How does an air conditioner cool the air?

Air conditioning functionality

How does air conditioning work?

Air conditioning systems ensure consistently pleasant temperatures, even when the barometer climbs up outside. High-quality full air conditioning systems can not only cool, they also regulate the humidity, clean the room air and ensure air exchange.

Many associate air conditioning with use in office buildings, where they not only enjoy a positive reputation. What is the use of air conditioning in private houses? For whom is air conditioning worthwhile and what should be considered?

We will deal with these questions in the following text. In the end, you should know more about how air conditioning systems work and how they are used in order to be able to make a decision for or against air conditioning.

How the air conditioning works

Often, only room air cooling is associated with an air conditioning system. According to the official definition, however, the air conditioning system and its components have the function of air treatment.

Larger, high-quality air conditioning systems not only change the air temperature, they also regulate the humidity, the quality of the air and the air speed. This means that they not only temper the room air, but also ventilate or ventilate it, filter the air and convey it. Smaller devices that are only equipped with a cooling function are called partial air conditioning systems.

Tip: If outside air is supplied to an air conditioning system, it also has a ventilation function. This is not the case with systems with circulating air.
  • Air-to-water air conditioners

    With this type of construction, the room air is partially tempered via water-bearing cooling systems such as radiators or cooling ceilings. The central device also cools the outside air supplied and is responsible for air conveyance, filtering, and humidification and dehumidification. The advantage of this design is the strong cooling capacity even with little air supplied.

  • Air-only air conditioners

    With this design, the room air is completely cooled using the supplied air. This is done in a central device.

As a rule, the air exchange in air conditioning systems works according to the circulating air principle and the rooms are not ventilated. If you also want to ventilate your building, you can combine the device with a ventilation system.

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Basic physical mechanisms

From a physical point of view, the air conditioning works in a similar way to a refrigerator. Thermal energy is transported from a place of low temperature to a place of higher temperature. However, heat only migrates on its own in the direction of a lower temperature.

A refrigerant is used to reverse this principle. This is pumped through a closed system and alternately kept in a liquid or gaseous state.

If the pressure on the liquid refrigerant is reduced, it expands and cools down to below the room air temperature. Supported by a fan, the room air is guided past a winding pipe with the refrigerant and the indoor air is thereby cooled.

At the same time, the refrigerant heats up and evaporates. It is fed from the building into a compressor. Here the gaseous refrigerant is strongly compressed so that it heats up. If the temperature rises above the temperature of the outside air, the heat is transferred to it. The refrigerant cools down again and liquefies. Now it is returned to the inside of the building and the cycle starts all over again.

Tip: A refrigerator works in a similar way to an air conditioning system and yet you cannot air-condition the interior with the refrigerator. This is due to the law of energy conservation, because a refrigerator only releases the heat that it has absorbed inside via the winding tubes on its back.

Different refrigerants are used

Today's refrigerants are no longer allowed to attack the ozone layer as previously used fluorocarbons (CFCs) did. These are banned in the meantime. However, even refrigerants used today can be very damaging to the environment if they are released. Carbon dioxide promotes the greenhouse effect, while propane is flammable - a refrigerant that is efficient and environmentally friendly does not yet exist.

Define the required cooling capacity

Before installing an air conditioning system, it is important that the required cooling capacity is precisely calculated. It is not only the size of the rooms that is decisive, the windows and the insulation of the roof, for example, have a major influence.

The following factors influence the cooling capacity of an air conditioning system:

  • window

    When there is strong sunlight, a lot of heat is introduced into the rooms via glass surfaces. Additional shading measures significantly reduce the heat input.

  • top, roof

    Roof surfaces can get very hot when exposed to sunlight. Without appropriate thermal insulation, this heat can enter the building unhindered. This heat input is greatly reduced with high-quality thermal insulation.

  • Internal heat input

    Many people and electrical devices give off heat. If a correspondingly large number of people are present in certain rooms and there are many heat-emitting devices in use, then the heat input is correspondingly high.

Additional functions of an air conditioning system

As mentioned above, many full air conditioning systems can do more than just cool the room air. Air conditioning systems reduce the humidity in the interior. This happens for a very simple reason: the cooled room air can store less water vapor than warm air. The room air is cooled down at the heat exchanger filled with refrigerant, where the water vapor from the air condenses into water droplets. An additional built-in mechanism collects the condensation and directs it to the outside. This dehumidification can be very pleasant on humid summer days, as the self-regulation of human body temperature is impaired in high humidity.

In addition, air conditioning can also filter the room air via the refrigeration machine. Filter fleeces are mostly used for this.

If you combine the air conditioning with a ventilation system, not only are cool interior temperatures guaranteed, but it is also automatically ventilated. This means that there is always a pleasant room climate, even when you are absent.

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