What is The Purpose of Fill in a Cooling Tower?

Cooling towers are an integral component of many industrial and commercial facilities. They serve the important purpose of removing excess heat from industrial processes or air conditioning systems. In order to achieve this, cooling towers rely on a process of evaporation and heat transfer. However, in order for cooling towers to function properly, they require fill. In this article, we will explore the purpose of filling in a cooling tower.

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What is fill in a cooling tower?

Fill refers to the material that is used to fill the space inside a cooling tower. The fill is a critical component of the tower because it provides a large surface area for water to flow over, which facilitates the transfer of heat from the water to the air. Fill is typically made of PVC or another plastic material, and it is designed to be lightweight and durable.

The purpose of filling in a cooling tower

The primary purpose of filling in a cooling tower is to increase the surface area of the water that is exposed to the air. As water flows over the fill material, it spreads out into a thin film, which allows for maximum contact with the air. This increased surface area maximizes the amount of heat that can be transferred from the water to the air.

The fill material also creates a large amount of turbulence in the water as it flows through the tower. This turbulence helps to break up any stagnant areas within the water and ensures that all parts of the water are exposed to the air. This, in turn, improves the overall efficiency of the cooling tower.

Another important purpose of filling in a cooling tower is to minimize the amount of water that is lost through evaporation. When water is sprayed onto the fill material, it is broken up into droplets, which helps to minimize the amount of water that is lost through evaporation. This is important because evaporation can be a major source of water loss in a cooling tower, and minimizing this loss can help to reduce operating costs.

Types of fill

There are two main types of fill that are commonly used in cooling towers: film fill and splash fill. A film fill is a type of fill that is designed to create a thin film of water over the surface of the fill material. This film allows for maximum contact between the water and the air, which maximizes the efficiency of the cooling tower. Splash fill, on the other hand, is designed to break up the water into small droplets as it flows over the fill material. This creates a large amount of turbulence within the water and ensures that all parts of the water are exposed to the air.

What to Consider When Purchasing Cooling Tower Fill

If you’re in the market for cooling tower fill, choosing the right type is critical to ensure optimal system performance and long-term reliability. Here are key factors that industrial buyers and engineers should consider:

1. Material Type

Different materials serve different working environments:

• PVC (Polyvinyl Chloride): Offers good chemical resistance and is cost-effective. It is used in over 80% of standard cooling tower installations, especially in HVAC and light industrial applications.

• PP (Polypropylene): Can withstand higher temperatures (up to 100–120°C compared to PVC's ~60°C). Ideal for applications with hot process water or strong chemicals.

• Wood or Metal Fill: Less common today but still in use for legacy systems or high-load industrial cooling towers.

We offer a wide range of fill materials – click here to view all fill products.

2. Fill Type and Structure

• Film Fill: Designed with thin corrugated sheets that create a large surface area for water film formation. This type can improve heat exchange efficiency by up to 30% in clean water systems.

• Splash Fill: Breaks water into droplets and resists fouling—ideal for systems using untreated or recirculated water. Increases system reliability in high-dust or sediment-prone environments.

• Modular Block Fill: Used in regions where maintenance access is limited. Reduces cleaning time by 40–60% compared to traditional sheet fill.

Each fill type optimizes efficiency and operational stability depending on water quality and system type.

3. Thermal Performance & Efficiency

Ask for the KaV/L value—a widely recognized metric for fill thermal performance:

• KaV/L ≥ 0.2 is considered high-performance for standard industrial applications.

• Using high-efficiency fill can reduce outlet water temperature by 2–5°C, resulting in:

• 5–15% lower chiller energy consumption

• Better equipment lifespan and reduced operational load

We provide thermal performance data sheets on request for all our fill products.

4. Size & Customization

• Fill packs are available in various lengths (0.5–2 meters), thicknesses (100–600mm), and flute sizes (12–30mm) to match different tower models and flow rates.

• We support custom designs for non-standard towers or space-limited installations.

Need a custom fill pack? Contact us now to discuss your project needs.

5. Durability and Maintenance

• Average service life ranges from 3 to 7 years, depending on material, operating temperature, and water quality.

• Using UV-resistant and anti-microbial additives can extend service life by up to 20–30% in outdoor or high-temperature environments.

• For towers in regions with hard water or dust, modular fill design reduces cleaning downtime by up to 50%.

Long-term performance means fewer replacements and lower lifecycle cost.

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6. Compatibility

Ensure the fill is compatible with:

• Your cooling tower configuration: Crossflow or Counterflow

• Water treatment process and filtration level

• Airflow pattern and spray system

Not sure what you need? Our technical engineers provide free evaluation reports based on your tower specs.

Conclusion

Cooling towers are used to remove heat from water used in water-cooled applications. The heat is rejected to the atmospheric air that is passed through the system fill in a crossflow or counterflow method. A small percentage of the hot water from the system evaporates, cooling the remaining water which falls into the cold-water basin which is then pumped from the cold water basin to the system to absorb more heat in a continuous process. 

