What is the air conditioner

How does air conditioning work?

If it is very hot, cooling is required. A fan and a cold towel around the neck can help to make ends meet. Air conditioning offers more comfort. From a physical point of view, it works in a very similar way to a refrigerator. Both devices transport thermal energy from a location with a lower temperature to a location with a higher temperature. On its own, however, heat only migrates in the direction of a lower temperature. That's why a trick is needed. It works with a refrigerant that is pumped through a closed circuit of tubes and is alternately in the liquid or gaseous state.

The air conditioning system works as follows: Liquid refrigerant flows into the building. On the way in, the pressure in the tube is reduced with the help of a throttle valve, which allows the refrigerant to expand. This lowers the temperature of the substance to below the air temperature inside the building. There then - on a meandering pipe and supported by a fan - there is an exchange of heat with the air. In this way, the indoor air in the building cools down while the refrigerant in the tube gradually warms up. Eventually it evaporates.

The now gaseous refrigerant leaves the interior of the building and enters a compressor. The gas is strongly compressed here. As a result, the molecules in it collide more often, causing the refrigerant to heat up even more. The temperature of the gas rises significantly above the temperature of the outside air. Outside the building, the refrigerant then releases the heat it has absorbed into the surrounding air. As a result, the refrigerant cools down and liquefies again. In the next step, the system feeds the liquid back into the building and the cycle starts all over again.

How an air conditioning system works

Both air conditioning and refrigerators are referred to as combined heat and power machines in physics. Because they transport heat with the help of mechanical energy - a compressor, a pump and fans - from a cold to a warmer reservoir. However, this principle only works if the interior remains closed. Air conditioning works poorly when the windows are open because warm air flowing in destroys the cooling effect.

Many air conditioning systems can not only lower the temperature, but also the humidity in the interior. Because when the temperature inside the building cools down, the humidity increases slowly. The reason: cool air can store less water vapor than warm air. The additional mechanism built into air conditioning systems is very simple. Water vapor from the air condenses into water droplets on the cool surface of the tubes through which the refrigerant flows. This condensed water is collected and discharged outside.

Various substances have been used as refrigerants for air conditioning systems and refrigerators over the years. Certain chlorinated hydrocarbons have now been banned because they attack the ozone layer. But the substitutes also have their pitfalls. For example, carbon dioxide is a greenhouse gas. The substitute propane does not damage the ozone layer or heat the climate, but it is flammable. The search for a refrigerant that is efficient, inexpensive and environmentally friendly therefore continues.