Here is an example of systems of differentiation for water cooling at low temperature required for realizing specific production processes: cooling plastic material molds, air conditioning, etc.
In some plants, cooling towers are not recommended for cooling machines. This is because these machines require low temperatures. In any case, it’s not about disposing waste heat, but the need to use cold temperature for specific tasks.
A molding plastic materials machine has two different consumption that need to be cooled in the same machine.
A first consumption is made from the mold that needs to be cooled with water at low temperatures (+ 5-6 °C), in order to allow for fast production.
The molding of plastic materials requires:
a preheated mold,
the injection of the molten plastic to be shaped by the mold, and
fast cooling allowing the detachment of the molded piece from the mold itself.
The whole procedure is very efficient if the time is limited. This is because it allows for a high cadence of production.
In the same plastic molding machine there is installed a hydraulic power unit. This component allows the services to activate the machine itself.
The diathermic fluid needs to dispose of the heat through the water/oil exchanger. Normally this is done through a shell and tube heat exchanger.
So, these two consumptions require a different water temperature.
In the case of the mold, the required temperature is about 6-8 °C.
In the second case, with the cooling tower, it’s possible to cool down up to 40-45 °C. But, it’s not possible to cool down to 6-8 °C.