Cooling Tower System Types and Applications Discussed

Cooling towers are a crucial part of many industrial processes, and understanding the different types of cooling tower systems can help you make informed decisions about your own cooling needs.

There are three main types of cooling towers: natural draft, mechanical draft, and hybrid. Natural draft cooling towers use the natural convection of air to cool the water, while mechanical draft towers use fans to force air through the system.

Mechanical draft towers are further divided into two subcategories: forced draft and induced draft. Forced draft towers use fans to push air through the system, while induced draft towers use fans to pull air through the system.

Hybrid cooling towers combine the benefits of both natural and mechanical draft systems, offering a more efficient and effective cooling solution.

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A cooling tower system is used to cool water and is a huge heat exchanger, expelling building heat into the atmosphere and returning colder water to the chiller.

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It's a crucial component in many air conditioning systems, especially in hot climates, large office buildings, hospitals, and schools.

The system receives warm water from a chiller, which is typically located at a lower level, like in a basement.

This warm water is known as condenser water because it gets heat in the condenser of the chiller.

The cooling tower's role is to cool down the water, so it can return to the chiller to pick up more heat.

It works by exposing the recirculating cooling tower water to cool, dry air, allowing heat to leave the water through evaporation.

The fan on top of the tower brings in air from the bottom and moves it up and out in the opposite direction of the warm condenser water at the top.

The air carries the heat by evaporating water from the cooling tower into the atmosphere.

A ton of air-conditioning is defined as the removal of 12,000 British thermal units per hour (3.5 kW), but the equivalent ton on the cooling tower side rejects about 15,000 British thermal units per hour (4.4 kW).

This is because the cooling tower also rejects the additional waste-heat-equivalent of the energy needed to drive the chiller's compressor.

In HVAC systems, cooling towers are often used with liquid-cooled chillers or liquid-cooled condensers to dispose of unwanted heat.

They're also used in systems with multiple water source heat pumps that share a common piping water loop.

Cooling towers are categorized based on the direction of airflow and draft. There are five main types of cooling towers used today.

The direction of airflow can be either counter or cross. In counterflow cooling towers, the air flows upward and the water flows downward. In crossflow cooling towers, the water flows vertically through the fill while the air flows horizontally.

Mechanical draft cooling towers use power-driven fan motors to force or draw air through the tower. Natural draft cooling towers utilize buoyancy via a tall chimney. Fan-assisted natural draft cooling towers are a hybrid type that appears like a natural draft setup, though airflow is assisted by a fan.

Here are the main types of cooling towers categorized by air and water flow direction:

Natural draft cooling towers are a type of cooling tower that relies on natural air convection to cool the incoming hot water. They're typically used in large industrial facilities like chemical and power plants.

These towers are designed to enhance natural air circulation patterns, making them exceptionally efficient. Their tall, open chimney-like structure helps direct the airflow upward.

One specific design of natural draft cooling towers is the hyperbolic cooling tower, which is often used at industrial facilities. Its shape helps direct the airflow upward, making it exceptionally efficient, durable, and cost-effective.

The warm, humid air in natural draft cooling towers rises due to varying density when compared to the dry, colder air outside. This creates an upwards current of air within the tower.

Cold, dry air flows naturally through the tower and comes into contact with the warm, moist air that has absorbed heat from the hot water stream. The warm air will then naturally flow up, while the cold air falls to the splash fill on the bottom of the tower.

Natural draft cooling towers are tall, with a hyperbolic shape to induce proper airflow. This design helps to remove waste heat by way of rising hot air that is then released into the atmosphere.

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Cooling towers are classified into different types based on the direction of airflow and the source of air movement. There are three main types of cooling towers: natural draft, mechanical draft, and fan-assisted natural draft.

Natural draft cooling towers use buoyancy to draw air through the tower, with warm, moist air rising due to the density differential compared to the dry, cooler outside air.

