Superheating in a refrigeration cycle
Increases C.O.P
Decreases C.O.P
C.O.P remains unaltered
Other factors decide C.O.P
Correct Answer :
B. Decreases C.O.P
Related Questions
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
The wet bulb depression is zero when relative humidity is
Zero
0.5
0.75
1.0
Most of the domestic refrigerators work on the following refrigeration system
Vapour compression
Vapour absorption
Carnot cycle
Electrolux refrigerator
In Electrolux refrigerator
Ammonia is absorbed in hydrogen
Ammonia is absorbed in water
Ammonia evaporates in hydrogen
Hydrogen evaporates in ammonia
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 condition of refrigerant as it leaves the compressor in a vapour compression system is
Saturated liquid
Wet vapour
Dry saturated vapour
Superheated vapour
The cooling system used for supersonic aircrafts and rockets is
Simple air cooling system
Bootstrap air cooling system
Reduced ambient air cooling system
Regenerative air cooling system
The domestic refrigerator uses following type of compressor
Centrifugal
Axial
Miniature sealed unit
Piston type reciprocating
The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called
Wet bulb temperature
Dry bulb temperature
Dew point temperature
None of these
Short horizontal lines on pressure-enthalpy chart show
Constant pressure lines
Constant temperature lines
Constant total heat lines
Constant entropy lines
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
The human body feels comfortable when the heat stored in the body is
Positive
Negative
Zero
None of these
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
The specific humidity during heating and humidification process.
Remains constant
Increases
Decreases
None of these
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
Highest pressure encountered in a refrigeration system should be
Critical pressure of refrigerant
Much below critical pressure
Much above critical pressure
Near critical pressure
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 compressor
The capillary tube is not used in large capacity refrigeration systems because
Cost is too high
Capacity control is not possible
It is made of copper
Required pressure drop cannot be achieved
Cooling water is required for following equipment in ammonia absorption plant
Condenser
Evaporator
Absorber
Condenser, absorber and separator (rectifier)
The bypass factor of a cooling coil decreases with
Decrease in fin spacing and increase in number of rows
Increase in fin spacing and increase in number of rows
Increase in fin spacing and decrease in number of rows
Decrease in fin spacing and decrease in number of rows
The bypass factor (B. P. F.) in case of sensible heating of air is (Where td₁ = Dry bulb temperature of air entering the heating coil, td₂ = Dry bulb temperature of air leaving the heating coil, and td₃ = Dry bulb temperature of heating coil)
(td₂ - td₃)/(td₃ - td₁)
(td₃ - td₂)/(td₃ - td₁)
(td₃ - td₁)/(td₂ - td₃)
(td₃ - td₁)/(td₃ - td₂)
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, is called
Humidity ratio
Relative humidity
Absolute humidity
Degree of saturation
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
The thermostatic expansion valve is also called
Constant pressure valve
Constant temperature valve
Constant superheat valve
None of these
The sensible heat factor during cooling and dehumidification process is given by (where h₁ = Enthalpy of air entering the cooling coil, h₂ = Enthalpy of air leaving the cooling coil, and hA = Enthalpy of air at the end of dehumidification process)
(hA - h2)/ (h1 - h2)
(h2 - hA)/ (h1 - h2)
(h1 - h2)/ (hA - h2)
(hA - h1)/ (h2 - h1)
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
For obtaining high COP, the pressure range of compressor should be
High
Low
Optimum
Any value
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
The freezing point of sulphur dioxide is
-56.6°C
-75.2°C
-77.7°C
-135.8°C
In vapour compression refrigeration system, refrigerant occurs as liquid between
Condenser and expansion valve
Compressor and evaporator
Expansion valve and evaporator
Compressor and condenser