Why doesn't air conditioning seem to work when plane is on the ground

                             Today we are discussing, how cooling is achieved in aircraft. For understanding the refrigeration system of aircraft, first, we have to understand the simple refrigeration system, which is basically used in the home. The refrigerator is a reversed heat engine which cools or maintain the temperature of a body lower than the atmosphere temperature. This is done by extracting the heat from a cold body and delivering it to the Hot body.


                             Refrigeration is the process of producing and maintaining the temperature below that of the surrounding atmosphere. simply, by removing heat from a substance under controlled condition. " Refrigeration is also produced by the method of dissolution of salts in water, When sodium chloride or calcium chloride are dissolved in water then they absorb heat and this property has been used to produce refrigeration. By this method, the temperature of the water can be lowered below 0 degrees centigrade, which is the freezing temperature of the water."


  • Simple Refrigeration system:-

                            Mechanical refrigeration is achieved by the system is Compressor, Evaporator, Expander, and Condenser.



  • During the process 1-2, The cold air from the refrigerator is drowned into the compressor cylinder where it is compressed in the compressor. Due to compression, both temperature and pressure increase. This step of refrigeration is known as a compression process.
  • During the process 2-3, The warm air from the compressor is passed through the condenser coil at constant pressure ( where its heat is liberated in the atmosphere). During this process, the temperature of warm air is reduced. If the condenser coil is placed inside a vessel that is filling with running water, then the heat of warm air is liberated in the water.
  • During the process 3-4, The air from the condenser is drawn into the expander where it is expanded and pressure drops and the temperature of the air during expansion also drop. This process is known as the expansion process.
  • During the process 4-1, The cold air from expander is passed to the refrigerator where it is expanded at the constant pressure and the temperature of air increases. Due to heat absorbed from the refrigerator.

  • Simple air refrigeration system:-
                               The simple air refrigeration system consists of the main compressor, a heat exchanger, a cooling turbine and a cooling fan.


  • In a simple air refrigeration system, the first ambient air is drawn to the main compressor where it is compressed, due to compression the pressure and temperature of air increases. Some of the amounts of this compressed air are drawn to the combustion chamber and remained air is sent to the heat exchanger.
  • This air is now passed through a coil in the heat exchanger, where the coil of a heat exchanger is surrounded by the ram air. there is the pressure drop in the heat exchanger, the temperature of air decreases. Heat rejected in the heat exchanger during the cooling process.

  • The cooled air is now expanded in the cooling turbine and sent to the cabin and cockpit where it is heated by the equipment and human, and ramed air from the heat exchanger is liberated to the atmosphere through the cooling fan, which is driven by the cooling turbine.

No comments