Mechanical draft cooling towers use power-driven fan motors to force or draw air through the tower, making them more efficient but also more expensive to operate.

Fan-assisted natural draft cooling towers are a hybrid type that combines the benefits of natural draft and mechanical draft cooling towers.

Crossflow cooling towers have a design where the air flows horizontally through the fill and the tower's structure, while the hot water flows downward from distribution basins.

Counterflow cooling towers have a design where the air flows vertically upward, opposite to the water flow, which makes them more frost-resistant and efficient.

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Field-erected type cooling towers are typically used in large facilities such as power plants and petrochemical plants due to their greater capacity for heat rejection.

Here's a brief summary of the different types of cooling towers:

Each type of cooling tower has its own advantages and disadvantages, and the choice of which one to use depends on the specific needs of the facility or application.

Metal cooling towers have a relatively short shelf life of up to 15 years, requiring regular maintenance to prevent leaks and downtime.

Fiberglass cooling towers offer a better alternative, but they can still develop cracks and wear over time, leading to higher maintenance costs.

A biocide, a chemical that kills troublesome microbes, is often used to control their population in cooling tower systems.

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When choosing the best material for a cooling tower, it's essential to consider the lifespan and maintenance costs. Metal cooling towers have an average shelf life of up to 15 years.

Metal cooling towers require regular maintenance with epoxy paint, sealants, and more to prevent rust and corrosion. This maintenance can lead to downtime for your business.

Fiberglass cooling towers offer a better alternative to metal but are still prone to cracks and wear. This can result in long-term higher maintenance costs.

Biocide is a chemical used to control the population of troublesome microbes by killing them.

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The hyperboloid shape has become the standard for natural-draft cooling towers due to its structural strength and minimal material usage.

This design is also known for accelerating upward convective air flow, which improves cooling efficiency. In fact, it's the reason why hyperboloid cooling towers are often used at large coal-fired power plants and some geothermal plants, not just nuclear power plants.

The first hyperboloid natural-draft cooling tower was built in 1918 at the Staatsmijn Emma by DSM, to the design of Frederik van Iterson, who took out the UK patent (108,863) for Improved Construction of Cooling Towers of Reinforced Concrete in 1916.

The hyperboloid shape is often incorrectly referred to as hyperbolic, but its unique design has become synonymous with cooling towers.

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Water treatment is crucial for cooling towers to prevent scaling and fouling. This involves filtering the water to remove particulates and dosing it with biocides and algaecides to prevent growths that could interfere with the continuous flow of the water.

A biofilm of micro-organisms such as bacteria, fungi, and algae can grow rapidly in the cooling water, reducing heat transfer efficiency. This can be reduced or prevented by using sodium chlorite or other chlorine-based chemicals.

Using two biocides, such as oxidizing and non-oxidizing types, is a normal industrial practice to complement each other's strengths and weaknesses. A continual low-level oxidizing biocide is often used, then alternating to a periodic shock dose of non-oxidizing biocides.

Maintaining suitable water chemistry is essential to prevent chemistry-related issues in the cooling tower. Employing adequate water treatment methods according to the manufacturer's specifications can help prevent problems like corrosion, scaling, bacterial and fungal growth, and increased energy consumption.

There are several heat transfer methods used in cooling towers, each with its own advantages and disadvantages. Wet cooling towers operate on the principle of evaporative cooling, where the working coolant (usually water) is exposed to the elements.

Wet cooling towers can cool water to a temperature lower than the ambient air dry-bulb temperature, but only if the air is relatively dry. Approximately 2,300 kilojoules per kilogram (970 BTU/lb) of heat energy is absorbed for the evaporated water.

Closed circuit cooling towers, also called fluid coolers, pass the working coolant through a large heat exchanger, usually a radiator. This protects the working fluid from environmental exposure and contamination.

Adiabatic cooling towers spray water into the incoming air or onto a cardboard pad to cool the air before it passes over an air-cooled heat exchanger. They use less water than other cooling towers but do not cool the fluid as close to the wet bulb temperature.

