If the design of commercial buildings is more and more linked to the performance of the building, reducing heating needs, air conditioning needs remain real. They are even more likely to be accentuated by the fact that offices are increasingly equipped with heat-generating equipment and are becoming increasingly insulated. In addition, the restrictions of use of refrigerants being ever stronger, chilled water air conditioning systems are suitable solutions to meet all these constraints.
Designed to provide air conditioning most commonly in commercial buildings and industrial buildings, chillers can be reversible and provide heating. The operating temperature of a comfort chilled water production is 7°C / 12°C. In these systems, it is water that is used as an intermediate fluid for the transfer of energy, either pure or with added glycol, unlike direct expansion systems that directly use the refrigerant as heat transfer fluid to evacuate the calories to the outside and transmit the frigories to the air-conditioning terminal units.
In the air / water systems, calories are taken from the outside air, a source of free and inexhaustible energy: the energy returned by the refrigerating machine is transferred to the water, to the transmitters that cool the rooms that require it. In water / water systems, the source of calories is water, either from the aquifer or via a cooling tower. The refrigerating machine gives its energy to a network of chilled water conveyed to the transmitters.
Water condensation has a greater thermal capacity than air condensation and a better EER (Energy Efficiency Ratio), especially since this solution is less dependent on outdoor temperature conditions.
Other systems exist, such as water loop air-to-water heat pumps, which had boomed in the 1990s and then declined in sales. They are now making a comeback as noticed by some manufacturers because they have advantages in terms of installation: can be installed as lighter systems, and can ensure the renewal of fresh air and the extraction of stale air through the outer walls. The air intakes are thus invisible, directly integrated in the facades. A major asset for renovation projects, chillers requiring the passage of pipes of larger diameter than the direct expansion systems and indeed more difficult to implement in the existing structure. As equipment evolutions tend towards ever more energy performance, the chillers currently on the market operate for the most part with Inverter compressors in order to adapt the speed according to demand, by varying the frequency of the current. In addition, more and more distribution systems in service industry buildings are implementing variable speed auxiliaries, such as circulation pumps.
Another systems using chilled or hot water to provide cooling and / or heating functions are the fan coil units. Installed in the rooms to be treated, they consist of a cold battery, a filter, electrical resistances and a fan. In the "2-pipe / 2-wire" version, the two tubes correspond to the return flow of the chilled water for the cooling operation. The two wires correspond to the power supply of the resistors for the heating operation. The fan-convectors allow an individualisation of the comfort, the heating and cooling modes functioning independently in the various premises to be treated. Here too, performance is sought: more and more equipment is equipped with low consumption fans.
Water systems are the subject of two European Eurovent certification programmes. Among the characteristics certified by the program "Chillers (LCP-HP)": cooling capacity, electrical power absorbed, energy efficiency coefficient, heating power, coefficient of performance, pressure drop of the liquid, available pressure, pressure drop at the condenser ...
As for the program "Fan Coils (FCU)", it concerns all fan coil units, sheathed and unsheathed, variable speed or not, and certifies three sets of characteristics: thermal, acoustic and aeraulic.