Vapor Compression Cycle:
This is the thermodynamic cycle that is usually used in household refrigerators and air conditioning units. The basic theme is that you have to achieve cooling below 0 Celcius. If you are to make cooling above and near to 0 celcius, then you can make use of water evaporation (as water cooling fans are used) since evaporation causes cooling.
Vapor Compression cycle starts with a refrigerant (gas) which is
1) Compressed to increase it's pressure and hence temperature (since P is directly proportional to T) when passed through "compressor". This process takes place at constant entropy. The gas turns to superheated vapors.
2) This superheated vapors then passes through "condenser". The condenser removes the superheat and then removes the latent heat as well to bring it down to liquid form. The refrigerant is now at high pressure but at low temperature.
3) The refrigerant in condition of low temperature and high pressure is passed through a throttling valve (or through a nozzle) that causes a sudden pressure drop. This drop in pressure results in flash evaporation (since decreases in pressure decreases the boiling point) and hence a vapor-liquid mixture is formed.
4) This vapor-liquid mixture at very low temperature and pressure is now ready to transfer heat of the refrigerator. For that purpose it is passed through that chamber in which you have to bring heat transfer (here called "Evaporator"). After gaining heat of the warm air, the refrigerant (now at high temperature and at same low pressure) boils up and turn into vapor (gas) state. This vapor re-enters in compressor and the process continues.
All that just happened is the heat is transfer from low temperature area (the evaporator) to high temperature area (condenser), which is against the natural heat transfer gradient. Therefore, one have to apply energy for this transfer (the electrical energy transfer to the compressor). This conforms with the second law of thermodynamics. Click here for refrigerants and it's types.
This is the thermodynamic cycle that is usually used in household refrigerators and air conditioning units. The basic theme is that you have to achieve cooling below 0 Celcius. If you are to make cooling above and near to 0 celcius, then you can make use of water evaporation (as water cooling fans are used) since evaporation causes cooling.
Vapor Compression cycle starts with a refrigerant (gas) which is
1) Compressed to increase it's pressure and hence temperature (since P is directly proportional to T) when passed through "compressor". This process takes place at constant entropy. The gas turns to superheated vapors.
2) This superheated vapors then passes through "condenser". The condenser removes the superheat and then removes the latent heat as well to bring it down to liquid form. The refrigerant is now at high pressure but at low temperature.
3) The refrigerant in condition of low temperature and high pressure is passed through a throttling valve (or through a nozzle) that causes a sudden pressure drop. This drop in pressure results in flash evaporation (since decreases in pressure decreases the boiling point) and hence a vapor-liquid mixture is formed.
4) This vapor-liquid mixture at very low temperature and pressure is now ready to transfer heat of the refrigerator. For that purpose it is passed through that chamber in which you have to bring heat transfer (here called "Evaporator"). After gaining heat of the warm air, the refrigerant (now at high temperature and at same low pressure) boils up and turn into vapor (gas) state. This vapor re-enters in compressor and the process continues.
All that just happened is the heat is transfer from low temperature area (the evaporator) to high temperature area (condenser), which is against the natural heat transfer gradient. Therefore, one have to apply energy for this transfer (the electrical energy transfer to the compressor). This conforms with the second law of thermodynamics. Click here for refrigerants and it's types.
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