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Dry cooling towers operate by heat transfer through a heat exchanger that separates the working coolant from ambient air, utilizing convective heat transfer. They do not use evaporation and are air-cooled heat exchangers.

Hybrid cooling towers can switch between wet or adiabatic and dry operation, helping balance water and energy savings across a variety of weather conditions. Some hybrid cooling towers can switch between dry, wet, and adiabatic modes, achieving thermal efficiencies up to 92%.

To achieve better performance in wet cooling towers, a medium called fill is used to increase the surface area and the time of contact between the air and water flows. There are two main types of fill: splash fill and film fill.

Maintenance is key to keeping your cooling tower system running efficiently. Regular checks of water quality, specifically aerobic bacteria levels, should be taken using dipslides to prevent the growth of legionella.

To prevent freeze damage, some cooling towers are shut down seasonally, drained, and winterized. Basin heaters, tower draindown, and other freeze protection methods are often employed in cold climates.

Here are some procedures to prevent freezing:

A cooling tower's primary function is to cool down water by expelling building heat into the atmosphere, returning colder water to the chiller. This process is crucial for air conditioning equipment and industrial processes that generate heat.

The cooling tower receives warm water from a chiller, which is then cooled down through evaporation, a process known as evaporative cooling. Heat leaves the recirculating cooling tower water through evaporation, allowing the water to reenter the air conditioning equipment or process to cool it down.

The fan on top of the water cooling tower brings in air from the bottom of the tower and moves it up and out in the opposite direction of the warm condenser water at the top of the unit. This helps to carry the heat away from the cooling tower into the atmosphere.

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A cooling tower's material balance is governed by operational variables such as make-up volumetric flow rate, evaporation and windage losses, draw-off rate, and concentration cycles. The evaporated water has no salts, and a chloride balance around the system shows that the concentration of chlorides in the circulating water is equal to the concentration of chlorides in the make-up water multiplied by the cycles of concentration.

Windage (or drift) losses are the amount of total tower water flow that is entrained in the flow of air to the atmosphere. In large-scale industrial cooling towers, windage losses can be assumed to be around 0.2-0.5% of the total water flow.

Here's a breakdown of the common cooling system terms:

Maintaining water chemistry is crucial for the proper operation of a cooling tower. This involves regularly monitoring and adjusting the levels of disinfectant and other chemicals in the system.

Disinfectant and chemical levels should be continuously maintained and regularly monitored to prevent the growth of microorganisms. You can do this using dipslides to check aerobic bacteria levels.

To prevent scaling and fouling, circulating cooling water should be treated to minimize these issues. This can be done by filtering the water to remove particulates and dosing it with biocides and algaecides.

Regular checks of water quality are essential to prevent the growth of bacteria, fungi, and algae. You can use sodium chlorite or other chlorine-based chemicals to reduce or prevent biofilm growth.

Employing adequate water treatment methods according to the manufacturer's specifications is necessary to prevent chemistry-related issues in your cooling tower. This can help prevent costly repairs and ensure efficient operation.

Cooling towers can be a significant source of water waste if not properly maintained. Water leaks are a common issue that can be challenging to resolve.

Many utilities across North America offer evaporative cooling credits for the monitoring of cooling towers. These credits incentivize the use of systems that enhance water efficiency by providing financial benefits for implementing advanced monitoring and conservation measures.

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Wint Water Intelligence offers a dedicated solution to prevent water waste in cooling towers. It lets you monitor water use at the cooling tower and alerts you when water waste is detected.

A smart water management solution like Wint can be particularly valuable to increase water efficiency and take advantage of utility incentives. This can potentially save you huge expenses on damage repairs and water waste.

Real-time leak detection technologies like Wint can automatically stop water leaks by remotely shutting off the valve at the source. This can prevent costly repairs and water waste.

Higher energy efficiency is a significant benefit of water-to-air heat transfer, which reduces electricity demand for cooling and translates to lower costs and power bills.

