 kg
more than 10 kg
there is no such consideration
pone of the above.
ANSWER : : more than or equal to 3.65 kg
32.Air refrigeration cycle is used in
domestic refrigerators
commercial refrigerators
air conditioning
gas liquefaction
such a cycle does not exist.
ANSWER : : gas liquefaction
33.Presence of moisture in a refrigerant affects the working of
compressor
condenser
evaparator
expansion valve.
heat transfer.
ANSWER : : expansion valve.
34.In a vapour compression cycle, the refrigerant immediately after expansion valve is
liquid
sub-cooled liquid
saturated liquid
wet vapour
dry vapour.
ANSWER : : wet vapour
35.The bank of tubes at the back of domestic refrigerator are
condenser tubes
evaporator tubes
refrigerant cooling tubes
capillary tubes
throttling device.
ANSWER : : condenser tubes
36.The value of COP in vapour compression cycle is usually
always less than unity
always more than unity
equal to unity
any one of the above
none of the above.
ANSWER : : always more than unity
37.Absorption system normally uses the following refrigerant
Freon-11
Freon-22
C02
S02
ammonia.
ANSWER : : ammonia.
38.One of the purposes of sub-cooling the liquid refrigerant is to
reduce compressor overheating
reduce compressor discharge tempera-ture
increase cooling effect
ensure that only liquid and not the vapour enters the expansion (throttling) valve
none of the above.
ANSWER : : ensure that only liquid and not the vapour enters the expansion (throttling) valve
39.The domestic refrigerator uses following type of compressor
centrifugal
axial
miniature sealed unit
piston type reciprocating
none of the above.
ANSWER : : piston type reciprocating
40.In a refrigeration system, heat absorbed in comparison to heat rejected is
more
less
same
more for small capacity and less for high capacity
less for small capacity and more for high capacity.
ANSWER : : less
41.For better COP of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be
small
high
euqal
anything
under some conditions small and under some conditions high.
ANSWER : : small
42.The COP of a domestic refrigerator
is less than 1
is more than 1
is equal to 1
depends upon the make
depends upon the weather conditions.
ANSWER : : is more than 1
43.Condensing temperature in a refrigerator is the temperature
of cooling medium
of freezing zone
of evaporator
at which refrigerant gas becomes liquid
condensing temperature of ice.
ANSWER : : at which refrigerant gas becomes liquid
44.The higher temperature in vapour compression cycle occurs at
receiver
expansion valve
evaporator
condenser discharge
compressor discharge.
ANSWER : : compressor discharge.
45.In a flooded evaporator refrigerator, an accumulator at suction of compressor is used to
collect liquid refrigerant and prevent it from going to compressor
detect liquid in vapour
superheat the vapour
collect vapours
increase refrigeration effect.
ANSWER : : collect liquid refrigerant and prevent it from going to compressor
46.Domestic refrigerator working on vapour compression cycle uses the following type of expansion device
electrically operated throttling valve
manually operated valve
thermostatic valve
capillary tube
expansion valve.
ANSWER : : capillary tube
47.The vapour pressure of refrigerant should be
lower than atmospheric pressure
higher than atmospheric pressure
equal to atmospheric pressure
could be anything
none of the above.
ANSWER : : higher than atmospheric pressure
48.At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant
decreases
increases
remains same
depends on other factors
none of the above.
ANSWER : : increases
49.If a heat pump cycle operates between the condenser temperature of +27�C and evaporator temperature of – 23�C, then the Carnot COP will be
0.2
1.2
5
6
10.
ANSWER : : 6
50.Choose the correct statement
A refrigerant should have low latent heat
If operating temperature of system is low, then refrigerant with low boiling point should be used
Precooling and subcooling bf refrigerant are same
Superheat and sensible heat of a. refrigerant are same
Refrigerant is inside the lubes in case of a direct-expansion chiller.
ANSWER : : If operating temperature of system is low, then refrigerant with low boiling point should be used
51.In vapour compression cycle using NH3 as refrigerant, initial charge is filled at
suction of compressor
delivery of compressor
high pressure side colse to receiver
low pressure side near receiver
anywhere in the cycle.
ANSWER : : high pressure side colse to receiver
52.Highest pressure encountered in a refrigeration system should be
critical pressure of refrigerant
much below critical pressure
much above critical pressure
near critical pressure
there is no such restriction.
ANSWER : : much below critical pressure
53.Pick up the correct statement about giving up of heat from one medium to other in ammonia absorption system
strong solution to weak solution
weak solution to strong solution
strong solution to ammonia vapour
ammonia vapour to weak solution
ammonia vapour to strong solution.
