Cooling Tower Definition

Candela Rocío Barbisan
Chemical engineer

A cooling/refrigeration tower is a type of direct heat exchanger in which the fluids exchanging energy are in full contact with each other. In general, they are designed to cool water, extracting energy in the form of heat by the evaporation of the water, forming steam, therefore, in a cooling tower there is a transfer of heat and mass. That is to say, heat transfer occurs by convective mechanism and steam transfer from the water to the air (which leaves the tower with a high percentage of humidity). There, a service current widely used in the industry is produced, which is “tower water”.

parties

A cooling tower is a very always equipment in terms of its components and its design. It consists of a casing that surrounds the filling or the evaporators, through which the water will circulate. Likewise, there are one or more fans, they can even become blades depending on the size and cooling requirements. These fans are driven by a motor. In general, the flow inside the tower is counter-current flow, this implies that the water enters through the upper part, is distributed and comes into contact with the air, which enters from below, inducing its circulation through the fans located in the upper or lower part, depending on the type of tower.

When the water enters, it does so through a distribution system with sprinklers, in order to efficiently distribute the fluid inside. For this, there are open channels (generally GRP) or dispersing plates, which ensure uniform distribution of the fluid within the fill. The water can come from a tank or from a closed circuit, having been previously used in a process and redirected, after passing through the tower, to another piece of equipment.

When water falls, it does so through a filler, which allows the contact area to be expanded and heat transfer to be improved. Therefore, there are many types of fillers, depending on the type of water to be treated. In general, it is recommended: laminar filling if the service is clean or water for industrial use; mixed fill if the water may contain traces of solids and splash fill when working with a service with high probabilities of clogging, solids in suspension, content of oils, fats, paraffins and/or fibers. The padding material can range from wood to PVC.

The separators of drops in general are also formed by sheets of PVC or PP, which minimizes the losses of water by dragging. Drop separators are also known as dew eliminators, a name that derives from their function.

Types of tower depending on the shot

There are three types of towers: natural draft, induced draft, forced draft or crossflow cooling tower. As its name indicates, each case is easily identifiable.

In the first case, it is said that the tower has natural draft when it does not have fans or blades, since, due to the simple difference of air density, moist air leaving the tower and absorbing moisture from the water is more dense than cooler air, air atmosphere. This is the case of the towers of thermal power plants, where the sizes to achieve the desired cooling are high and require high water flows.

When the cooling tower is induced draft, a fan is placed at the top, which induces the air current to flow from the bottom, through the filling, coming into contact with the water and leaving as saturated air at the bottom superior. It is the typical tower model for being considered the most efficient in terms of design.

Forced draft towers locate the fan at the bottom. The air works against the current, since the fan induces its exit through the upper part. The water, as in the case of induced draught, enters at the top through the distributors and falls towards the bottom, where it is collected.

Lastly, cross flow towers work with perpendicular flow between streams. The water enters through the top and is collected at the bottom of the tower, while the air enters horizontally and crosses the water perpendicularly.