Air Conditioning
Air Conditioning
An Air conditioner is a device which modifies the air in such a way as to make it more favourable for us.
Objectives of the Air Conditioning System:-
1. Cooling the air inside the given area
2. Filtering the air to toxic and non-toxic impurities in the air
3. Reducing the humidity in air
Functioning of a Conventional Air Conditioner:-
The basic principle used in a Conventional Air Conditioner is Vapour Refrigerant Cycle.
Heat flows naturally from a hot to a colder body. In refrigeration system the opposite must occur i.e. heat flows from a cold to a hotter body. This is achieved by using a substance called a refrigerant, which absorbs heat and hence boils or evaporates at a low pressure to form a gas. This gas is then compressed to a higher pressure, such that it transfers the heat it has gained to ambient air or water and turns back (condenses) into a liquid. In this way heat is absorbed, or removed, from a low temperature source and transferred to a higher temperature source.
The process of air conditioning can be thermodynamically be represented by the following diagram:-
The main components of an Air Conditioning cycle are:-
1. Compressor
2. Condenser
3. Throttling Valve/ Expansion device
4. Evaporator
The following diagram depicts the Air conditioning cycle on a pressure enthalpy (P-h) curve:-
The Air Conditioning cycle can be broken down into the following:-
1 –2 Low pressure liquid refrigerant in the evaporator absorbs heat from its surroundings, usually air to be conditioned. During this process it changes its state from a liquid to a gas, and at the evaporator exit is slightly superheated.
2 – 3 The superheated vapor enters the compressor where its pressure is raised. There will also be a big increase in temperature, because a proportion of the energy input into the compression process is transferred to the refrigerant.
3 -4 The high pressure superheated gas passes from the compressor into the condenser. The initial part of the cooling process (3 – 3a) de-superheats the gas before it is then turned back into liquid (3a – 3b). The cooling for this process is usually achieved by using air or water. A further reduction in temperature happens in the pipe work and liquid receiver (3b – 4), so that the refrigerant liquid is sub-cooled as it enters the expansion device.
4 -1 The high-pressure sub-cooled liquid passes through the expansion device, which both reduces its pressure and controls the flow into the evaporator.
Disadvantages of using a conventional Air Conditioner:-
The main disadvantage of using a conventional Air Conditioner is the high power consumption.
Another major concern of using the conventional Air Conditioners is that it emits greenhouse gases and gases which deplete ozone layer like chlorofluorocarbons.
Solution:-
With such economic and environmental disadvantages the use of air conditioners doesn’t seem plausible. But given the high temperatures reached in summer the use of air conditioners becomes necessary.
One of the possible solutions to this problem is using the solar energy itself to counter with the heat produced by it. Given the amount of time the Sun shines and the intensity with which it does, it will not be wrong to say that the potential of solar energy being used is very high.