ANSWER : : weak solution to strong solution
54.One ton of the refrigeration is
the standard unit used in refrigeration problems
the cooling effect produced by melting 1 ton of ice
the refrigeration effect to freeze 1 ton of water at 0�C into ice at 0�C in 24 hours
the refrigeration effect to produce 1 ton of ice at NTP conditions
the refrigeration effect to produce 1 ton of ice in 1 hour time.
ANSWER : : the refrigeration effect to freeze 1 ton of water at 0�C into ice at 0�C in 24 hours
55.For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then
bigger cabinet should be used
smaller cabinet should be used
perfectly tight vapour seal should be used
refrigerant with lower evaporation temperature should be used
refrigerant with high boiling point must be used.
ANSWER : : perfectly tight vapour seal should be used
56.In vapour compression refrigeration system, refrigerant occurs as liquid between
condenser and expansion valve
compressor and evaporator
expansion valve and evaporator
compressor and condenser
none of the above.
ANSWER : : expansion valve and evaporator
57.If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be
same
more
less
more/less depending on rating
unpredictable.
ANSWER : : more
58.The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy-diagram represents
condensation of the refrigerant vapour
evaporation of the refrigerant liquid
compression of the refrigerant vapour
metering of the refrigerant liquid
none of the above.
ANSWER : : evaporation of the refrigerant liquid
59.One ton of the refrigeration is
the standard unit used in refrigeration problems
the cooling effect produced by melting 1 ton of ice
the refrigeration effect to freeze 1 ton of water at 0�C into ice at 0�C in 24 hours
the refrigeration effect to produce 1 ton of ice at NTP conditions
the refrigeration effect to produce 1 ton of ice in 1 hour time.
ANSWER : : the refrigeration effect to freeze 1 ton of water at 0�C into ice at 0�C in 24 hours
60.For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then
bigger cabinet should be used
smaller cabinet should be used
perfectly tight vapour seal should be used
refrigerant with lower evaporation temperature should be used
refrigerant with high boiling point must be used.
ANSWER : : perfectly tight vapour seal should be used
61.In vapour compression refrigeration system, refrigerant occurs as liquid between
condenser and expansion valve
compressor and evaporator
expansion valve and evaporator
compressor and condenser
none of the above.
ANSWER : : expansion valve and evaporator
62.If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be
same
more
less
more/less depending on rating
unpredictable.
ANSWER : : more
63.The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy-diagram represents
condensation of the refrigerant vapour
evaporation of the refrigerant liquid
compression of the refrigerant vapour
metering of the refrigerant liquid
none of the above.
ANSWER : : evaporation of the refrigerant liquid
64.Freon group of refrigerants are
inflammable
toxic
non-inflammable and toxic
non-toxic and inflammable
non-toxic and non-inflammable.
ANSWER : : non-toxic and non-inflammable.
65.The leaks in a refrigeration system using Freon are detected by
halide torch which on detection produces greenish flame lighting
sulphur sticks which on detection gives white smoke
using reagents
smelling
sensing reduction in pressure.
ANSWER : : halide torch which on detection produces greenish flame lighting
66.Super heating in a refrigeration cycle
increases COP
decreases COP
COP remains unaltered
other factors decide COP
unpredictable.
ANSWER : : decreases COP
67.Short horizontal lines on pressure-enthalpy chart show
constant pressure lines
constant temperature lines
constant total heat lines
constant entropy lines
constant volume lines.
ANSWER : : constant pressure lines
68.Efficiency of a Cornot engine is given as 80%. If the- cycle direction be reversed, what will be the value of COP of reversed Carnot cycle
1.25
0.8
0.5
0.25
none of the above.
ANSWER : : 0.25
69.A certain refrigerating system has a normal operating suction pressure of 10 kg/cm gauge and condensing pressure of about 67 kg/cm. The refrigerant used is
Ammonia
Carbon dioxide
Freon
Brine
Hydrocarbon refrigerant.
ANSWER : : Carbon dioxide
70.Where does the lowest temperature occur in a vapour compression cycle ?
condenser
evaporator
compressor
expansion valve
receiver.
ANSWER : : evaporator
71.Aqua ammonia is used as refrigerant in the following type of refrigeration system
compression
direct
indirect
absorption
none of the above.
ANSWER : : absorption
72.Which of the following is not a desirable property of a refrigerant
high triiscibility with oil
low boiling point
good electrical conductor
large latent heat
non-inflammable.
ANSWER : : good electrical conductor
73.On the pressure-enthalpy diagram, condensation and desuperheating is represented by a horizontal line because the process
involves no change in volume
takes place at constant temperature
takes place at constant entropy
takes place at constant enthalpy
takes place at constant pressure.
ANSWER : : takes place at constant pressure.
