The field of indirect free-cooling systems is a free cooling chiller. When the equipment operates as a compressor, the cooling of the liquid in the consumer circuit occurs in the evaporator. However, in the off-season and in winter, you can cool the room by taking air from the street. This requires an addition in the form of a circuit equipped with a dry cooler. In systems using free cooling air cooled chillers, there are three main types.
Free Cooling with Closed-circuit Cooling Towers
In a closed-loop free cooling system, the return cooling water is pre-cooled before it enters the evaporator. This reduces the load on the chiller and increases the efficiency of the entire system during intermediate seasons.
- In cooling towers, depending on the design, the water can be cooled to a temperature 3-6 ° C higher than the wet-bulb temperature.
- In closed-circuit cooling towers, the water temperature is provided at a level of 2-3 ° C above the temperature that can be reached in open circuit cooling towers.
- Ideally, the water temperature can be achieved near wet-bulb temperature by increasing the size of the cooling tower, however, this increases the capital cost significantly.
Although the use of cooling towers is attractive in terms of capital costs, they can cause operational problems. This is because the water from the cooling towers is directly fed into the cooling system, which in turn can cause fouling and limescale deposits on the surfaces of the heat exchangers. Moreover, that part of the water that evaporates in the cooling towers must be constantly replenished.
Finally, the water must be periodically cleaned or replaced in order to avoid sedimentation in the cooling tower vessel. When deciding on the use of this system, it is necessary to take into account the problems associated with water loss and pollution.