Large commercial and industrial production units generate a lot of waste heat. Retention of such heat drastically affects the functioning of the entire system. As such, there need to eliminate the waste heat quickly.
A cooling tower can remove this excess waste heat by lowering the temperature. Ideally, this heat rejection device utilizes an evaporative heat process to channel the heat to the atmosphere.
Depending on the different plant needs, there are different cooling tower types available. And a clear idea about how they work is valuable to choose the right cooling system for your production.
How do cooling towers work?
Cooling towers are a heat exchanger that cools a stream of water. This is done by allowing water to come in contact with air causing heat loss from warm water.
Warm water (waste heat) entering the tower is pumped to the water distribution system, i.e., tower nozzles, which distribute water onto a “fill media.” The fill media does two things:
First, slow the speed of water flow.
Second, it maximally exposes water to the air for the best water-air contact. This contact causes the evaporation of water. Remember, the large fans constantly draw in large volumes of air.
When water comes into contact with air, small portions of water evaporate, carrying heat causing cooling. The evaporating water moves towards the top of the tower and is expelled into the atmosphere.
The remaining water – cold water, re-circulates via the heat source, and the cycle repeats repeatedly.
Cooling Towers Type
There are different ways to classify cooling towers. However, three standard classifications are widely recognized. They include:
This is the broadest classification of cooling towers. Under this category are two types of cooling towers
- Field-erected products (FEP)
Field-erected cooling towers are suitable for heavy commercial and industrial plants, i.e., higher heat rejection and high-volume water requirement. Since they are large-sized, their construction commonly occurs at their site of use.
- Factory-assembled products (FAP).
These tower types are ideal for light industrial markets, where they serve as HVAC. Since they are considerably smaller than the field-erected types, they are assembled at the factory before being shipped for installation at the site of use.
Mechanical and Draft Type
This classification covers how air enters the tower. Three types exist:
- Natural draft (FEP only)
The density differential between heated air within the stack and ambient air outside the tower produces the natural air flower. This is common in heavy commercial and industrial applications.
- Induced draft
These towers feature axial fans at the air discharge point—the fans aid in pulling air into the towers. Induced draft towers are the most popular options. You can find them in HVAC markets, power, and industrial applications.
- Forced draft
These towers use centrifugal fans at the air inlet. Their primary advantage is that they can operate against high static pressure, common in ducting. Additionally, you can install it indoors. But do remember they can be expensive as they consume a lot of power.
Air/water Flow Generation
Air-water contact addresses the method by which water and air come into contact. There are two methods – Crossflow and Counterflow. Both are finding wide application in FEP and FAP cooling towers.
- Crossflow cooling towers
Air flows horizontally across the direction of the falling water. Ideally, water flowers downwards through the fill media as air flows through it.
Moreover, this tower requires minimal maintenance and better tolerance to cold water. However, it’s expensive.
- Counterflow tower
Air travels in the opposite direction to the direction of the falling water. Air moves vertically while nozzles at the top of the tower spray water, flowing downwards through the fill. Their most significant advantage lower pumping cost, making them a popular tower type.
These towers are physically smaller than the crossflow towers of a similar capacity, making them a better choice for smaller spaces.
So, what are the standard options in the market?
While there are many classifications, you are bound to choose between these two main types of cooling towers.
Choosing the right cooling tower type depends on the material and system operations. Remember, material choice determines the longevity of the tower since they are in direct contact with water. The right material alongside water treatment keeps the tower safe.
Diverse factors affect system operations. Common ones include warm water temperature, air pressure drop, dry-and wet-bulb air temperature, and the air-water contact efficiency.
The stability of the entire structure is essential. Cooling towers are prone to damage, especially from the wind. Therefore, while building, it is essential to offer enough structural support to the whole system and regular maintenance to maximize the efficiency of the cooling tower.