Everything You Need to Know About Cooling Towers
What do you know about cooling towers? You might have come across a cooling tower but are yet to comprehend fully what it entails. You could be looking for information such as; “what do cooling towers do, or who uses cooling towers”. Well, you are in the right place. Below is a comprehensive guide to cooling towers.
What is a cooling tower?
If you are wondering what cooling towers do and what they are, this information is for you. A cooling tower is a device used to lower the temperature of water used in industrial processes. The device is a unique type of heat exchanger that uses air to cool the water through evaporation.
A cooling tower can be used in various industrial applications such as:
- Power plants
- Gas refineries
- Petrochemical plants
- HVAC
- Steel mills
How do cooling towers work?
You might be wondering how cooling towers work to streamline industrial cooling processes. Let us address the working principle of a cooling tower.
Hot water from industrial processes is pumped into the cooling tower and exposed to dry air, which removes the heat from the water by evaporating the excess heat. The cool water is then pumped back into the industrial equipment or HVAC system and the cycle continues.
The cooling tower has nozzles, and a medium inside referred to as the “fill”. Materials such as PVC sheets are used to create the cooling tower fill. The water enters the fill through the nozzles which release the water in small droplets. The fill increases the surface area of the water to let the air cool the water more effectively through vaporization.
The air is drawn in using a fan on top of the cooling tower. The air passes through the water and removes excess heat in the water through evaporation, which is released into the atmosphere.
Parts and functions of a cooling tower
A cooling tower has several parts that streamline the cooling process. Below are some of the parts and functions of common industrial cooling towers.
Gearbox
The gearbox is used to regulate the fan speed of industrial cooling towers. There are different types of gearboxes used in cooling towers which include:
- – A series single reduction gearbox
- – A series double reduction gearbox
- – Single reduction gearbox
Cooling tower fill media
The cooling tower fill media is a component that is used to increase the surface area between the two fluids for effective heat transfer. The fill is designed to expose the hot water to dry air for an extended period to allow heat extraction through evaporation. The cooling tower film media is commonly available in two types namely:
- 1. Splash style fill media
- 2. Film style fill media
Cooling tower fan
A cooling tower fan is a component that is used to force air into the cooling tower for maximum cooling of water. Quality cooling tower fans are built to withstand harsh atmospheric conditions that could cause corrosion and reduce the effectiveness of cooling towers. These fans are used in different types of cooling towers such as:
- – Cross-flow
- – Counter flow
- – Mechanical draft
Nozzles
Nozzles are components of industrial cooling towers that regulate the distribution of water to promote efficient heat transfer. The nozzles distribute droplets of water to the fill media in proportionate amounts to the air, to maximize evaporation.
Air intake louvers
Air intake louvers are cooling tower components whose function is to block debris, sunlight, and noise from getting into the cooling tower basin. The air intake louvers also prevent water from splashing out of the cooling tower. This in turn helps maintain the level of water and prevents you from incurring more costs spent on chemicals.
The air intake louvers also prevent mold and algae growth in the towers by blocking sunlight. A reliable cooling tower manufacturer can advise you on how to properly maintain your air louvers to increase the effectiveness of your cooling tower.
Drift eliminators
Drift eliminators are used to minimize water loss due to evaporation. The drift eliminators preserve water by redirecting the moist air to another direction other than the intended and further separating the air from water droplets. The recovered water can then be recycled in industrial processes.
Motor
Cooling tower motors are components of some types of towers used to drive the fan. There are two types of motors namely open and enclosed motors. A cooling tower manufacturer can help you select a cooling tower with a durable motor that can withstand harsh conditions.
Types of cooling towers
These towers can be categorized according to heat transfer method, airflow process, and build. Below are the different types of towers.
Heat transfer method
Below is a classification of cooling towers by their heat transfer techniques.
Wet cooling towers
Also called open-circuit cooling towers, they use air to cool water in HVAC systems and industrial processes. The water and air are in direct contact where the air is used to reduce heat by evaporation creating a cooling effect in the water.
