The process of cooling can be defined as thermal energy transfer from one medium to another medium. Cooling is a very critical requirement in various industrial applications, in order to ensure that any process may not cause the product or equipment to overheat.
Water is used in many cooling applications as a medium for absorbing heat, as water has a high boiling point as well as specific heat.
Cooling water treatment can be done in many different ways but the 3 basic types are presented in this article to show how cooling water can be used in each of the systems.
Once-through cooling system
Here in this cooling system, from the certain nearby water source, water will be pumped and will pass through the system only once for absorbing the process heat.
Thereafter it is discharged back into its original source from where water was drawn like well, river, lake or even ocean.
This is a very common design where low-cost water of large volumes is available. Besides that, such systems are used for the following conditions:
- When demand for cooling is usually from low to moderate
- When the processes are not very critical
- When there is sufficient room available to accommodate large-sized equipment and also a high quantity of water.
The drawback of this once-through cooling system is susceptibility to various disturbance by different stochastic water events like flooding.
Besides that, these systems are nowadays phased out because of concerns about the quality of water and their conservation.
Closed recirculating system
This kind of closed recirculating systems is also known as dry cooling towers, where the heat absorbed by cooling water will either be transferred to any second coolant, or it will be released into the open atmosphere.
This is also called a dry cooling tower because the water will never be exposed to open air in the atmosphere, and because of this only very little amount of water will be lost.
A very good example of such a closed cooling system can be an automobile engine. Here evaporation will not be used and instead, cool air will rush over a few series of smaller tubes that contains circulating coolant.
Here heat will be transferred from all the hot liquid that is inside tubes to cool air, which will result in cooling. Finally, the coolant will be returned back into the engine.
Open recirculating system
This kind of open recirculating type of cooling systems is also known as wet cooling towers or evaporative cooling tower and these are very widely used types of designs in the industry.
We saw in the above closed recirculating system the same water of the open system is used here over and over.
The most visible feature of this system is the very big outdoor cooling tower which uses evaporation for releasing heat from cooling water.
Because of this mechanism only, this kind of cooling tower has also been given the name of the evaporative cooling tower.
There are is 3 main equipment in this kind of system which as follows:
- Recirculating water pump(s),
- A heat exchanger(s)
- The cooling towers.
Information Source: https://sensorex.com/blog/2018/02/21/how-cooling-towers-work/