In case of average cooling temperatures, the integrated free cooling can then be a very interesting solution. This solution allows to use the free cooling system during the colder months of the year, achieving high energy savings, while switching back to the chiller during the warmer months. During the mid-season, it will be possible to use them both in combination. Combining a free cooling system as integration to a chiller can unfold very interesting opportunities in terms of management savings, drastically reducing the costs of the overall cooling system.
The installation in series of a free cooling and a chiller leads the this functioning cycle: when the temperature of the fluid to be cooled coming from the production process is lower than the ambient air temperature, an automated bypass system – composed by a switching valve and a temperature sensor – will keep out the dry cooler from the circuit. This avoids water at a lower temperature than ambient air to flow within it. Otherwise, whenever the temperature of the incoming fluid to be cooled is higher than the ambient air temperature, the free cooler is not excluded, because the flowing within it of the fluid will provide a first cooling contribution to the overall cooling process, which will then be completed by the chiller.
A free cooling + chiller combined system, instead of a unique refrigerating machine, brings its benefits when the free cooler can provide a contribution to the cooling process – a total cooling task or even a partial cooling contribution – throughout the whole year. In this case is it indeed possible to under-size the chiller compared to the maximum cooling capacity required, with a lower cost of the plant and an advantage that must be evaluated every time based on the amount of the free cooling-mode contribution. In fact, is it possible to make a comparison between the costs of a chiller, a closed-circuit water refrigerator, and a free cooler, an air finned-pack water cooler: being equal the amount of dissipated thermal load, the cost of a free cooler is lower by 20% compared to a chiller, and its power consumption equals the amount of 10% of the energy consumed by a chiller. And the energy saving increases as the capacity of the plant grows.
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