Cooling Tower | Types | Working Principle

Types of cooling tower:- Utilities are neither a reactant or nor a catalyst still its absence can impact the chemical reaction. Utilities are equivalent to the heart of any industrial process as they play an important role in maintaining adequate requirements of a product process.

There are different types of utilities used in the chemical industry, among those we are talking about the basic utility i.e. cooling water. Wide use of cooling water can be see in manufacturing industries such as in reactor jacket, in heat exchangers, in jackets of furnaces, and many more.

Previously we had posted detailed tutorial on Cooling Tower efficiency calculation and Cooling Tower Approach so do read if you are interested in it.

Cooling water is a utility that is used as both cold side and hot side fluid in heat exchangers depending on the temperature requirement. The general flow of the cooling water in an industry is described below steps.

1. Cooling water is pumped from the reservoir to the plant where it is used in the reactor’s jacket, in heat exchangers, in the jacket of the furnace.
2. After exchanging heat from those equipment, its temperature got increased hence it is sent to cooling tower.
3. Cooling towers reduce the temperature of the water.
4. The water again pumped to the plant and use as a utility for plant.

This is the basic flow of cooling water, where cooling water is taken from the reservoir and pumped to the plant and after that, the temperature is reduced by the cooling tower and again it is pumped to the plant. Hence to use the water again, the cooling tower is used. In this article, we will learn the types of cooling tower, the working principle of cooling tower, and how cooling tower works.

What is a cooling Tower?

The industrial cooling tower is a device that acts as heat rejection equipment. It rejects waste heat from the water and thereby reduces the temperature of the water. It is used in industries to reduce the temperature of water and thereby provide cooling water utility for the process.

Working principle of cooling tower – How does a cooling tower work?

Cooling tower works on the principle of evaporation. Hot water is sprayed from the top of the cooling tower which exchanges heat with the atmospheric air and results in a reduction of the temperature of hot water.

The convection mode of heat transfer is used in the cooling tower are heat transfer takes place between air and water.

Types of cooling tower

There are different types of industrial cooling tower. Classification of industrial cooling tower is described below

Natural Draft Cooling Tower

A natural draft cooling tower works on natural convection to circulate the air completely through the tower.

• Hot water that comes from the plant and is to be cooled pumped using a pump to the top of the cooling tower which is considered as inlet of the cooling tower or hot water inlet.

• The hot water inlet is connected to a series of nozzles also known as distributor with the help of which it gets sprayed over the fill material evenly. The purpose of filling material is to provide a more contact surface area for heat transfer.
• Fresh air is induced at the bottom of the tower which then flows in the upward direction where heat transfer takes place between warm water coming from the top and and cool air coming from the lower side.
• The hot water rejects heat after contact with air and in that process fraction of the water gets evaporated.
• Water getting cooled after heat transfer is collected at the basin or the bottom of the tower and hot/Warm and moist air gets discharged from the top of the tower to the atmosphere.
• Air movement takes place because of the difference in density between the air that enters inside and the one that is already inside the tower. The warm and moist air is lighter as compared to the cool air and therefore, it rises through the tower. The dry and cool air from outside the tower will fall in, creating a constant cycle of airflow.

In this way, the Natural cooling tower works.

Different types of chemicals are dosed in the cooling tower for water treatment and those are discussed in Chemicals used in cooling tower water treatment article.

Mechanical draft

The working principle of a mechanical cooling tower is pretty much the same as a natural cooling tower which is the principle of evaporation but the only difference is here the air is circulated through mechanical means. Here fans/ propellers are used to create air.

Mechanical draft cooling towers are again of two types:

1. Forced draft cooling tower
2. Induced draft cooling tower

1. Forced draft cooling tower

In the Forced draft system, an exhaust fan placed at the base which forced the air to flow from the bottom to top of the tower. A drift eliminator is installed inside the tower to prevent the loss of water droplets along with the forced air.

2. Induced draft cooling tower

In an induced draft cooling tower. the fan is installed centrally at the top, which creates suction in the cooling tower and discharges it to the atmosphere. This creates a flow of air from bottom to top with a force and results in a reduction in the temperature of hot water. The only between the induced draft and forced draft is that the fan is located at the top in the induced draft.

This was the classification of mechanical draft industrial cooling tower based on the placement of fans.

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Types of industrial cooling tower based on airflow pattern

Other types of are categorized based on airflow patterns. There are two type

1. Cross-flow cooling towers
2. Counter flow cooling tower

1. Cross flow

In a crossflow cooling tower, hot water sprayed from the top which is perpendicular to air which enters from the sidewalls of the tower horizontally and then rises upward from the center of the cooling tower. In crossflow air enters at 90 degrees in the direction of the water. As the flow of water and air cross each other, these types are called crossflow cooling towers.

2. Counter flow

In counterflow cooling towers, The water is sprayed through the pressure nozzles near the top of the tower and flows down through the fill material and air enters beneath fills and moves upward opposite to the direction of the water flow. As the airflow and water flow in the cooling tower are in counter to each other, theseare called as counter-flow cooling towers.

FAQ (Types of cooling tower0

Wrapping Up

Hope you like this tutorial on cooling where we had tried to cover all the aspects about cooling tower along with calculation. In the meantime, you can detailed post on Vapour absorption Chiller (VAM) which is used in the chemical industry to create chilling water. read If you find this information useful then do please us in the comment section.