What is a Cooling Tower – Components, Construction & Applications

The advent of cooling towers began in the 19th century as soon as condensers were developed to be used for the steam engines. During the 20th century, further technological advancements in the electric power generation industry fuelled progress in constructing cooling towers within the city as free-stand erections or as big cooling ponds outside cities. Nowadays, these towers are used actively in both small and large plants by considering requirements and applications. With the ability to handle a huge volume of water, these towers enable the recycling of water for further applications. This article specifically discusses the functioning of a cooling tower, components, and its types.

What is the Cooling Tower?

Cooling towers are specialized heat exchanging towers which aid in reducing the temperature of circulating hot water, which gets heated up during the industrial process. 

In this process, the water stream from an industrial process is pumped into a cooling tower through a water inlet valve and meets air in a cooling tower. As soon as the heat is extracted, the water begins to evaporate in small volumes thus plummeting the water’s temperature, sending out the cooled water to continue with the industrial process. 

Components of Cooling Tower

Some of the important components are listed below.

Drift Eliminator

Located at the top of the tower, it avoids escaping of water droplets and vapors into the atmosphere. Its foremost purpose is to ensure that the tower operates effectively by maintaining the drift rate at a minimum level and minimize the occurrence of pressure drop within a tower.

Cooling Tower Nozzles

These are made using high-quality plastics that enable and support in distributing the hot water uniformly inside the tower.

Cooling Tower Fan Motor

The tower fan motor with explosion-proof prevents leaky heat exchangers. It offers features like an overload relay system and an earth fault relay protection system.

Cooling Tower Fill

This type of tower uses efficient fill media that enables to have much more surface area to expand hot water and allow quick cooling. Two types of cooling tower fill include splash fill and film fill.

Cold Water Basin

It is manufactured using RCC. It collects and stores cold water at the bottommost part or basin of the cooling tower.

Cooling Tower Mesh

The mesh prevents the inflow of unwanted particles from the atmosphere into the cooling water.

Bleed Valve and Float Valve

These valves offer long life with less maintenance. Bled valve aids to maintain the concentration of minerals, while the float valve in upholding the level of salt and level.

Cooling Tower Air Inlet

Air inlet valves inhibit entry of sunlight at the basin, which prevents algae growth and decreases chemical cost with appropriate maintenance.

Cooling Tower Structure/Body

Modern towers are manufactured using FRP (fiber reinforced plastic) or RCC with regards to the type of application that the tower should process

The designing & classification of these towers can be done based on build, airflow generation methods, and heat transfer methods.

Construction

This tower differs in size from roof-top units to large hyperboloid structures. Based on the type of application, the structure can be up to 200 meters tall and 100 meters in diameter, while rectangular structures can be over 40 meters tall and 80 meters in diameter.

The hyperboloid cooling towers are typically used in nuclear power plants, coal-fired plants, food-processing industry, petrochemical, and other industrial plants. Hyperboloid structures are used in large plants because of superior strength, resistance to external forces and less usage of materials.

For example, the hyperboloid structure in petroleum refineries possesses the capability to circulate about 80,000 cubic meters of water per hour.

The shape of the hyperboloid offers a wide base to fit both the water and the cooling system. A unique narrowing effect of the tower helps in the streamlined flow of evaporated water as it rises and pushes towards the wide opening at the top, where heated air contacts the atmospheric air. 

Working Principle of Cooling Tower

There are various types of cooling towers developed to meet diverse industrial needs. The common working principle employed by most of the towers is “evaporative cooling”.

Evaporative cooling is described as a process in which warm water from the industrial process is pumped into the tower until it reaches the distribution system. This tower nozzles distribute this water to the wet chamber and simultaneously draws the dry air to process heated water. The water gradually loses its temperature and water droplets are collected at the basin at the base of the tower. However, the lighter droplets that strive to move upwards into the atmosphere is prevented by an eliminator provided at the top. This type of process is utilized in the natural draught fan cooling tower. Some of the towers employ forced and induced draught Fan. In this type, the fan is placed outside the tower and at the top to circulate the atmospheric air from top to bottom.

Advantages and Disadvantages

The advantages and disadvantages of the cooling tower include the following.

Advantages

• High cooling efficiency
• Needs less maintenance
• Reliability and sustainability
• Can be operated for a longer time

Disadvantages

• Possibility of scale and corrosion at the base and body of cooling towers

Applications

The applications of the cooling tower include the following.

Traditional HVAC cooling systems are used in hospitals, malls, schools, and office buildings. Much larger towers are used to reduce the temperature of circulating water in oil refineries, petrochemical plants, natural gas processing plants, and other major industrial plants to process huge volumes of heated water.

FAQs

1). Differentiate between natural draught fan and forced and induced draught fan

In natural draught – Airflow is natural and based on exit and inlet conditions of the air. No power required other than pumping water to the tank

In forced draught – Air is blown through a fan located at the top of a tower in the air inlet. Additional power is required to operate the fan.

2). List the applications of cooling tower

Traditional HVAC systems are used in schools, hospitals, offices, etc.

Large towers are used in industries like petrochemical, steel, nuclear plants, etc.

3). What is the use of drift eliminator in the cooling tower?

The drift eliminator controls the loss of water by capturing droplets and mist and prevents from entering into the atmosphere.

4). Give some advantages of using hyperboloid structure in cooling towers

The unique hyperboloid structures are often used for constructing tall towers as it provides –

• Superior strength
• Resistance to external forces
• Accelerates the upward movement of air
• Ample space and wide base

5). Cooling towers can be constructed using either FRP (fiber reinforced plastic) or RCC. Which one do you think is apt and why?

Compared to FRP and RCC, FRP is preferred as it offers significance through life cost savings, lightweight materials, have longer service lives, lower replacement frequency, high durability in corrosive environments and require little maintenance.

RCC consumes time to attain full strength, heavier to transport, needs skilled labor and consumes time to complete the construction of the cooling tower.

6). Give some applications of field erected type cooling tower.

Field erected type towers are much larger and they are used in power plants, steel processing plants, petrochemical plants, and petroleum refineries.

7). Classify the cooling tower concerning heat transfer methods

Based on heat transfer methods, the classification includes –

• Wet towers (or open circuit cooling towers)
• Closed-circuit towers (or fluid coolers)
• Dry cooling towers
• Hybrid cooling towers

8). Differentiate between crossflow and counterflow type

• In the Crossflow type, the airflow is directly perpendicular to the water flow.
• In a counterflow type, the airflow is directly opposite to the water flow.

The above article provides an overview of a Cooling Tower. The detailed classification of cooling towers is conversed along with the working principle. Besides this, we also discussed various applications, advantages, and disadvantages. Here is a question for you, what is the main function of a cooling tower?