How Does An Air Conditioning Unit Work?

June 15 2022

James Patten


We’ve all seen the large white boxes on the outside of properties and all felt the cooling effects of an air conditioning system on a hot summer’s day but have you ever stopped to think how that air conditioning system actually works?

It’s Chemistry!

Grab your white coat and safety goggles because to really know how an air conditioning unit works means a trip back to your chemistry lessons. 

First things first, there are 4 main components needed to make an air conditioning unit successfully cool a stuffy room or office. Those key players are a compressor, a condenser, an expansion valve and an evaporator.  In combination with some clever science you’ll also need coolant/refrigerant, a pump, pipes and fans.  

For the technical part, let’s get the highly skilled and trained expert from Heritage Heating & Cooling Ltd to explain: 

“The fundamental idea of an air conditioner is that it extracts heat from a room within your house or office and then pumps cool air back in. To do this, a standard air conditioner contains two fans, one attached to the outside of the building and the other to the inside, with an axle connecting the two, as well as a pump, an evaporation valve, a condensing coil and an evaporating coil.                                    

When the air conditioner is active, the pump condenses the coolant within the pipes of the air conditioning system. This passes through the condensing coil, which expels heat to the outside. The coolant then reaches the evaporation valve, where it does exactly what it says – it evaporates. Because evaporation results in a decrease in pressure, this leads to a decrease in temperature, so long as the occupied volume is the same on either side of the valve. The coolant is now a gas and flows to the evaporating coil, where it cools warm air coming in and expels cooler air. The coolant gas then returns to the pump and the cycle continues. The air flowing through the outside fan drives the axle which is connected to the inside fan, which completes the air conditioning process.”

Blue sky thinking turns green

As with all our energy systems we are trying to advance the air conditioning system offering in order to make the systems that we use to be more efficient, and less of a strain on the environment. When we look back over history our methods to cool our homes and workplaces have advanced along with developments in science. 

The 18th and 19th centuries saw Benjamin Franklin use the principle of evaporation to cool an object, whereas a century later John Gorrie used compression technology to turn water into ice. Michael Faraday worked with compressing certain chemicals to cool a liquid, which was eventually used to develop the first mechanical ice-machines. After this and by including axles with fans attached to encourage consistent air flow, the first modern-day air conditioner was invented and the rest is, indeed, history. Mechanical cooling was the start of the air conditioning process before advancements saw the introduction of refrigeration as we know it in today’s air conditioning systems.

Today technology is advancing with the introduction of evaporative cooling systems which do not use any refrigerant chemicals which is a huge tick in the sustainability box (they are 90% more energy efficient), however they aren’t quite so effective in humid climates so the technology advancement is now continuing towards a magnetic refrigeration route.

The future’s magnetic.

The aim of all new cooling systems will be to target the removal of harmful CFCs and HFCs (carbons which destroy the earth’s ozone layer) within the appliances that we use on a daily basis. Back to our Heritage Heating & Cooling Ltd’s resident expert “A new technology, known as magnetic air conditioning, which uses an effect known as the magnetocaloric effect involves a metal which is present within a magnetic field. The idea is that when the metal is placed into the field, it heats up and then loses the thermal energy, meaning that it is cooler than when it entered the magnetic field. In the future, we will most likely see these types of cooling units, especially since it will be safer, more efficient, and more environmentally friendly compared to any other type of cooling unit used previously.”

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