The design of an industrial cooling tower has a significant impact on the performance of the tower. To ensure optimum performance, it's important for industrial plant owners to choose the best cooling tower design in line with the requirements of the plant.
This article discusses the classification of cooling towers using different parameters. This information should come in handy when choosing the most suitable tower design.
Package Type And Field-Erected Cooling Towers
When cooling towers are classified according to the manner in which they're built, this classification gives rise to the above-mentioned types of towers.
Package-type cooling towers are assembled away from the industrial plant and delivered on-site using transportation trucks. On the other hand, field-erected cooling towers are built from scratch within the industrial plant.
Many times, package-type towers are smaller than their field-erected counterparts and they often have a lower capacity. For this reason, package-type towers are preferred for industrial plants that have lower requirements for heat rejection (e.g. textile manufacturing plants and food processing plants). Field erected towers are preferred for industrial plants that have a greater need for heat rejection (e.g. metal fabrication plants and petroleum refineries).
Atmospheric And Natural Draft Cooling Towers
This classification of cooling towers is based on the air draft mechanism that the tower uses.
Atmospheric cooling towers are designed with large rectangular chambers and louvered walls. The louvered walls allow for the natural entry of air into the tower. Thus, the performance of an atmospheric tower is tied to the speed and the direction of wind. This makes atmospheric towers much less efficient.
Natural draft cooling towers are also referred to as hyperbolic towers. In a natural draft tower, less dense (warm) air inside the tower will rise as it's replaced by cold air that has a higher density. Cold air gets into the tower via an air inlet located at the bottom of the tower. Natural draft cooling towers can have fans incorporated into the tower design (near the bottom air inlet) so as to enhance the rate of air flow.
Cross Flow And Counter-Flow Cooling Towers
This categorization of cooling towers is based on the pattern of air flow in relation to that of water flow inside the tower.
In a cross-flow tower the direction of airflow is perpendicular to that of water flow. For this reason, dry air from the atmosphere will often get into contact with warm water inside a cross-flow tower. In a counter-flow tower, air and water within the tower flow in opposite directions. Counter-flow towers ensure that dry air from the atmosphere only gets into contact with cold water inside the tower. Therefore, counter-flow towers allow for an enhanced heat transfer process, which often makes them more efficient than cross-flow towers.