A cooling tower is a unique heat exchanger that lowers the temperature of water through the cooling effect of evaporation. It works by bringing water and air in direct contact with one another, after which a portion of the water gets evaporated, thereby lowering the temperature of the water passing through the tower.
In industries, machines tend to absorb heat over time, and without a cooling tower, this may lead to overheating and eventually, faulty machines. Several types of industries make use of cooling towers including refineries, natural gas, and food processing industries.
It is important to note that cooling tower maintenance is of paramount importance to the successful operations of these industries. However, to conduct proper maintenance, it is crucial to understand what makes up cooling towers and how they operate.
Cooling Tower Components
The parts that make up a cooling tower include:
- Gearbox
- Motor
- Fans
- Driveshafts
- Fill Media
- Drift Reducers
- Nozzles
- Air inlet louvers
- Electronic valves
- Reservoir heaters
- Float valve
- Distribution basin
- Piping
How Cooling Towers Work
The cooling tower’s mode of operation depends on the type of cooling system it uses. That said, there are 3 basic types of industrial water cooling systems, namely: once-through cooling system, closed-recirculating system, and open recirculating system.
Once-through Cooling System
A once-through cooling system involves the siphoning of water from nearby water sources and passing it through the system to lower its temperature. The water may be from groundwater sources like wells, rivers, lakes, or even oceans. After the water passes through the system and absorbs the heat, it is then released back to its original source.
Although this design is low-cost, it is not commonly used due to water quality concerns. Furthermore, it is very effective only when the cooling demand is at a medium. An example of this system can be seen in potable water systems.
Closed-recirculating Water system
Here, water is passed through the system to absorb heat, after which it is transferred to a secondary coolant or released to the atmosphere. This system is also called a dry cooling tower because, even though air comes in contact with it, the water does not get exposed to air at any point. Instead, air comes in via several small tubes that possess their own coolants. The heat absorbed by the water is transferred to these tubes, then cooling occurs.
As a result of this enclosed system, very little water is lost. An example of this system can be seen in car engine radiators.
Open-recirculating Cooling System
The open-recirculating water system, also known as wet cooling towers, is the most widely used in industries due to its effectiveness and versatility. Its effectiveness is a result of three main parts working together- the recirculating water pump, heat exchanger, and the cooling tower.
Cooling water from the system’s wet towers is positioned to come in contact with an upward airflow. Furthermore, the heat exchanger ejects water above the top of the cooling tower which drops and scatters as it passes through the splash plates of the cooling tower fill. As the water hits the cooling tower fill, the hottest molecules evaporate from the tower. The remaining cooled water is collected at the distribution basin and pumped back into the heat exchanger as the process repeats itself.