74.Mass flow ratio of NH3 in comparison to Freon-12 for same refrigeration load and same temperature limits is of the order of
1 : 1
1 : 9
9 : 1
1 : 3
3 : 1
ANSWER : : 1 : 9
75.rick up the incorrect statement
lithium bromide used in vapour absorption cycle is nonvolatile
lithium bromide plant can’t operate below 0�C
a separator is used in lithium bromide plant to remove the unwanted water vapour by condensing
concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator
weak solution in liquid heat exchanger gives up heat to the strong solution.
ANSWER : : a separator is used in lithium bromide plant to remove the unwanted water vapour by condensing
76.In a refrigeration cycle, the flow of refrigerant is controlled by
compressor
condenser
evaporator
expansion valve
all of the above.
ANSWER : : expansion valve
77.Vertical lines on pressure-enthalpy chart show constant
pressure lines
temperature lines
total heat lines
entropy lines
volume lines.
ANSWER : : total heat lines
78.The COP of a vapour compression plant in comparison to vapour absorption plant is
more
less
same
more/less depending on size of plant
unpredictable.
ANSWER : : more
79.Most of the domestic refrigerators work on the following refrigeration system
vapour compression
vapour absorption
carnot cycle
electrolux refrigerator
dual cycle.
ANSWER : : vapour compression
80.The C.O.P. of a refrigeration cycle with lowering of condenser temperature, keeping the evaporator temperature constant, will
increase
decrease
may increase or decrease depending on the type of refrigerant used
remain unaffected
unpredictable.
ANSWER : : increase
81.For obtaining high COP, the pressure range of compressor should be
high
low
optimum
any value
there is no such criterion.
ANSWER : : low
82.The C.O.P. of a domestic refrigerator in comparison to domestic air conditioner will be
same
more
less
dependent on weather conditions
unpredictable.
ANSWER : : less
83.Which of the following refrigerants has lowest freezing point
Freon-12
NH3
C02
Freon-22
S02.
ANSWER : : Freon-22
84.Reducing suction pressure in refrigeration cycle
lowers evaporation temperature
increases power required per ton of refrigeration
lowers compressor capacity because vapour is lighter
reduces weight displaced by piston
all of the above.
ANSWER : : all of the above.
85.The refrigeration effect in a dry evaporator compared to flooded evaporator in a similar plant is
same
more
less
more or less depending on ambient conditions
unpredictable.
ANSWER : : less
86.The advantage of dry compression is that
it permits higher speeds to be used
it permits complete evaporation in the evaporator
it results in high volumetric and mechanical efficiency
all of the above
none of the above.
ANSWER : : all of the above
87.The coefficient of performance is the ratio of the refrigerant effect to the
heat of compression
work done by compressor
enthalpy increase in compressor
all of the above
none of the above.
ANSWER : : all of the above
88.Under-cooling in a refrigeration cycle
increases COP
decreases COF
COP remains unaltered
other factors decide COP
unperdictable.
ANSWER : : increases COP
89.Choose the wrong statement
Temperature of medium being cooled must be below that of the evaporator
Refrigerant leaves the condenser as liquid
All solar thermally operated absorption systems are capable only of intermittent operation
frost on evaporator reduces heat transfer
refrigerant is circulated in a refrigeration system to transfer heat.
ANSWER : : Temperature of medium being cooled must be below that of the evaporator
90.The general rule for rating refrigeration systems (excepting for C02 system) is to approximate following h.p. per ton of refrigeration
0.1 to 0.5 h.p. per ton of refrigeration
0.5 to 0.8 h.p. per ton of refrigeration
1 to 2 h.p. per ton of refrigeration
2 to 5 h.p. per ton of refrigeration
5 to 10 h.p. per ton refrigeration.
ANSWER : : 1 to 2 h.p. per ton of refrigeration
91.The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.
more
less
equally.
unpredictable
none of the above.
ANSWER : : more
92.Cooling water is required for following equipment in ammonia absorption plant
condenser
evaporator
absorber
condenser and absorber
condenser, absorber and separator (rectifier).
ANSWER : : condenser, absorber and separator (rectifier).
93.Moisture in freon refrigeration system causes
ineffective refrigeration
high power consumption
freezing automatic regulating valve
corrosion of whole system
breakdown of refrigerant.
ANSWER : : freezing automatic regulating valve
95.The C.O.P of a refrigeration cycle with increase in evaporator temperature, keeping condenser temperature constant, will
increase
decrease
remain unaffected
may increase or decrease depending on the type of refrigerant used
unpredictable.
ANSWER : : increase
96.The evolution of heat of solution takes place in ammonia absorption plant when
ammonia vapour goes into solution
ammonia vapour is driven out of solution
lithium bromide mixes with ammonia
weak solution mixes with strong solution
lithium bromide is driven out of solution.
ANSWER : : ammonia vapour goes into solution