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
Correct Answer :
A. Increase
Related Questions
The difference between dry bulb temperature and wet bulb temperature, is called
Dry bulb depression
Wet bulb depression
Dew point depression
Degree of saturation
The relative humidity is defined as
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
For obtaining high COP, the pressure range of compressor should be
High
Low
Optimum
Any value
During sensible cooling of air ________ decreases.
Wet bulb temperature
Relative humidity
Dry bulb temperature
Specific humidity
In a vapour compression system, the condition of refrigerant is dry saturated vapour
Before entering the compressor
After leaving the compressor
Before entering the condenser
After leaving the condenser
Aqua ammonia is used as refrigerant in the following type of refrigeration system
Compression
Direct
Indirect
Absorption
The boiling point of ________ is 10.5°C.
Ammonia
R-12
Sulphur dioxide
Carbon dioxide
Reducing suction pressure in refrigeration cycle
Lowers evaporation temperature
Increases power required per ton of refrigeration
Lowers compressor capacity because vapour is lighter
All of the above
A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be
1.33
2.33
3.33
4.33
Where does the lowest temperature occur in a vapour compression cycle?
Condenser
Evaporator
Compressor
Expansion valve
The fluids used in Electrolux refrigerator are
Water and hydrogen
Ammonia and hydrogen
Ammonia, water and hydrogen
None of these
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
Freon group of refrigerants are
Inflammable
Toxic
Non-inflammable and toxic
Nontoxic and non-inflammable
The coefficient of performance of Heat Pump is always __________ one.
Equal to
Less than
Greater than
None of these
Highest pressure encountered in a refrigeration system should be
Critical pressure of refrigerant
Much below critical pressure
Much above critical pressure
Near critical pressure
The dry bulb temperature during sensible heating of air
Remains constant
Increases
Decreases
None of these
The leakage in a refrigeration system using ammonia is detected by
Halide torch
Sulphur sticks
Soap and water
All of these
The unit of thermal diffusivity is
m/hK
m/h
m²/h
m²/hK
The relative humidity lines on a psychrometric chart are
Vertical and uniformly spaced
Horizontal and uniformly spaced
Horizontal and non-uniformly spaced
Curved lines
The ratio of heat extracted in the refrigerator to the work-done on the refrigerant is called
Coefficient of performance of refrigeration
Coefficient of performance of heat pump
Relative coefficient of performance
Refrigerating efficiency
The freezing point of R-12 is
-86.6°C
-95.2°C
-107.7°C
-135.8°C
The relative coefficient of performance is equal to
(Theoretical C.O.P.)/ (Actual C.O.P.)
(Actual C.O.P.) /(Theoretical C.O.P.)
(Actual C.O.P.) × (Theoretical C.O.P.)
None of these
In a vapour compression cycle, the refrigerant immediately after expansion valve is
Liquid
Sub-cooled liquid
Saturated liquid
Wet vapour
A refrigerant with the highest critical pressure is
R-11
R-12
R-22
Ammonia
An important characteristic of absorption system of refrigeration is
Noisy operation
Quiet operation
Cooling below 0°C
Very little power consumption
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
Allowable pressure on high pressure side or ammonia absorption system is of the order of
Atmospheric pressure
Slightly above atmospheric pressure
24 bars
56 bars
A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with Cp = 1 kJ/kg)
25 kJ/kg
50 kJ/kg
100 kJ/kg
125 kJ/kg
Air conditioning means
Cooling
Heating
Dehumidifying
All of these
The higher temperature in vapour compression cycle occurs at
Receiver
Expansion valve
Evaporator
Compressor discharge