Modern cooling towers can be customized and optimized with smart and connected IoT devices, aligning energy consumption with required cooling output.

These systems provide real-time data and predictive analytics, improving process controls and enhancing operational efficiency.

Cycles of concentration play a crucial role in cooling tower performance. In most cooling towers, cycles of concentration range from 3 to 7.

The amount of dissolved minerals in make-up water can vary significantly, affecting the cycles of concentration. Make-up waters from surface water supplies, such as lakes and rivers, tend to be aggressive to metals due to their low mineral content.

Increasing the amount of minerals present in the water can make it less aggressive to piping, but excessive levels can cause scaling problems. This is why it's essential to strike a balance.

A professional water treatment consultant can evaluate the make-up water and cooling tower operating conditions to recommend an optimal range for the cycles of concentration. They may also suggest using water treatment chemicals, pretreatment, or other techniques to achieve this balance.

In the United States, many water supplies use well water with significant levels of dissolved solids, resulting in lower acceptable ranges for cycles of concentration. On the other hand, cooling towers in cities like New York City, which have a surface rainwater source with low minerals, can often concentrate to 7 or more cycles of concentration.

The natural effect of water-to-air heat transfer drastically reduces the electricity demand for cooling. This reduction translates to lower costs, lower power bills, and a decrease in your building's carbon footprint.

Modern cooling towers enable great customization and optimization with smart and connected IoT devices. These systems align the energy consumption of the pumps and fans with the required cooling output.

Advancements in IoT devices provide real-time data and predictive analytics, improving process controls and enhancing operational efficiency.

Cooling towers play a crucial role in keeping our water clean and safe.

Regular maintenance is key to preventing bacterial growth in cooling towers, which can lead to Legionnaires' disease.

The ASHRAE 188-2015 standard sets minimum requirements for the control of Legionella in cooling towers, including regular water sampling and treatment.

Bacterial growth can be prevented by ensuring the cooling tower's water temperature is kept between 73°F and 80°F, as mentioned in the "Cooling Tower Water Temperature" section.

Legionnaires' disease is caused by the inhalation of mist droplets containing Legionella bacteria. This bacteria thrives in warm, wet conditions, making water cooling towers an ideal environment.

Legionella bacteria can be found in various sources, including cooling towers, domestic hot water systems, fountains, and natural sources like freshwater ponds and creeks.

In fact, studies have found Legionella in 40% to 60% of cooling towers. This highlights the importance of proper maintenance and treatment of cooling towers to prevent the growth of Legionella.

The most common species of Legionella that causes legionellosis is L. pneumophila, which can be transmitted through aerosols. This is why it's essential to use biocides in cooling towers to prevent the growth of Legionella.

A 2017 study by the CDC found six Legionnaires' outbreaks in New York City that resulted in 213 cases and 18 deaths. Three of those outbreaks were linked to cooling towers, emphasizing the severity of the issue.

Here are some common sources of Legionella:

Salt emission pollution is a serious concern, especially in coastal areas where wet cooling towers with seawater make-up are installed. The drift of fine droplets emitted from these cooling towers contains nearly 6% sodium chloride, which can deposit on nearby land areas and convert them into sodic saline or sodic alkaline soils.

Respirable suspended particulate matter, specifically PM10, can be present in the drift from cooling towers and settle in the bronchi and lungs, causing health problems. Particles smaller than 2.5 μm, or PM2.5, can penetrate into the gas exchange regions of the lung. Very small particles, less than 100 nanometers, may pass through the lungs to affect other organs.

The salt content in the drift from cooling towers with seawater make-up is much higher than those with fresh water make-up, at 60,000 ppm compared to below 2,000 ppm. This is because seawater contains more salt than fresh water.

Cooling towers are cost-effective and highly sustainable air cooling systems. They are a great alternative to other types of cooling solutions.

One of the main advantages of cooling towers is that they are cost-effective. This is because they use a lot less energy than traditional air conditioning systems.

