The bell-coleman refrigeration cycle uses …….as the working fluid
Hydrogen
Carbon dioxide
Air
Any inert gas
What would be the prime consideration in the design of refrigeration system of an air-craft?
High COP
Low work input per ton of refrigeration
Non-toxicity of the refrigerant
Low weight of the refrigeration equipment
In aircraft, air refrigeration cycle is used because of
High transfer rate
High COP
Availability of cold air at high altitudes
Low unit weight per ton of refrigeration
Fig. 13.3 shows the P-V plot of bell-coleman cycle of refrigeration. When compression and expansion are both isentropic, the coefficient of the machine is given by
Which aspect is not true in the context of a refrigerating machine working on Bell-Coleman cycle?
Low coefficient of performance
Simplicity of design and operation
High power consumption per ton of refrigeration
Large amount of air circulation per minute
All of the following statements about closed system of Bell-Coleman refrigeration cycle are correct, except
Air comes in direct contact with the space or substance being cooled
Less chances of choking of valves
Suction to the compression may be at high pressure
Size of the compressor and expander can be kept reasonably small
The vapour compression refrigeration cycle operates on reversed
Rankine cycle
Joule’s cycle
Atkinson cycle
Ericsson cycle
Which part of the vapour compression refrigeration cycle produces the refrigeration effect?
Condenser
Throttle valve
Evaporator
Compressor
During a refrigeration cycle based on vapour compression system, the highest temperature of the refrigerant occurs when the vapour leaves the
Condenser
Throttle valve
Evaporator
Compressor
/
1 and 2
2 and 3
1, 2 and 3
1, 2, 3 and 4
Absolute humidity of air-vapour mixture at a particular temperature is defined as
Mass of water vapour per kg of dry air in the mixture
Mass of water vapour per m3 of mixture
Mass of water vapour per kg of saturated air
Ratio of actual particle pressure of water vapour to the saturation pressure of water vapour at the same temperature
The humidity ratio or specific humidity of a given air-vapour mixture is
Mass of water vapour per kg of dry air in the mixture
Mass of water vapour per m3 of mixture
Mass of water vapour per m3 of dry air in the mixture
Mass of water vapour per kg of mixture
If ma=mass of dry air and mw=mass of water vapour in the air-water vapour mixture, then humidity ratio is given by
The humidity ratio of air is expressed by the relation
0.622
0.622
0.622
0.622
Where pw is partial pressure of water vapour, pa is partial pressure of dry air and p is the barometric pressure i.e.,total pressure of moist air
The humidity ratio of air is expressed by the relation =0.622 where p and pw are the barometric pressure and partial pressure of water vapour respectively. This identity is derived on the assumption that:
Only air behaves as a perfect gas
Both air and water vapour behave as perfect gas
Both air and water vapour behave as perfect gas but Dalton’s law of partial pressure is applied only to air
Both air and water vapour behave as perfect gas and obey the Dalton’s law of partial pressure
The equation =pv/ps (where pv=partial pressure of water vapour in moist air at a given temperature and ps=saturation pressure of water vapour at the same temperature is used to calculate:
Relative humidity
Specific humidity
Absolute humidity
Degree of saturation