air condition
Air conditioning (denoted by the abbreviation AC from the English air conditioning) is the modification of the quality parameters of the air in closed spaces or a device (a system of devices) for such modification and distribution of such modified air. The main feature of air conditioning is the regulation of air temperature and humidity, which distinguishes it from ventilation, which only ensures the exchange of fresh air.
Air conditioning is sometimes necessary, for example in hospitals, some trains or some types of mines.
The principle
Cooling circuit diagram:
1. condenser 2. expansion valve 3. evaporator 4. compressor
To create thermal comfort in the room, the air conditioner uses the principle of a cooling circuit, which consists of the following events:
compression
liquefaction (condensation)
evaporation
In the 1st phase, the vapors of the cooling medium are brought to the compressor, where they are compressed (and, as a result of the compression, also heated).
In the 2nd phase, the cooling medium at high temperature and pressure is brought to the exchanger - condenser, where it is cooled by the surrounding air (the medium condenses). The released heat is removed to the outside space by a fan.
In the 3rd phase, the liquid is transported through a capillary, or an expansion valve, behind which the pressure and thus the temperature drop sharply. The medium continues to the next exchanger - the evaporator. The liquid starts to evaporate, taking heat from the evaporator space, usually a cooled room. A fan located near the evaporator is used to distribute cold air into the room. Then the refrigerant in gaseous state is fed to the compressor and the cycle repeats.
By turning the refrigerant flow in the system using the four-way valve, the evaporator and the condenser are exchanged, allowing the indoor unit in the condenser to transfer heat and thus heat the room.
Device types
Split systems
Split air conditioning systems, intended for one room, consist of a separate condenser with a compressor located in the outdoor environment and an indoor unit that contains an evaporator. They are connected to each other by a copper insulated pipe that carries the cooling medium.
MultiSplit systems
MultiSplit air conditioning systems intended for several rooms (usually 2 to 5), consist of a separate condenser with a compressor located in the outdoor environment and several indoor units that contain evaporators. Each indoor unit is connected to the outdoor unit by a copper insulated pipe that carries the cooling medium. Each indoor unit is individually controlled by its own controller, but all indoor units run in the same mode (cooling or heating).
Twin, Tripple a DoubleTwin systémy
If the room is large or highly divided, it is possible to use the Split system, in which the cooling power of the indoor unit is divided into two, three or up to four indoor units, which ensures a more even distribution of cold or heat in the room. The connecting pipe leading from the outdoor unit is divided into several branches in the room in hubs (refnets) and the indoor units are connected to it. All indoor units have a common controller and work at the same time with the same parameters and settings.
Mobile
Mobile split air conditioning
A mobile split system consists of an indoor unit on wheels connected by flexible pipes to an outdoor unit, similar to fixed split systems.
Mobile hose air conditioner
The entire air conditioner consists of one unit on wheels, which contains both a condenser and an evaporator. The discharge of air heated by the condenser is provided by a fan, which is connected to a hose that must be led to the outside environment. The disadvantage of this type of air conditioning is its reduced efficiency, because it uses air from the air-conditioned room to cool the condenser. Another disadvantage is that this type of air conditioning constantly pumps air out of the room, thereby creating a negative pressure that causes non-conditioned air to enter the room.
There are also mobile air conditioners with two hoses that solve these disadvantages. The second hose serves to supply air from the outside environment for cooling the condenser. At the same time, there is no negative pressure in the room, because the air conditioning unit only recirculates the air in the room.
Window air conditioners
The window air conditioner is installed directly in the window of the room. The evaporator is located inside the room and the condenser is in contact with the outside environment.
VRV (VRF) systems
VRV (VRF) air conditioning systems are designed for multiple rooms (up to 64), consisting of a separate condenser with a compressor located in the outdoor environment and several indoor units that contain evaporators. The connecting pipe leading from the outdoor unit is divided into several branches in the building in hubs (refnets) and the indoor units are connected to it. Each indoor unit is individually controlled by its own controller. The entire system can be supplemented with a central controller or a device for calculating costs (consumption).
VRV (VRF) heat pump
The system allows cooling or heating mode. The system is two-pipe.
VRV (VRF) with heat recovery
The system enables simultaneous cooling and heating mode, thus enabling energy to be pumped within the building. The system is three-pipe (possibly also 2-pipe). Indoor units are connected via BS-boxes, in which the desired mode is switched.
Impact on health
Air conditioning (with air filtering, humidity adjustment) is used in places with increased demands for a clean and hypoallergenic environment, such as operating theaters and hospital premises. In extremely hot weather, it can prevent dehydration and collapse from overheating of the body.
Improper use of air conditioning due to circulating air set to extremely low temperatures and in the wrong direction can lead to dry eyes and their burning, headaches, stiff neck muscles, dry skin, angina, exacerbation of asthma and the like. Avoiding thermal shocks during transitions between air-conditioned and outdoor environments is a fundamental measure. Neglected maintenance of air conditioning equipment, especially the replacement of filters, can lead to air pollution. The most risky is the spread of disease-causing microorganisms, especially Legionella.[1][2]