The humidity ratio or specific humidity is the mass of water vapour present in
1 m3 of wet air
1 m3 of dry air
1 kg of wet air
1 kg of dry air
Correct Answer :
D. 1 kg of dry air
Related Questions
In a domestic refrigerator, a capillary tube controls the flow of refrigerant from the
Expansion valve to the evaporator
Evaporator to the thermostat
Condenser to the expansion valve
Condenser to the evaporator
In vapour compression cycle using NH₃ as refrigerant, initial charge is filled at
Suction of compressor
Delivery of compressor
High pressure side close to receiver
Low pressure side near receiver
One of the purposes of sub cooling the liquid refrigerant is to
Reduce compressor overheating
Reduce compressor discharge temperature
Increase cooling effect
Ensure that only liquid and not the vapour enters the expansion (throttling) valve
The freezing point of sulphur dioxide is
-56.6°C
-75.2°C
-77.7°C
-135.8°C
The central air conditioning system has ________ overall efficiency as compared to individual systems.
Same
Lower
Higher
None of these
During dehumidification process, __________ remains constant.
Wet bulb temperature
Relative humidity
Dry bulb temperature
Specific humidity
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
For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is
Reciprocating
Rotating
Centrifugal
Screw
Most thermostatic expansion valves are set for a superheat of
5°C
10°C
15°C
20°C
The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and
Carbon dioxide
Sulphur dioxide
Lithium bromide
R-12
Which of the following statement is wrong?
The performance of the vapour compression refrigerator varies considerably with both vaporising and condensing temperatures.
In vapour compression cycle, the useful part of the heat transfer is at the condenser.
In ammonia-hydrogen (Electrolux) refrigerator, no compressor, pump or fan is required.
The effect of under-cooling the liquid refrigerant is to decrease the coefficient of performance.
The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called
Sub-cooling or under-cooling
Super-cooling
Normal cooling
None of these
The comfort conditions in air conditioning are at (where DBT = Dry bulb temperature, and RH = Relative humidity)
25°C DBT and 100% RH
20°C DBT and 80% RH
22°C DBT and 60% RH
25°C DBT and 40% RH
Refrigeration in aeroplanes usually employs the following refrigerant
CO2
Freon-11
Freon-22
Air
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)
A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called
Dry air
Moist air
Saturated air
Specific humidity
For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of
Copper
Aluminium
Steel
Brass
Rick up the incorrect statement
Lithium bromide used in vapour absorption cycle is non volatile
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
During a refrigeration cycle, heat is rejected by the refrigerant in a
Compressor
Condenser
Evaporator
Expansion valve
The process, generally used in winter air-conditioning to warm and humidity the air, is called
Humidification
Dehumidification
Heating and humidification
Cooling and dehumidification
A vapour absorption refrigeration system
Gives noisy operation
Gives quiet operation
Requires little power consumption
Cools below 0°C
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
A one tonne refrigerating machine means that
One tonne is the total mass of machine
One tonne refrigerant is used
One tonne of water can be converted into ice
One tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min
For better C.O.P of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be
Small
High
Equal
Anything
The humidity ratio or specific humidity is the mass of water vapour present in
1 m3 of wet air
1 m3 of dry air
1 kg of wet air
1 kg of dry air
A thermostatic expansion valve in a refrigeration system
Ensures the evaporator completely filled with refrigerant of the load
Is suitable only for constant load systems
Maintains different temperatures in evaporator in proportion to load
None of the above
During cooling and dehumidification, dry bulb temperature
Remains constant
Increases
Decreases
None of these
During sensible cooling of air ________ decreases.
Wet bulb temperature
Relative humidity
Dry bulb temperature
Specific humidity
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
Which of the following statement is wrong?
The value of C.O.P. is always greater than one.
In a vapour compression system, the condition of refrigerant before entering the compressor is dry saturated vapour.
The space between the saturated liquid line and saturated vapour line, in a pressure enthalpy chart, is wet vapour region.
None of the above