Operation Of The Air Conditioning System
The operation of an air conditioning system installation is intended to cool and dehumidify the interior space of a home or public building. For this purpose, the vapour compression cycle is used, which consists of circulating a refrigerant material inside the system that considerably increases its temperature when it is compressed and rapidly cools down when it does the opposite, i.e. when it expands.
The exterior part of an air conditioning system is called the condensation unit and contains on one side the compressor that consumes most of the energy and the condensation coil. The interior mechanical equipment, called the air control unit, contains the evaporator coil, the interior blower and the extension or regulating valve. The controls and the ducts through which the cold air circulates complete the system.
Air Conditioning System. Vapor Compression Cycle. The steam compression cycle consists of four steps:
- The compressor (located in the outdoor unit) pressurizes a gaseous refrigerant. The refrigerant is heated during this process.
- The fans in the outdoor unit draw air through the hot pressurized gas to the condensing coil; the refrigerant gas is cooled and condensed into a liquid.
- The pressurized liquid is transported by tubes to the air control unit. It enters a regulating or expansion valve, where it expands and cools.
- Cold liquid circulates through the evaporator coils. The cooled air is filtered through the ductwork. The refrigerant, which is now a gas, is returned to the outdoor unit
Ventilation And Indoor Air Quality
Adequate conditioning of the interior environment of a house by means of an air conditioning system that cools the rooms in summer, must be accompanied by a ventilation system that guarantees the conditions of healthiness and quality of the interior air throughout the year. These systems must renew the polluted air and also reduce the excessive levels of humidity. Therefore, the construction of inefficient housing in which air is filtered should be avoided and instead the installation of hybrid or mechanical ventilation systems should be promoted, as required by the Technical Building Code. DB-HS3.
This requirement is due to the fact that in old buildings the ventilation occurs through natural ventilation and air filtration. However, these filtrations are not a controllable source of the amount of renewed air. For example, air filtration is higher during cold and windy periods, and is usually quite low during hot periods.
Mechanical ventilation systems
Mechanical ventilation systems are used to extract contaminated air from wet rooms (kitchen, bathrooms and toilets) and to supply new, clean, filtered air to dry areas: living rooms and bedrooms. These systems also allow dilution of the pollutants that are produced regularly within a house, such as moisture, CO2 produced by the metabolism of people to perform their activities, as well as other elements in suspension produced by building materials, furniture or finishes of the house.
To this aspect we must add the advantages of installing a mechanical ventilation system incorporating fans with heat recovery: this system allows to preserve the heat of the indoor environment in winter, and cool it in summer. For this purpose, the heat exchangers recover 92% of the extracted air so that the air is introduced inside the house at 66 ºF, when the temperature gradient between the outside and inside is 59 ºF. In summer the air flow is introduced at 71ºF, when the temperature outside is 86ºF and the temperature inside is 70ºF