During heating and humidification, the final relative humidity of air
Can be lower or higher than that of the entering air
Is lower than that of the entering air
Is higher than that of the entering air
None of the above
Correct Answer :
A. Can be lower or higher than that of the entering air
Related Questions
At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant
Decreases
Increases
Remain same
Depends on other factors
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
In a refrigeration system, heat absorbed in comparison to heat rejected is
More
Less
Same
More for small capacity and less for high capacity
The pressure at the outlet of a refrigerant compressor is called
Suction pressure
Discharge pressure
Critical pressure
Back pressure
The bypass factor, in case of sensible cooling of air, is given by (where td₁ = Dry bulb temperature of air entering the cooling coil, td₂ = Dry bulb temperature of air leaving the cooling coil, and td₃ = Dry bulb temperature of the cooling coil)
(td₁ -td₃)/( td₂ -td₃)
(td₂ -td₃)/( td₁ -td₃)
(td₃ -td₁)/( td₂ -td₃)
(td₃ -td₂)/( td₁ -td₃)
The temperature of ammonia after compression in a vapour compression system is
20 to 50°C
50 to 70°C
70 to 110°C
None of these
Where does the lowest temperature occur in a vapour compression cycle?
Condenser
Evaporator
Compressor
Expansion valve
A refrigeration cycle operates between condenser temperature of + 27°C and evaporator temperature of -23°C. The Carnot coefficient of performance of cycle will be
0.2
1.2
5
6
The sensible heat factor during the heating and humidification process is given by (where h₁ = Enthalpy of air entering the heating coil, h₂ = Enthalpy of air leaving the heating coil, and hA = Enthalpy of air at the end of humidification process)
(hA - h2)/ (h1 - h2)
(h2 - hA)/ (h1 - h2)
(h1 - h2)/ (hA - h2)
(hA - h1)/ (h2 - h1)
The boiling point of carbon dioxide is
-20.5°C
-50°C
-63.3°C
-78.3°C
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
A Bell Coleman refrigerator working on dense air system as compared to open air system, for the same range of temperature, results in ________ power per tonne of refrigeration.
Same
Lower
Higher
None of these
Wet 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
Air refrigeration cycle is used in
Commercial refrigerators
Domestic refrigerators
Air-conditioning
Gas liquefaction
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
During humidification process, dry bulb temperature
Remains constant
Increases
Decreases
None of these
The suction pipe diameter of refrigerating unit compressor in comparison to delivery side is
Bigger
Smaller
Equal
Smaller/bigger depending on capacity
The thermostatic expansion valve is used in __________ type of evaporators.
Flooded
DX coil
Dry
None of these
During sensible cooling of air ________ decreases.
Wet bulb temperature
Relative humidity
Dry bulb temperature
Specific humidity
Presence of moisture in a refrigerant affects the working of
Compressor
Condenser
Evaporator
Expansion valve
In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is
High pressure saturated liquid
Wet vapour
Very wet vapour
Dry vapour
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
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
The leakage in a refrigeration system using ammonia is detected by
Halide torch
Sulphur sticks
Soap and water
All of these
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
The wet bulb temperature at 100% relative humidity is ________ dry bulb temperature.
Same as
Lower than
Higher than
None of these
In a vapour compression cycle, the refrigerant immediately after expansion valve is
Liquid
Sub-cooled liquid
Saturated liquid
Wet vapour
In Electrolux refrigerator
Ammonia is absorbed in hydrogen
Ammonia is absorbed in water
Ammonia evaporates in hydrogen
Hydrogen evaporates in ammonia
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
The value of C.O.P in vapour compression cycle is usually
Always less than unity
Always more than unity
Equal to unity
Any one of the above