The principles behind air conditioning and how air conditioning works is fairly straightforward and it is this principle which is captured, developed into a product and enables companies such as Carrier RentalXpress to provide air conditioning hire and air conditioning rental to clients across the South East of England and nationwide.

So, to run through Air Conditioning, this is how it works.

A refrigerant gas, of which there are many including R22 (which is due for phase out under the Montreal Protocol) is compressed to a high pressure. As a gas is compressed it gets hot (you might have noticed that when you pump up a bicycle tyre the pump gets hot as the pressure within the pump increases).

In an air conditioning hiret, the heat from the hot gas is expelled outside. This is done via the heat exchanger. Different air conditioning units use different systems and this heat removal could be achieved via a radiator such as a car radiator with a fan or maybe a cooling tower arrangement where the heat is transferred to cool water

and the water takes the heat outside and loses it either by dumping the water (total loss), or by evaporation, or a similar heat exchanger (the process of evaporation is very efficient at removing heat as you will have noticed when you sweat and a wind blows over the skin).

As the compressed gas cools, the refrigerant inside now liquefies. It is not cold, as it is most likely to be close to the ambient air temperature. It is also still at high pressure. This process of turning from a gas into a liquid is also known as condensing. Since this processes of condensing takes place with in the heat exchanger, it is often referred to as a condenser.

The now liquid (and still pressurised and cool) refrigerant is then cycled through the evaporator part of the air conditioning unit. Here the liquid is subject to a depressurisation, i.e. the liquid is squirted through a small gap into a larger space.

As the decompression takes place, the liquid evaporates and this process of evaporation requires energy.

This energy is taken as heat from the surrounding area and the area around the evaporator gets very cold. If air is blown across the evaporator then a cold blast can be maintained; if the air is recycled within the room then the room gets colder and colder until the temperature gradient between the chilled air and the evaporator surface is too low for any more heat to transfer.

Hence why, air conditioning is far more efficient if the windows are closed and the fresh air blowing across the evaporator gets progressively cooler. Once the liquid has evaporated, it is again compressed to a high pressure and the whole cycle starts again and the refrigerant is then sent back to the pump and the cycle continues until the air conditioning hire unit is turned off.

The main chilling limit is the heat transference between the evaporator and the air that it is chilling. But even if the surface area was large and the air flow great and the refrigerant evaporation plentiful there is a limit to how cool it goes. Eventually the room will be cold enough (assuming very well insulated) that the refrigerant will not evaporate.

The low pressure section of the evaporator may be trying to 'pull' the liquid to gas, but at a low enough temperature the refrigerant will stay as a liquid at normal atmospheric conditions No evaporation means no more heat absorption and no more possible drop in final temperature.

To find out more about air conditioning hire and rental, get in touch with one of the major suppliers of air conditioning units for the entire UK and most of Europe, Carrier Rental Xpress.