Basic Theory of Air Conditioning

When a fluid is heated (cooled) it absorbs (emits) a certain amount of heat. When these processes produce a change in status, for example from liquid to gas (evaporation) or from gas to liquid (condensation), the amount of heat exchanged with the external source is significantly higher (vaporisation heat/condensation). An AC supply exploits this feature in two distinct phases:

  1. Passive Phase: In this phase, the fluid (gas) is compressed and condenses, there is therefore a consumption of energy (EE) and a release of heat to the outside cooling air.
  2. Active Phase: In this phase the same fluid (liquid) expands and evaporates, there is therefore an absorption of heat at the expense of the air inside the environments which consequently release heat and cool down.

In order to be applicable within the air conditioned areas, these two phases must take place at relatively low temperatures. The figure below shows the evaporation of the cooling liquid inside the coil generated by gas which is heated by ambient air which subsequently cools.