The COP of a vapour compression plant in comparison to vapour absorption plant is
More
Less
Same
More/less depending on size of plant
Correct Answer :
A. More
Related Questions
The C.O.P. of an absorption type refrigerator is given by (where T₁ = Temperature at which the working substance receives heat, T₂ = Temperature of cooling water, and T₃ = Evaporator temperature)
[T₁ (T₂ - T₃)] / [T₃ (T₁ - T₂)]
[T₃ (T₁ - T₂)]/ [T₁ (T₂ - T₃)]
[T₁ (T₁ - T₂)] / [T₃ (T₂ - T₃)]
[T₃ (T₂ - T₃)] / [T₁ (T₁ - T₂)]
Chaperon equation is applicable for registration at
Saturation point of vapour
Saturation point of liquid
Sublimation temperature
Triple point
The boiling point of ammonia is
100°C
50°C
33.3°C
0°C
Where does the lowest temperature occur in a vapour compression cycle?
Condenser
Evaporator
Compressor
Expansion valve
Degree of saturation or percentage humidity is
The mass of water vapour present in 1 m³ of dry air
The mass of water vapour present in 1 kg of dry air
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.
The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure
During sensible cooling of air, specific humidity
Remains constant
Increases
Decreases
None of these
The general rule for rating refrigeration systems (excepting for CO₂ 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
The reciprocating refrigerant compressors are very suitable for
Small displacements and low condensing pressures
Large displacements and high condensing pressures
Small displacements and high condensing pressures
Large displacements and low condensing pressures
Which of the following statement is correct?
In vapour absorption refrigerator, the compression of refrigerant is avoided.
Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.
In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.
All of the above
Dry bulb temperature is the temperature of air recorded by a thermometer, when
It is not affected by the moisture present in the air
Its bulb is surrounded by a wet cloth exposed to the air
The moisture present in it begins to condense
None of the above
The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure, is called
Humidity ratio
Relative humidity
Absolute humidity
Degree of saturation
A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called
Automatic expansion valve
High side float valve
Thermostatic expansion valve
Low side float valve
Mass flow ratio of NH₃ in comparison to Freon12 for same refrigeration load and same temperature limits is of the order of
1 : 1
1 : 9
9 : 1
1 : 3
Air refrigeration cycle is used in
Commercial refrigerators
Domestic refrigerators
Air-conditioning
Gas liquefaction
If a gas is to be liquefied, its temperature must be
Increased to a value above its critical temperature
Reduced to a value below its critical temperature
Equal to critical temperature
None of the above
Nusselt number (NN) is given by
NN = hl/k
NN = μ cp/k
NN = ρ V l /μ
NN = V²/t.cp
The process, generally used in summer air conditioning to cool and dehumidify the air, is called
Humidification
Dehumidification
Heating and humidification
Cooling and dehumidification
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
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
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
The emissivity of a polished silver body is __________ as compared to black body.
Same
Low
Very low
High
A refrigerant with the highest critical pressure is
R-11
R-12
R-22
Ammonia
The leakage in a refrigeration system using Freon is detected by
Halide torch
Sulphur sticks
Soap and water
All of these
The specific humidity during dehumidification process
Remains constant
Increases
Decreases
None of these
R-12 is generally preferred over R-22 in deep freezers since
It has low operating pressures
It gives higher coefficient of performance
It is miscible with oil over large range of temperatures
All of the above
During sensible heating of air _________ decreases.
Wet bulb temperature
Relative humidity
Dry bulb temperature
Specific humidity
The operating pressure for refrigerating units using R-12 as a refrigerant is
2 bar
8 bar
15 bar
30 bar
The superheating in a refrigeration cycle
Does not alter C.O.P.
Increases C.O.P.
Decreases C.O.P.
None of these
Rating of a domestic refrigerator is of the order of
0.1 ton
5 tons
10 tons
40 tons
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
1/4
1/3
3
4