A free cooler system can be employed to cool several types of fluids, such as water, glycol water, hydraulic oils and diathermic oils. But in order to use a free cooler the maximum inlet temperature of the fluid must be up to 99° C and the freezing point at least 5 K degrees under the minimum temperature reached during winter within the installation area.
In case of operations with water, at last, free coolers don’t involve any water consumption neither vapor emission, no limescale deposition and no bacteria contaminations, thanks to the fact that the water circuit is not in direct contact with air. The water employed remains always the same, and its quantity is easily monitored, avoiding the need to undergo severe disposal regulations or waste water treatment processes.
The selection of a free cooler system, or otherwise of another kind of cooling system, must therefore be considered thinking about the thermal duty that has to be dissipated, and also to the cold levels that must be reached in a specific process.
Aiming to reach temperatures lower than 25° C, a chiller is the most suitable solution.
Aiming to reach temperatures higher than 25° C, but under 35° C, evaporative towers are the best choice.
For temperatures higher than 35° C, free coolers or dry coolers become a good option.
Environmental evaluations being done – ambient air temperature and humidity rate – for options # 2 and 3, a free cooling solution could then be the most simple to manage and advantageous in all of those applications requiring water at a temperature higher than ambient air temperature, throughout all – or almost all – of the year. To bring some example, water at a temperature of 40° C is ‘cool’ enough for oil cooling in hydraulic presses, or also for the cooling water employed in quenching baths in metals’ heat treatments. In all of these cases, a free cooler can easily be employed throughout the whole year. If the required temperature is instead lower than ambient air temperature, or anyway lower than wet bulb temperature, the use of a chiller becomes mandatory, which allows to reach low temperatures even very much under zero degrees.