It’s important to consider the efficiency of the cooling towers ability to reject heat for your project requirements. When you have the project requirements in the way of total tons, range and approach, then you can begin to analyze the cooling towers that would be appropriate for your water-cooled application. 

Induced draft crossflow and counterflow cooling towers both offer advantages and disadvantages based on specific project requirements and site conditions. 

The obvious difference is in the method by which the air moves through the cooling tower in relationship to the cooling water, which is indicated by its description of a being crossflow or counterflow.

With a crossflow tower the air travels horizontally perpendicular) to the water traveling vertically down to the cold basin. With a counterflow cooling tower, air travels in the opposite direction vertically upward against the stream of falling water.

Cooling Tower Footprint – Physical Size 

Air is required in sufficient amounts to accomplish the heat transfer requirements at the design conditions and at varying amounts for less than design conditions. Consideration must be made for this volume of air and the space required in the design of the tower to ensure the proper volume of air effectively interacts with the cooling water. 

Cooling tower manufactures will have different footprint thresholds where the vertically configured counterflow goes from the smaller footprint to the larger footprint. Because of the nature of the counterflow tower where the air and water interact vertically, this allows for a smaller footprint most of the time in towers around 800 tons or less. As cooling towers get larger than 800 tons, the advantage could switch to counterflow.  

Site conditions will determine whether the physical size of the cooling towers footprint is more important, or any height restrictions imposed by site factors. 

Maintenance

In order to keep the cooling tower operating for efficiently and for its useful life it’s important to provide periodic maintenance. This will require that you consider tower access as a factor in the design and location of the tower. 

Access to the internal working parts various between the two designs. With the crossflow tower most of the internal parts are easily accessible as the fill material surrounds the exterior portions of the insides, allowing for access to the fan, motor, drift eliminators and cold-water basin. With larger crossflow cooling towers, the manufactures have an option to have ladders and platforms preinstalled for easy access to the motor and drive. 

Access to the components of a counterflow tower are less friendly to the maintenance personnel because the overhead horizontal fill material provides a barrier between various components. The fan, motor, eliminators and spray system have limited access because they are located above the horizontal fill making then inaccessible from the cold-water basin.  

Cooling Tower Operating Weight

Because of the crossflow towers larger footprint, it’s shipping and operating weight will often be greater than that of the counterflow tower. The bigger footprint of the counterflow tower can require additional structural support legs. 

Water Distribution – Pressurized or Gravity

With the crossflow tower there is a hot-water basin above the fill that distributes the water that is pumped to the top of the tower. The water in the hot-water basin than makes its way through the distribution nozzles by gravity without the force of the pump. This allow for easier maintenance of the nozzles since the water is gravity fed and out of the air stream. 

The design of the counterflow tower and the method by which the water descends in direct opposition to the vertically induced air, necessitates the need to pressurize the water distribution. Since the water is under pressure through the nozzles this requires that you shutoff the pump in order to clean or service the distribution system. 

Another design and maintenance consideration are the method by which the water is distributed over the fill material. 

Cooling Tower Capacity and Energy Efficiency 

With many jurisdiction and states increasing energy efficiency requirements, the use of variable flow increases energy savings. As the tonnage requirement drops it’s wise to have the tower vary is flow in order to save energy. 

Capacity can be increased basically three different ways. One way is by increasing the footprint of the tower, the second method would be to increase its height, and the third way would be to increase the HP of the fan motor to get more CFM out of the same tower size before having to go to the next size tower. These are some of the decisions that will need to be made based on project conditions.

• Increase Footprint (additional heat transfer surface area) #1 in image below
• Increase Height (additional heat transfer surface area) # 2 in image below
• Increase Fan HP (more CFM) #3 in image below

Crossflow cooling towers are better at turndown than counterflow because of the inherent features of their water distribution methods. 

Cooling towers are rated based on standard conditions of 95ºF (35.0ºC) entering water temperature to an 85ºF (29.4ºC) leaving water temperature at a 78ºF (25.6ºC) entering wet-bulb temperature. This correlates to 3 GPM of water per nominal ton. For non-standard conditions seek the assistance of your local cooling tower sales representative and their access to tower sizing software.  

Cooling Tower Fill – Heat Transfer Surface

Cooling tower manufactures offer options on the type of fill based on factors such as the condition or chemistry of the water and the potential for biological growth. It’s important to prevent scaling which will reduce the capacity and ability of the tower to efficiently reject heat. 

The use of PVC for fill material is common due to its low cost and effectiveness in clean water applications. If the water quality is not satisfactory than the use of splash fill might be required which will also increase the cost due to it be less efficient at heat transfer, which will also increase the size of the tower to meet the same project requirements. The use of splash fill is less prone to clogging due to dirty water as opposed to PVC Film which can clog more easily. 

Cooling Tower Fans

There are anywhere from one or more fans that provide for the air movement through the towers. The most energy efficient being the axial fan which sits at the top of the tower. The use of centrifugal fans are more commonly used in forced draft fluid coolers. 

Summary

Your project requirements and site conditions will determine the best option of either a crossflow or counterflow cooling tower including any consideration for maintenance. 

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