Forced Draft Cooling Tower: Overview, Parts, Working, Advantages, And Applications

Most of the power plant comprises four essential components. They are boiler, condenser, pump, and turbine. 

The condenser is a heat exchanger that condenses the exhaust steam from the turbine into liquid form at a similar temperature and pressure. 

Steam that passes into the condenser exchanges heat with the cold water from the cooling tower. So at the end of the heat exchange process in the condenser, the hot water is released from the outlet valve. 

This hot water will be sent to the cooling tower to cool down. This cooling water will again move toward the condenser for the heat-exchanging process. 

So, the cooling tower plays a significant role in power plants. It is an open heat exchanger device that helps cool the hot liquid from the condenser by exchanging the heat with the atmospheric air. 

The forced draft cooling tower is a cooling tower in which a fan is located at the base of the tower. The fan helps to move the atmospheric air inside the cooling tower. 

The performance and heat transfer are much better in forced draft cooling towers compared to other cooling towers. These cooling towers are used in various industries like power plants, petrol chemical and refining industries, and many more.

The article discusses more about forced draft cooling towers. So you can keep on scrolling through this article to know forced draft cooling towers, their advantages, and applications.

Types Of Cooling Tower

There are mainly two types of cooling towers, i.e., natural cooling towers and mechanical cooling towers. 

1. Natural Draft Cooling Tower

The fresh air directly enters the cooling tower. There is no use of a fan in the natural draft cooling tower.

The heat exchange occurs between the hot liquid from the condenser and atmospheric air. The air extract heat moves upward and goes out of the cooling tower. 

2. Mechanical Draft Cooling Tower

Mechanical cooling towers use single or multiple fans and force the atmospheric air inside the cooling tower. 

These towers are reliable and stable in comparison to natural cooling towers. It is because the airflow can be adjusted according to the variation in cooling load. The mechanical cooling tower is divided into forced and induced draft cooling towers.

• Forced Draft Cooling Tower

The fan is located at the tower’s base, which forces the atmospheric air inside the cooling tower. The velocity of atmospheric air at the inlet is relatively high as it is drawn inside by the blower. 

But its velocity gradually decreases as it upwards in the tower. So, there is the possibility of recirculation of air in the forced draft cooling tower. 

• Induced Draft Cooling Tower

The fan is located at the top of the cooling tower, drawing air from the tower’s bottom or sides. In this arrangement, the air will have less velocity at the entry but higher velocity at the exit, which is the opposite of the forced draft cooling tower.

Parts Of Forced Draft Cooling Tower

There are various components of the forced draft cooling tower. We are listing them below.

1. Fan Or Blower

The fan or blower is usually located at the base of the cooling tower and can be centrifugal or axial. The main work of the fan is to force air inside the cooling tower. 

2. Cold Water Basin

The water basin is located at the bottom of the cooling tower. It stores the cold water inside the condenser tubes by the primary cooling water pump. 

This cold water will exchange heat with the turbine’s exhaust steam and become hot. This hot liquid will again go back to the forced draft cooling tower.

3. Tower Support

There is tower support between the tower and the cold water basin. The base of the tower support is approximately 10-15 feet away from the cold water basin. Circular pillars support the base of the tower.

4. Fills

Fills are an essential component in a cooling tower. It is made from plastic or any other material with a high heat transfer coefficient. The primary purpose of fills is to provide a large surface area so there will be proper heat exchange between the air and water.

5. Header

The hot liquid from the condenser moves inside the cooling tower through the header. There are spray nozzles located just below the header. Its work is to spray the hot water in the form of mist.

6. Hot Water Distribution Pipe:

The hot water distribution pipe is used to supply the hot water to the forced draft cooling tower. From this pipe, the hot water reaches the spray .nozzles.

7. Spray Nozzles

The water from the hot water distribution pipe reaches the spray nozzles. The spray nozzles spray the hot water n the form of mist and this spray is directed towards the fills.

8. Drift Eliminator

The drift eliminator captures the water particles from the air, which go out from the cooling tower. Hence it prevents water droplets from releasing into the atmosphere.

Working Of Forced Draft Cooling Tower

The hot liquid from the condenser enters the cooling tower through the header. The spray nozzles present at the base of the header spray it in the form of mist. In the meantime, the fan at the tower’s base forces the air inside the cooling tower. 

The heat exchange between the air and the hot water occurs in the fills. The fills have a maze-like structure, which helps increase the contact between the air and hot water, and thus there will be better heat transfer. 

The hot liquid from the condenser is at a high temperature compared to the air entering the cooling tower. As a result, the hot liquid rejects heat to the air and finally cools down. It is further collected in the water basin present at the bottom of the cooling water.

The hot air moves upward and passes into the drift eliminator. During the heat exchange process, some water droplets mix in the air. The work of the drift eliminator is to remove these water droplets from the hot air. So, after passing through the drift eliminators, the hot air finally escapes from the cooling water.

Advantages Of Forced Draft Cooling Tower

1. Good Performance

The fan is at the base of the cooling tower, which ensures a steady flow of air inside the cooling tower and yields better performance.

2. Remove heat

A forced draft cooling tower helps to remove the heat generated in the production process.

3. No Blade Erosion

The fan is present at the side of the forced draft cooling tower. It handles only dry air, so fan blades will not be corroded.

But if we talk about the induced draft cooling tower, the fan is at the top of the tower.

The work of this fan is to pull air from the bottom to the top. But the air at the top may contain a few water particles, which can damage the fan blades.

4. Safe

The fan is present on the ground level. So it is more safe in compared to the induced draft cooling tower.

5. Vibration And Noise 

The vibrations and noise are less in the forced draft cooling tower as all the mechanical components are at ground level.

Disadvantages Of Forced Draft Cooling Tower

1. Recirculation

Recirculating hot exhaust air from the top of the tower is possible.

2. Fan Size

You cannot exceed the size of the fan. Its size is only limited to 4 meters.

3. Ice Formation

Ice can form on the fan blades in cold weather.

Applications Of Forced Draft Cooling Tower

• Power plants
• Petrochneical industries
• Paper industry
• Manufacturing industry
• Steel and metal industry
• HVAC industries

Conclusion

A forced draft cooling tower is essential in power plants and several industries. It is more efficient in comparison to an induced draft cooling tower. But recirculation can be an issue in certain weather conditions.

We have discussed above forced draft cooling tower in detail. If you have any queries, you can ask us in the comment section.