Cooling Tower in Pakistan: Types, Working, Formulas, Equipment, and Efficiency Guide

A cooling tower is an important industrial system used to remove extra heat from water and send cooler water back to machines, chillers, condensers, HVAC systems, power plants, factories, hospitals, malls, textile units, chemical plants, and food industries. In Pakistan, cooling towers are widely used because many cities face high temperatures, dusty air, hard water, and long working hours in industrial areas.

The main purpose of a cooling tower is simple: it cools hot water by bringing it into contact with air. A small part of the water evaporates, and this evaporation removes heat from the remaining water. The cooled water is then reused in the system.

TL; DR - Cooling Towers

A cooling tower cools hot water by using air and evaporation, then sends the cooled water back to industrial machines, chillers, or HVAC systems. In Pakistan, FRP cooling towers are popular because they resist corrosion, handle hard water better, and suit hot industrial environments. Key factors for performance include tower type, fan airflow, approach temperature, evaporation loss, blowdown, chemicals, and regular maintenance.

What Is a Cooling Tower?

A cooling tower is heat rejection equipment. It takes hot water from a process or air-conditioning system and cools it through air movement and evaporation. Instead of wasting water after one use, a cooling tower allows the same water to circulate again and again.

This makes it useful for industries in Pakistan where water saving, power saving, and equipment protection are important.

How Does a Cooling Tower Work?

Inside a cooling tower, hot water enters from the top or side. This water is spread over fill media through nozzles or distribution channels. At the same time, a cooling tower fan pulls or pushes air through the tower.

When air and water meet, some water evaporates. This evaporation takes heat away. The cooled water collects in the basin and returns to the machine, chiller, or process.

In simple words:

Hot water enters → water spreads over fill → air passes through → heat leaves with air → cool water returns.

Function and Purpose of Cooling Tower

The main function of a cooling tower is to reduce water temperature. Its purpose is to keep machines, chillers, and industrial systems safe from overheating.

A good cooling tower helps to:

Reduce heat load
Improve chiller performance
Save water through recirculation
Lower energy cost
Protect equipment life
Support continuous industrial operation

For Pakistan’s textile, plastic, chemical, dairy, hospital, and commercial HVAC sectors, a properly selected cooling tower can reduce breakdowns and improve daily performance.

Types of Cooling Tower

There are many types of cooling tower, but the most common are:

1. Cross Flow Cooling Tower

In a cross flow cooling tower, water flows downward while air moves horizontally across the water. These towers are easy to maintain and often used where inspection access is important.

2. Counter Flow Cooling Tower

In a counter flow cooling tower, water flows downward and air moves upward in the opposite direction. This design is compact and usually offers better heat transfer in limited space.

Difference Between Cross Flow and Counter Flow Cooling Tower

The main difference is air direction. In cross flow, air moves across the falling water. In counter flow, air moves upward against the falling water. Counter flow towers are usually more compact, while cross flow towers are easier to inspect and maintain.

3. FRP Cooling Tower

FRP means fiberglass reinforced plastic. An FRP cooling tower is popular in Pakistan because it resists corrosion better than many metal structures. This is helpful in humid, chemical, and hard water environments.

4. Hybrid Cooling Tower

A hybrid cooling tower combines wet and dry cooling methods. It is used where water saving, lower visible plume, or special environmental needs are important. Hybrid cooling towers are usually selected for advanced industrial and commercial projects.

5. Closed Loop Cooling Tower

In a closed loop system, process water stays inside coils and does not directly mix with outside air. This helps reduce contamination and is useful where clean water circulation is required.

Cooling Tower Equipment and Main Parts

Common cooling tower equipment includes:

Cooling tower fan
Motor
Gearbox or belt drive
Fill media
Water distribution system
Spray nozzles
Drift eliminators
Louvers
Cold water basin
FRP casing or structure
Access ladder and platform
Makeup water system
Blowdown valve
Chemical dosing system

The cooling tower fan is one of the most important parts. It moves air through the tower. If the fan is weak, damaged, wrongly sized, or running at poor speed, cooling performance will drop.

Inside a Cooling Tower

Inside a cooling tower, you normally find fill media, water nozzles, drift eliminators, basin, fan assembly, support structure, and air passage. The fill media increases the contact area between water and air. More contact means better cooling.

Drift eliminators stop water droplets from escaping with air. The basin collects cooled water. The fan controls airflow. All these parts must work together for stable cooling.