Dry cooling towers
These towers use air to cool the fluid, which can be water The fluid passes through tubes in the cooling tower, and the surrounding cool air extracts the heat from the fluid. This type of cooling tower does not use evaporation to cool the fluid, and the two fluids don’t mix hence the term dry cooling tower. This type of cooling tower is suitable for applications where water resources are scarce.
Fluid coolers
In fluid coolers, there is no direct contact between the fluid and air. In fluid coolers, the hot fluid passes through tubes. Cold water is then sprayed on these tubes combined with cool air to extract heat from the fluid. This technique can be applied in HVAC cooling towers. For instance, it can be used in commercial air conditioning.
Airflow process
Below are the common types of towers classified according to their airflow process.
Crossflow cooling towers
In these towers, the two fluids flow perpendicularly to each other. The hot water flows downward while the cool air flows horizontally. This type of cooling tower is easy to maintain and cost-friendly. However, these models can collect debris and dirt due to their design.
Counter flow cooling towers
A counter flow cooling tower features two fluids that enter through opposite sides and move towards each other. The water flows downwards, and the air moves upwards to necessitate heat transfer. This type of airflow makes the cooling tower more efficient and compact compared to other types of towers.
Airflow generation
The methods used to introduce air into cooling towers make them different. Below are the various airflow generation methods.
Natural draft
This type of cooling tower relies on natural convection to produce a cooling effect. Since warm air is less dense than cold air, it travels upwards while the cool air and water stay at the bottom of the cooling tower. This type of cooling tower does not use fans to enhance heat transfer.
Mechanical draft
Mechanical draft cooling towers use mechanical fans and other mechanisms to create air circulation in the cooling tower. These towers can use centrifugal or propeller fans to necessitate heat transfer. This type of cooling tower is more effective than a natural draft cooling tower. However, mechanical draft towers can be costly because they require a lot of power to operate.
Induced draft
An induced draft cooling tower is a type of mechanical cooling tower whose fans are located at the top of the tower. These fans pull the air into the cooling tower to facilitate heat transfer between the two fluids. Induced draft cooling towers ensure efficient transfer by getting rid of warm unwanted air from the tower to reduce recirculation.
Forced draft
This is a type of cooling tower whose fans are located at the air intake position. The fans can be positioned at the bottom of the tower. Unlike induced draft cooling towers, a forced draft cooling tower pushes the air upward into the cooling tower to facilitate the heat transfer process.
Cooling towers that implement forced draft can last longer than those with the induced draft. This is because cleaner air at the bottom is less likely to corrode the fans compared to the warm air at the top. Forced draft cooling towers are also affordable. However, they require more power than induced draft towers.
Method of assembly
Cooling towers can also be classified according to their build or method of construction. Below are the different builds of cooling towers.
Factory-assembled cooling towers
Factory-assembled cooling towers are constructed by cooling tower manufacturers in a factory and shipped after complete assembling. These cooling towers are mostly compact and are used in applications that don’t require large-scale cooling. For instance, HVAC cooling towers can be factory assembled.
Field-erected cooling towers
Field-erected cooling towers are assembled on site. Some industrial factories require large cooling towers because they produce a lot of heat. Such industries include power plants, oil refineries, etc. the cooling tower parts are shipped and assembled by cooling tower manufacturers on site.
Factors affecting cooling tower performance
Below are some factors that affect the performance of your cooling tower.
Cooling range
The cooling range is the difference in temperature between the hot water entering the cooling tower and the cold water exiting the tower.
Fill media condition
Well-maintained fill media ensure proper water-air contact and optimal cooling performance.
Wet bulb temperature
This is the ambient air temperature which is measured by covering the thermometer with water and exposing it to air. The thermometer used to measure wet bulb temperature is known as a psychrometer.
Ambient Temperature
Higher ambient temperatures can affect the tower’s ability to cool water efficiently.
Approach
This is the temperature difference between the water leaving the cooling tower and the wet bulb temperature of the air entering the tower. When the wet bulb temperature decreases, the temperature of the cool water exiting the tower also decreases.
Heat load
Heat load is the amount of heat extracted from the water in the cooling tower. The heat load also determines the tower cost and size. When the cooling demand is low, the cooling tower operates at a lower efficiency.
