Cooling towers are mainly heat-extracting devices that efficiently remove excess heat from the industrial process and transfer it to the atmosphere. Based on working principles, they can be evaporative or dry/wet cooling towers.
This blog post will explore the different types of cooling towers, from wet to dry, crossflow to counterflow, and induced draft cooling towers to forced and natural cooling towers, as well as their working methodology, specifications, and advantages.
Why Cooling Towers are Essential in Industries?
Effective cooling solutions in any manufacturing unit are as essential as the production process, which maintains optimal temperatures, prevents overheating, and promotes overall plant efficiency. As different parts of the plant operate, they produce heat that steadily builds up, impacting system functionality, productivity, and overall operational stability.
Cooling towers provide industries with a cost-effective solution to manage heat, reduce equipment damage, and enhance productivity. Instead of other costly methods, cooling towers have an economical way to optimise energy consumption, extend equipment lifespan, and minimise downtime, resulting in significant cost savings.
Natural Draft Cooling Towers
Passive draft cooling towers or natural draft cooling towers use natural convection, and cooling tower fans are not used. Warm and moist air naturally rises through the cooling tower, and due to air density differences, a specific movement pattern is created.
The dry and cold air entering the cooling tower is less dense than the hot and moist air removed after hot water contact. As a result, due to light eight, warm air rises, and cold air falls. The main principle working behind this natural draft is the chimney effect and air density differences.
Now, a constant pattern of air circulation has been established that assists in cooling down the incoming hot water and exchanging heat for better efficiency.
One of the most influential and particular natural draft cooling towers is the “Hyperbolic Cooling Tower”. It is based on the chimney-stacking design that pushes the hot air outside the cooling towers.
Natural draft towers are not expensive as they do not use mechanical equipment like fans or fan motors. This process is considered energy-efficient, too.
On the other hand, the space requirements are typically higher than the other types of cooling towers, and environmental and climate conditions also have to be considered while installing a natural draft cooling tower. They are commonly used in different industries like coal-fired power plants.
Induced Draft Cooling Towers
Unlike natural draft cooling towers, fans and other mechanical equipment are used in the induced draft cooling towers to move out the hot air through the tower. They have large fans placed at the top of the building, pulling the cool air through the cooling tower.
Working Principle of Induced Cooling Tower
The working principle of this type of cooling tower is based on establishing the negative pressure inside the cooling tower to remove the warm air through the structure.
- The process begins when the hot water from the industries is gathered at the button and distributed evenly over the fill media through the spray nozzles.
- The fill media of the cooling tower provides a larger surface area for heat exchange; the more significant the surface is, the more heat transfer occurs. Fill media acts as a heat exchanger here.
- Cold air flowing over the fill media moves over the cooling tower fills media and contacts with the hot cooling tower water, and some of the water evaporates. This evaporation process withdraws the extra heat from the water.
- The hot air from the evaporation is withdrawn from the top of the cooling tower.
- In an induced draft cooling tower, air moves at a high velocity, so there is a minimum risk of recirculation.
- Cold water is collected at the bottom of the cold water basin and can be redistributed for proper and effective cooling and transferred back into the industrial processes.
The induced draft cooling tower has adjustable cooling tower components, such as an adjustable tower fan speed mechanism, to ensure maximum working efficiency.
Forced Draft Cooling Towers
It is a common type of mechanical draft cooling tower that pushes air into the cooling tower to maximise the convection process for efficient heat exchange. Its working method is almost the same as that of the induced draft cooling tower, but the positions and placement of the fans are different.
They have cooling tower fans located at the tower’s base or sides, and the fan forces air into the tower system, hence called “Forced draft cooling towers”. These fans play an essential role in increasing the natural thermal circulation.
The forced airflow is controlled by the overall water distribution system and the tower’s fill media, where most heat exchange occurs. The low velocities of air in the forced draft cooling tower make them more vulnerable to unnecessary air recirculation.
Its unique structural design is perfect for controlled and continuous airflow but is highly costly and inefficient to proceed due to massive energy consumption.
Crossflow Cooling Towers
These types of cooling towers are designed so that the airflow is perpendicular to the water flow, thus the name crossflow. This enables optimal heat transfer, making crossflow towers suitable for various applications. Crossflow cooling towers are mainly used in various industrial processes, such as power generation, nuclear power plants, food processing, HVAC systems, and manufacturing.
The work involves a combination of air and water flow to dissipate heat. Hot water from the plant is pumped to the top of the tower, where it is distributed through nozzles, which allow for optimal heat transfer by creating a uniform curtain of water. As the water falls on the splash fill, the air enters from the louvres from the sides and flows horizontally, crossing the falling water.
The water heat is transferred to the air, and the water becomes cool. It is collected in the basins at the bottom and then recirculated.
One of the characteristic features of this tower is the use of PVC or polypropylene fill-in material, which increases the contact area between air and water. Similarly, drift eliminators are applied to minimise water loss.
Counterflow Cooling Towers
As the name shows, counterflow towers allow airflow horizontally inside the cooling tower while water flows vertically, entering from opposite sides of the cooling towers. Like crossflow cooling towers, in the counterflow, water falls from the topmost of the cooling tower.
