Just how do air conditioners work?
Find out how the air in your building was chilled to perfection, with our simple and scientific guide.
As you enjoy your cool, comfortable, climate-controlled surroundings, have you ever wondered how the air in your home or workplace is chilled to perfection? Just how do air conditioners work? The truth is surprisingly simple.
Hot air in, cool air out
Without interventions like air con and central heating, and depending on how effective your insulation is, the temperature in your building is at the mercy of the weather. So when the sun blazes down outside, the mercury indoors will start to rise, and you’ll begin to feel the effects of a hot and stuffy indoor environment. In order to reduce the ambient temperature and feel more comfortable, you need a way to get rid of the hot air in the room.
That’s where air conditioning comes in.
Different substances change their state from liquid to gas at different temperatures. For example, water turns to gas at 100 degrees Celsius, which is its boiling point. A refrigerant, such as carbon dioxide or ammonia, ‘boils’, or turns into gas, at a lower temperature than water – so when it comes into contact with the air in a typical building, it quickly gets warm enough to evaporate.
This theory of state changes is the fundamental principle behind how air conditioners work:
· Inside the air con unit, a refrigerant is pumped through valves by a component called the compressor, which (as the name suggests) compresses the refrigerant and makes it hot.
· The hot refrigerant gas then flows through to a condenser, which cools it down and turns it quickly back into its liquid state.
Changing the ambient temperature
When you set your thermostat to a temperature that’s cooler than current conditions, the air inside your building enters the AC unit through a grille, and comes into contact with the refrigerant in its liquid state – in a component called the evaporator. The warm air is absorbed by refrigerant liquid, which gets hotter until it evaporates (turns into gas). This also has the effect of removing moisture from the air.
The refrigerant gas then enters the compressor and gets hotter still, before being cooled in the condenser for the process to begin over again until enough warm air has been absorbed and cooled.
Meanwhile, the hot air absorbed by the system is pumped outside the building, and the cooled air is distributed back into the room.
Dehumidifying the air
Back in 1902, the first electrical air conditioning unit was invented by accident. Faced with the challenge of controlling the humidity in a printing plant (to preserve the colour quality of the ink), Willis Carrier stumbled upon a system that cooled down the atmosphere in order to reduce the moisture in the air. The lower temperature was a by-product of how the system worked – but the technology used to cool the air was adopted as the basis of modern air conditioning units. These
days, the air conditioning’s dehumidifying capabilities are seen as secondary to its main function – but a useful addition, nonetheless.