Airflow rate and water flow rate
A higher water flow rate through the tower generally improves cooling performance. The amount of airflow through the tower affects the rate of evaporation and thus the cooling capacity.
Mechanical maintenance practices
You should consider regularly inspecting your cooling tower to increase efficiency and improve performance. Routine maintenance can also help you reduce repair costs. The following is a maintenance checklist for your cooling tower.
- – Examine the cold water basin for any damage like cracks
- – Clean the cold water basin and get rid of any debris, dirt, algae, or mold
- – Check for clogs in tubes and regularly clean the pipes to remove any dirt or debris
- – Remove fouling, scaling, and mineral deposits in the fill
- – Check for cracks on the fan deck and adjust your fan blades
- – Inspect your nozzles and flow valves and check for clogs
- – Examine the water level in the cold water basin
- – Check your drift eliminators and ensure they are clean and positioned properly.
- – Ensure your bearings are properly lubricated
- – Check for leaks in the pipes and valves
- – Conduct routine backwashing for cooling towers with side stream filters
- – Inspect and regularly clean your water pump
Energy Efficiency and Environmental Impact
Improving Energy Efficiency
Upgrading to more efficient fans, optimizing water flow rates, and implementing smart control systems can significantly improve cooling tower energy efficiency.
Water Conservation
Water conservation measures, such as reducing bleed and evaporation losses, can minimize water consumption and contribute to sustainability efforts.
Minimizing Chemical Usage
Efforts to minimize chemical use while still ensuring effective water treatment can reduce environmental impact and operational costs.
Environmental Regulations and Compliance
Understanding and adhering to local and regional environmental regulations are essential for responsible cooling tower operation.
Safety Considerations
Hazards and Risks
Cooling towers pose certain risks, such as falling from heights during maintenance, exposure to hazardous chemicals, and potential legionella contamination.
Safety Equipment and Procedures
Proper safety equipment, such as personal protective gear, fall protection systems, and emergency shut-off mechanisms, should be in place to protect workers.
Training and Emergency Plans
All personnel working with or around cooling towers should receive proper training on safety protocols and emergency procedures.
Water treatment
Contaminated water in cooling towers can cause fouling, scaling, and corrosion which can affect the performance of your cooling tower. Microbes and mineral deposits can also cause health-related issues when they build up.
Out of 194 cooling towers tested for this bacteria, 84% showed positive results. Regularly testing for contaminants and treating your water can prevent the above issues and risks. You can opt to outsource a cooling tower expert to test and get rid of contaminants in your water. There are several methods of water treatment that you can use depending on your needs. They include:
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- – Water softening
- – Blowdown and makeup water
- – Chemical treatment (biocides, corrosion inhibitors, scale inhibitors, algaecides)
- – Filtration and ultrafiltration
- – Check for cracks on the fan deck and adjust your fan blades
- – Side-stream filtration
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Cooling towers are major components of industrial processes. Their primary function is to cool overheated water from industrial operations and HVAC systems. There are different types of cooling systems in the market. A licensed cooling tower manufacturer like Al Tabreed can help you settle on the most suitable cooling tower. For more information, get in touch with us today.
Troubleshooting Common Cooling Tower Issues
Scale and Deposits
Scale and deposits on fill media and other components can reduce heat transfer efficiency. Descaling and cleaning procedures can resolve this issue.
Microbiological Growth
Bacterial and algae growth can cause clogging and reduce cooling efficiency. Proper water treatment and regular cleaning can address this problem.
Corrosion
Corrosion can damage tower components and reduce their lifespan. Appropriate material selection and water treatment can prevent corrosion.
Poor Cooling Performance
Various factors, such as low airflow or inadequate water distribution, can lead to poor cooling performance. Identifying the root cause and taking corrective actions can improve cooling tower efficiency.
Future Trends in Cooling Tower Technology
Advancements in Design
Advancements in cooling tower design may lead to more efficient heat transfer and reduced energy consumption.
Smart and IoT Integration
Integrating smart technologies and the Internet of Things (IoT) can enable real-time monitoring and optimization of cooling tower performance.
Sustainable Cooling Solutions
The industry may explore more sustainable cooling solutions, such as hybrid cooling systems, to reduce water usage and environmental impact.
