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.

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.

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The Ultimate Guide to Choosing radar flow meter
10 Advantages of Using Induction Heating in Manufacturing

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Conclusion

Cooling towers are an essential component of most industrial and commercial facilities. They cool water used for a variety of processes and applications. In a future post, we will be discussing the role cooling towers play in your facility’s sustainability efforts, but today we want to answer the question: how do cooling towers work? Let’s start with the basics.

The Fundamentals of How Cooling Towers Work

Cooling towers are specialized heat exchangers that are designed to remove waste heat by creating steam. Their function is to pull heat from the water and return cold water to cool down industrial equipment. In a cooling tower, heat is transferred via sensible heat and latent heat.

• Sensible heat: heat transfer related to changes in water temperature
• Latent heat: heat transfer related to changes in physical state

With cooling towers, most of the heat is transferred to the atmosphere through recirculating cooling water evaporation. Evaporative cooling is frequently used to remove large quantities of heat from processes, equipment, and living spaces. This is shown in the following Heat Transfer Equation:

Q = LHe x m

Where:   Q = evaporative heat (heat loss)

                LHe = latent heat of vaporization/evaporation of water (Btu/lb.)

                m = mass of water

The Role of Water in the Cooling Process

Water is used as the medium in cooling towers. A relatively large quantity of heat is released (1,000 Btu’s) for every pound of water evaporated. When dealing with water, heat transfer is approximately 1,000 times more efficient through evaporation versus sensible heat. The actual value is slightly lower (970.4 Btu’s), but throughout the industry, the 1,000 Btu per pound value is universally accepted.

Cooling towers are designed to create effective heat transfer by connecting air and water in an efficient and expedient manner. Anywhere from 75–95 percent of the heat from the process, equipment, or buildings is removed through evaporation and only 5–25 percent is removed via convection.

The concept of wet bulb and dry bulb temperatures should be considered. Wet bulb temperature is defined as the lowest water temperature at which heat can be removed via evaporation. The lower the wet bulb temperature, the lower the relative humidity, and the more efficient the cooling tower is at heat removal.

Cooling Tower Designs

There are three different tower designs. The right type is determined based on the size of the system/application, geographical location/climate, water quality, and local utility costs.

• Natural draft: large hyperbolic, typically found at power plants
• Cross-flow: induced draft or forced draft
• Counter-flow: induced draft or forced draft

Evaporation

When the recirculating water in a cooling tower evaporates, it theoretically exits as a pure vapor. An extremely small percentage of this vapor carries tiny water droplets containing dissolved solids. This is known as cooling tower drift. At this early point in our discussion, cooling tower drift will be considered out of scope.

Cycles of Concentration

The sequential diagrams in Figure 1 illustrate what we mean by cycles of concentration. As more water is evaporated, the quantity of dissolved solids stays consistent, so their concentration increases.

Cooling Tower Approach

• The difference between the cold sump temperature and the wet bulb temperature is called the cooling tower approach.
• The temperature difference between the hot return water and the cold sump water is referred to as the cooling range (ΔT).

Evaporation Equation

The equation in Figure 2 helps determine how much water is being evaporated (E) in terms of gallons per minute.

Note: The term ΔT is the actual measured temperature drop across the tower and not the design temperature.

Cooling Tower Internals

Counter-Flow

Hot return water and air flow are in direct opposition to each other. Drift eliminators introduce a difficult path for water droplets to navigate. Most water droplets cannot find their way to the atmosphere and fall back into the cooling tower basin, leading to decreased annual water consumption.

Splash-Fill

Although it is not considered the most efficient, splash-fill is still used in many applications, including poor quality makeup water or towers serving applications with a high potential for cooling water process contamination. Under these conditions, the higher efficiency fill may foul and require frequent chemical cleanings.

Film-Fill

Film-fill is most frequently used and widely known. It is the familiar PVC-type construction, with the characteristic waffle pattern that spreads the cooling water over a larger surface area for contact with the circulating air flow. Film-fill can be used in applications where the makeup water quality is good and hot return water temperatures never exceed 140°F. 

Cooling Tower Mass Balance Calculations

In addition to the equations below, cycles of concentration (COC) can also be calculated by using the ratio of makeup water to blowdown.

Evaporation (gpm)

Recirculation Rate (gpm) x ΔT x Ef / 1,000

Makeup (gpm)

MU = Evap (gpm) x (C/(C-1))

C = cycles of concentration, commonly determined by either:

cooling tower chloride/makeup water chlorides concentration

or

Cooling tower magnesium/makeup water magnesium concentration

Use magnesium if chlorine, hypochlorite, bromine, or chlorine dioxide is used as an oxidizing biocide.

• Blowdown = Makeup – Evaporation (all in gpm)

• Bleed (Intentional Water Loss) = Blowdown – Drift
  • Drift = 0.01 to 0.3% for mechanical draft towers
  • Drift = 0.3 to 1.0% for natural draft towers

• Half Life (Holding Time Index) (hr.) = 0.693 x V/BD (time to 50% depletion)

• Half Life (hr.) = 2.303 x V/B x Log10 Ci/Cf
  • V = System Volume
  • BD = Blowdown
  • Ci = Initial additive concentration

Cf = Final additive concentration

Choosing the Right Location for Your Cooling Tower

If possible, adhere to the following recommendations when choosing a cooling tower location:

• Do not place near contaminant sources
• Place where sump can be easily cleaned
• Avoid dead legs to reduce potential deposits and corrosion
• Minimize sunlight to reduce potential algae growth
• Add side-stream filters to remove solids (5–7% of flow)

Free-Cooling System

Through manipulation of condenser and chilled water header isolation valves, the system can be set up to have cooling tower water flow bypass the chiller (which is secured/not running) and flow directly through the chilled water piping/coil to the air handler.

The water from the air handler is then returned to the cooling tower to repeat the cycle. Not running the chiller compressor and chilled water loop circulation pumps helps conserve electrical power usage. The required outside ambient air temperature for free cooling is 40–45°F.

General Operational Guidelines

• Maintain flow through off-line equipment or remove it from service properly
• Stop process leaks quickly
• Aim to stay within recommended cooling water treatment control parameters

It’s important to stay vigilant and keep the following in mind:

• Operation
• Water treatment
• Preventive and corrective maintenance (documentation)
• Statistical trending of key performance indicators and testing parameters
• Automated system monitoring, control, and communication
• Well-designed and executed calibration program

Many factors contribute to the efficiency of your cooling system. As with all other technologies, due diligence is necessary when determining the feasibility of utilizing new methods. Always consult your equipment manuals and guides, and don’t forget to contact ChemTreat’s experienced team for assistance!