Cooling towers are highly sustainable, making them a great choice for environmentally conscious building owners. They reduce the amount of greenhouse gas emissions and help to minimize the carbon footprint of a building.

Regardless of the type, make or model, cooling towers are a reliable and efficient way to cool buildings. They can be used in a variety of applications, including industrial, commercial, and residential settings.

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Regular maintenance is crucial for cooling tower systems to prevent issues and ensure efficient operation.

Clean visible dirt and debris from the cold water basin and surfaces with any visible biofilm, also known as slime.

Disinfectant and chemical levels in cooling towers and hot tubs should be continuously maintained and regularly monitored.

Regular checks of water quality, specifically aerobic bacteria levels, using dipslides are essential to detect the presence of other organisms that can support legionella.

Mechanical malfunctions in cooling towers can be relatively easy to detect but expensive to resolve, so it's essential to keep a regular maintenance schedule to minimize malfunction risks.

Check the water levels and quality to spot any signs of contamination, and review the performance of fans, valves, and pumps if there are temperature issues.

Proper Cycles of Concentration (CoC) management optimizes water use and minimizes waste, and tools like thermometers can help identify specific problems.

The cooling tower industry has evolved significantly over the years, with various technologies being developed to improve efficiency and reduce environmental impact. A typical 700 MWth coal-fired power plant circulates about 71,600 cubic meters of cooling water per hour.

Large industrial facilities, such as power plants and refineries, often rely on cooling towers to dissipate heat into the atmosphere, spreading it over a larger area than hot water can. This is particularly important for plants located near water sources, as it helps to prevent thermal pollution and kills millions of fish and larvae annually.

Industrial cooling towers can be used to remove heat from various sources, including machinery and heated process material, with some plants requiring a supply water make-up rate of up to 5 percent. In comparison, once-through cooling water systems can require up to 100,000 cubic meters per hour, which would need to be continuously returned to the ocean, lake or river.

As the world's population grows, so does the demand for manufactured products, forcing the industrial sector to produce more and more every day. This leads to a huge increase in manufacturing process heat.

Industrial machines and processes generate tremendous amounts of heat that must be continuously cooled to operate efficiently. The machines in power plants, petroleum refineries, and petrochemical plants are just a few examples that require cooling.

The increased heat generation is a result of the world's growing need for manufactured products. This has made it essential for industries to install industrial cooling towers to remove heat efficiently.

Industrial cooling towers are critical components in various industries, including power plants, chemical processing, and steel mills. They also provide comfort-cooling for large commercial buildings like airports and hospitals.

Industrial cooling towers are a crucial part of many industrial facilities, including power plants, petroleum refineries, and petrochemical plants. They help remove heat from circulating cooling water systems, which is essential for maintaining equipment efficiency and preventing overheating.

A typical 700 MWth coal-fired power plant circulates about 71,600 cubic meters of water per hour through its cooling tower. This is a massive amount of water, equivalent to one cubic meter every second.

The primary use of industrial cooling towers is to remove heat from various sources, including machinery and heated process material. They are also used in condensers of distillation columns and for cooling liquid in crystallization.

Large industrial cooling towers can be very tall, like the 210 meters (690 ft) tall cooling tower of the Pingshan II Power Station in Huaibei, Anhui Province, China. This tower is the world's tallest cooling tower.

Industrial cooling towers can dissipate heat into the atmosphere, spreading it over a much larger area than hot water can. This is a more efficient and environmentally friendly way to cool large industrial facilities.

Petroleum refineries, for example, may circulate up to 80,000 cubic meters of water per hour through their cooling tower systems. This is a huge amount of water, and it's essential for maintaining the refinery's equipment and preventing overheating.

The use of industrial cooling towers can also help reduce the environmental impact of industrial facilities. By dissipating heat into the atmosphere, they can prevent thermal pollution and reduce the amount of hot water discharged into bodies of water.