Parts of the installation
A complete air conditioning system would include these parts:
There are installations that do not have all the components. A common example of a reduced installation is heating by radiators: it has thermal generation, primary transport (by water) and terminal devices that emit into the environment (radiators); but it does not treat the air, nor does it ventilate (it does not bring air to the premises).
For winter air conditioning, the most logical thing is to use a fuel boiler heating system that produces heat economically and from which hot water is brought to the air conditioners through pipes. And even better if the boiler is condensing.
A machine similar to the compression refrigeration machine can also be used, which works in reverse: taking heat from the cold, winter outside air and transferring it to the warmer inside air. In this case, the refrigeration machine is known as a heat pump. When outside temperatures are relatively mild, the performance of these devices is notable and compensates for the generally higher prices of the electrical energy used to drive the compressor, but on very cold days, with temperatures below 4°C, performance drops rapidly and quickly becomes very poor.
The so-called reversible generators also allow you to carry out the cycle indicated above for cooling and also for the heating process. A reversible generator extracts heat from cold air (whether outside or inside) and transfers it to warmer air (indoor or outside) depending on the seasons of the year. Therefore, the reversible generator constitutes a separate heating system and allows heating and cooling with the same device.
A system they call hybrid has recently appeared on the market, which has a boiler and a heat pump. An electronic control unit decides which of the two machines is started based on external conditions (heat pump performance) and energy prices, so that the most economical one works at all times.
Cooling can be done fundamentally by two means: by compression and by absorption. These two systems are based on the fact that they transport heat from a point with a lower energy level (the level is measured by temperature) to another with a higher level, and the medium generally used for this heat movement is a refrigerant.
Large refrigeration machines, known as water chillers, refrigeration plants, refrigeration equipment (or, in English, chiller), cool water that is then distributed to air conditioners through pipes. Larger refrigeration machines have better performance.
In the system known as split or multi-split, the heat transfer medium is the refrigerant liquid itself, which is taken to the evaporators of the terminals located in the premises to be air-conditioned. In this case, the refrigeration machine is compression.
Once the thermal energy is produced, it must be taken to the air treatment point (AUT) or to the terminals, using water through pipes (steel, copper or plastic materials). Sometimes also by means of cooling fluid.
Water can be carried through two, three or four pipe systems.
An air conditioner (in Spanish regulations, air treatment unit, UTA; in certain American countries, air handling unit, UMA, literal translation from English, which from a linguistic point of view is somewhat inappropriate since the verb manage implies using the hands and the processes are automatic), is the device in charge of treating the air in all its aspects and propelling it, either directly or through an air distribution network, to the premises to be air-conditioned. In principle, an air conditioner does not produce thermal energy, but rather receives it from specific heat and cold generators (boiler "Boiler (heating)") or refrigeration machine), although sometimes certain devices that produce cold (window air conditioners) are called air conditioners.
It consists of a series of elements that allow the various treatments that must be done to the air. A very complete UTA would consist of the devices listed and explained below, although not all air conditioners have all the parts:
Not all air conditioners have all the devices listed. Very often they only have the supply fan, especially those that only treat the ventilation air, without mixing with the return air. The post-heating battery is usually only used in systems that integrate heating or, in cooling, when the outside environment is very humid.
Transportation, here called secondary, consists of bringing thermal energy to the premises through treated air, through ducts from the treatment device (air conditioner).
The ducts can have a circular or rectangular section. They can be made of galvanized sheet metal, copper, fiberglass sheets and even plaster. It is an essential condition that the surfaces are smooth and easily cleanable, for which they must have cleaning records. As a general rule, air conditioning ducts must have adequate thermal insulation.
As a consequence of the latest European directives related to energy efficiency, air conditioning ducts must be as airtight as possible. The tightness levels are classified from level A, the lowest, to the maximum level D. The duct network is made up of a mixture of elements of different typology and shape that give the facilities an average level of tightness of type B. Building more tight ducts of level C would represent increasing their tightness threefold, contributing significantly to the energy improvement of the facilities and global energy maintenance.[4].
Sometimes it is used as a duct, especially in air return, the space above a false ceiling and even a hallway (plenum).
The emission is done through various types of discharge ports (grids, diffusers...) from the air transport ducts.
When it comes to air-water systems, in addition to the ventilation air (called primary air) treated in the air conditioner, fan coils (fan-coils) or inductors&action=edit&redlink=1 "Inductor (air conditioning) (not yet written)" are used as support.
If they are split systems (split or multi-split), the evaporators emit directly with a fan.
Finally, the blown air must be diffused throughout the room, so that it reaches the entire habitable volume, but this topic, "Air diffusion in rooms"), is so broad that it deserves a separate article.