Air also enters the cooling towers from the bottom and moves vertically upward against the water direction. That’s the main difference between counterflow and crossflow cooling towers. Because of the upward airflow, the counterflow cooling towers can’t use the gravity flow basins. Hence, powerful and pressurised spray nozzles are used to distribute the hot water smoothly on the cooling tower fill media for effective and maximum heat transfer. The heat exchange mechanism is the same as that of other cooling towers. Like the cold air moves upward and comes into contact with the falling hot water, some of the water evaporates, leaving behind less hot water, and the cooling process occurs.
Drawbacks of the Counterflow Cooling Towers
- They are more inexpensive and modest than the crossflow cooling towers, hence providing maximum efficiency within budget because of their unique cooling tower design.
- However, the main drawback of counterflow cooling towers is that larger pumps are required to force air against the hot water flows, which ultimately results in higher electricity bills and operational efficiency.
- They also produce more noise than cross-flow cooling towers.
Wet Cooling Towers
- Wet cooling towers, or evaporative cooling towers, extract extra heat from large buildings, industries, air-conditioning condensers, and commercials through water evaporation. Nowadays, numerous companies and enterprises use cooling towers to maintain their building’s temperature to function smoothly and effectively. Sometimes, they are also called open-circuit cooling towers, using natural evaporation to cool the overall machinery.
- These towers only rely on the heat exchange of the air and water. Whenever any machine part starts to heat up to gather more heat than the controlled amount, the cooling tower’s cold water travels through the labyrinth in the structure and absorbs the extra heat.
- This warm water is then dispersed over the fill media through the spray nozzles as water droplets to enhance the surface area for effective heat transfer. Some portion of hot water evaporates by absorbing a significant amount of heat, leaving cold water inside the cooling tower.
- The remaining cold water is recollected at the bottom of the tower, in the cold water distribution basins, and pumped back to the industrial process to cold heat up things again. This process is continuous, and cooing takes place uninterrupted. Dry cooling towers
Hybrid Cooling Towers
If we talk about the cooling tower’s efficiency based on the heat transfer methods, we have four types of cooling towers; such as
- Closed-circuit cooling towers: In this type of cooling tower, a hot waiter is passed through the heat exchanger of the cooling tower system, which is clean, and hot water is prayed. Its working pattern and efficiency are similar to the wet cooling towers.
- Wet cooling tower: As discussed above, it relies on the evaporation cooling principle.
- Dry cooling tower: They worked in the same pattern as the air-cooled chillers, air conditioning systems, or automobile radiators, working in closed circuits. The incoming air passes through the oils and is exposed to the ambient air. Heat transfer occurs between the water (in the coils) and air, leading to the cooler of the coils or fine tubes and hot and warm air extracted from the cooling tower to the atmosphere. Its heat transfer method is different from the rest of the cooling tower types, as there is no direct contact between water and air.
- Hybrid Cooling Towers: It has features of both wet and dry cooling towers, as the name “Hybrid” indicates. These kinds of cooling towers are very beneficial in working in almost all types of climates and conditions, as they can easily balance the water and energy levels. The ambient temperature can be varied at different times.
Advantages of Hybrid Cooling Towers
Cooling towers have multiple benefits, such as making them more efficient than other types, such as dry cooling towers. Here are the most prominent advantages of hybrid cooling towers:
- Working Flexibility
- Enhanced Water Conservation
- Eco-Friendly
- Optimum Performance
- Reduce Energy Consumptions
How to Maintain Cooling Towers for Maximum Working Efficiency?
With the passage of time and continuous work, efficiency can be reduced due to wear and gear. To avoid any interruption in the cooling process, it is critical to inspect and maintain the vital cooling tower parts and focus on whether there are signs of leaks or damage on different tower components.
- Weekly examination and removal of clogging, debris, and sediment from the fill media. Also, check the spray nozzles to ensure the water is evenly distributed.
- Determine cooling tower efficiency by ensuring adequate water temperature and level in the sump and hot water basin.
- Use the latest technology and dedicated software to track and analyse the scheduled tasks.
- Keep a record and document the previous examination to keep records and manage the cooling tower maintenance process seamlessly.
- Take immediate notice of any unfamiliar or more giant sound from the cooling tower components; in case of any damage, focus on replacing these parts by buying from trusted sellers of cooling tower parts for better efficiency and long-lasting.
Conclusion (Types of Cooling Towers)
In this age, cooling towers are essential parts of our lives; they also effectively facilitate more significant buildings, industries, and power plants. In this comprehensive informational article, we have thoroughly discussed the main types of cooling towers: natural draft cooling towers, induced draft cooling towers, forced, wet, dry, hybrid, counter flow cooling towers, and counter flow towers. It also explains how they work and their specifications, advantages, and disadvantages.
It is evident that with time and 24/7 continuous work, sometimes a cooling tower’s efficiency is reduced for different reasons; regular upkeep and timely maintenance can prevent costly repairs or replacements. When buying cooling tower parts, always prefer quality parts and search for expert dealers in the cooling tower industry to ensure excellent performance and longer life span of these components.