Cooling Tower Approach Temperature

Cooling tower approach temperature is the difference between cold water leaving the tower and the ambient wet bulb temperature.

Formula:

Approach = Cold Water Temperature – Wet Bulb Temperature

A lower approach means better performance, but it also needs better design, larger tower size, proper airflow, and clean fill media.

For example, if cold water is 32°C and wet bulb temperature is 27°C, the approach is 5°C.

Cooling Tower Range

Range is the difference between hot water entering and cold water leaving the tower.

Formula:

Range = Hot Water Temperature – Cold Water Temperature

If hot water enters at 40°C and leaves at 32°C, the range is 8°C.

How to Calculate Cooling Tower Efficiency

Cooling tower efficiency can be calculated with this formula:

Efficiency = Range ÷ (Range + Approach) × 100

Example:

Hot water = 40°C
Cold water = 32°C
Wet bulb = 27°C

Range = 40 – 32 = 8°C
Approach = 32 – 27 = 5°C

Efficiency = 8 ÷ (8 + 5) × 100
Efficiency = 61.5%

This gives a practical idea of how close the tower is working to ideal cooling.

Cooling Tower Evaporation Loss Formula

Evaporation loss happens because some water turns into vapor during cooling. This is normal and cannot be fully removed.

A common formula is:

Evaporation Loss = 0.00085 × 1.8 × Circulating Water Flow × Range

Where circulating water flow is in m³/hr and range is in °C.

Example:

Flow = 100 m³/hr
Range = 8°C

Evaporation Loss = 0.00085 × 1.8 × 100 × 8
Evaporation Loss = 1.224 m³/hr

This means around 1.224 cubic meters of water may evaporate every hour.

Cooling Tower Capacity Formula

Cooling tower capacity is usually calculated from water flow and temperature difference.

Basic formula:

Heat Load = Water Flow × Specific Heat × Temperature Difference

In practical HVAC use, capacity is also discussed in TR.

Approximate formula:

TR = Flow Rate in GPM × Range in °F ÷ 24

This helps engineers estimate the cooling load, but final tower selection should be done according to site temperature, wet bulb data, water quality, and process requirement.

What Is Blowdown in Cooling Tower?

Blowdown in cooling tower means removing some concentrated water from the system. When water evaporates, salts and minerals stay behind. Over time, these dissolved solids increase and can cause scaling, corrosion, and poor heat transfer.

Blowdown controls this concentration by draining some water and replacing it with fresh makeup water.

What Is Cycle of Concentration in Cooling Tower?

Cycle of concentration shows how many times water minerals are concentrated compared to makeup water.

Formula:

COC = TDS of Cooling Water ÷ TDS of Makeup Water

Higher COC means better water saving, but too high COC can create scale and corrosion. In Pakistan, water quality changes from city to city, so COC should be managed with proper testing.

What Is Drift Loss in Cooling Tower?

Drift loss is the small amount of water droplets carried away with exhaust air. It is not evaporation. It is actual liquid water escaping from the tower.

Good drift eliminators reduce drift loss. If drift is high, it wastes water, spreads chemicals, and may create safety issues near the tower.

Chemical Used in Cooling Tower

Common chemicals used in cooling towers include:

Scale inhibitors
Corrosion inhibitors
Biocides
Algae control chemicals
pH control chemicals
Dispersants

The exact chemical program depends on makeup water quality, tower material, temperature, dust level, and system use. In Pakistan, hard water and dusty air make chemical treatment very important.

How to Increase Cooling Tower Efficiency

To increase cooling tower efficiency, start with regular cleaning. Dirty fill, blocked nozzles, weak fan airflow, poor water distribution, and scale buildup can reduce performance.

Useful steps include:

Clean fill media and basin
Check fan blade angle
Maintain motor and gearbox
Remove scale and algae
Use correct chemicals
Control blowdown properly
Check water flow rate
Inspect drift eliminators
Keep air inlet area open
Use proper tower size for load

Many cooling problems are not due to bad tower design. They happen because of poor maintenance.

Cooling Tower Manufacturer in Pakistan

When choosing a cooling tower manufacturer in Pakistan, buyers should check material quality, design experience, fan and motor selection, FRP strength, after-sales support, spare parts, warranty, and project history.

FCI Composites is known in Pakistan for FRP cooling tower manufacturing and industrial composite solutions. For Pakistani industries, choosing a local cooling tower manufacturer can make installation, inspection, maintenance, and spare parts easier.

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