Cooling Tower System: Working Principle, CHWP and CWP Explained
Electrical Kelas Teknisi | In a building cooling system that uses a water-cooled chiller, the cooling tower plays a critical role. Its main function is to reject heat from the cooling system into the ambient air, allowing the chiller to operate efficiently and reliably.
This article provides a complete and practical explanation of what a cooling tower is, how it works, its relationship with CHWP and CWP pumps, and the key water quality parameters that must be maintained for optimal operation.
What Is a Cooling Tower?
A cooling tower is a heat rejection device designed to remove excess heat from a cooling system and release it into the atmosphere. In a water-cooled chiller system, heat absorbed from the building by chilled water is transferred to the chiller condenser and finally discharged through the cooling tower.
Simply put, a cooling tower works like a radiator for a chiller system. Without a cooling tower, heat cannot be released effectively, causing the chiller to lose efficiency and increasing energy consumption.
Relationship Between Cooling Tower, CHWP, and CWP
In a centralized building cooling system, two main pumps operate together with the cooling tower: CHWP (Chilled Water Pump) and CWP (Condenser Water Pump).
Function of CHWP (Chilled Water Pump)
The CHWP circulates chilled water from the chiller to the building, supplying AHUs or FCUs to cool indoor spaces. After absorbing heat from the rooms, the water returns to the chiller at a higher temperature.
Function of CWP (Condenser Water Pump)
The CWP pumps hot condenser water from the chiller to the cooling tower. Inside the cooling tower, this water is cooled before being sent back to the chiller condenser.
In short, CHWP handles cold water distribution inside the building, while CWP manages heat rejection through the cooling tower. Both pumps are equally important to ensure stable and efficient HVAC system performance.
How a Cooling Tower Works
Cooling towers operate based on the principle of evaporative cooling. Hot condenser water, typically at a temperature of 32–35°C, is pumped into the cooling tower.
Inside the tower, water is sprayed through nozzles and distributed over fill media. A fan located at the top draws ambient air through the falling water.
When hot water comes into contact with airflow, a small portion of the water evaporates. This evaporation absorbs heat, reducing the water temperature. The cooled water exits the cooling tower at around 26–30°C and returns to the chiller condenser.
This cycle continues continuously as long as the building cooling system is operating.
Cooling Tower Water Parameters That Must Be Controlled
To ensure reliable performance and prevent equipment damage, cooling tower water quality must be properly controlled. Key parameters include:
1. Water Temperature
The ideal cooling tower outlet water temperature is 26–28°C. Higher temperatures will reduce chiller efficiency and increase energy consumption.
2. Water pH
The recommended pH range is 6.5 to 8.5. Low pH can cause corrosion, while high pH increases the risk of scale formation.
3. TDS (Total Dissolved Solids)
TDS indicates the concentration of dissolved minerals in the water. It is commonly maintained below 1500 ppm, depending on building standards and water treatment policies.
4. Blowdown
Blowdown is the controlled discharge of a portion of cooling tower water containing high TDS and contaminants. This process helps maintain stable water quality and protects system components.
Conclusion
The cooling tower is a vital component of a water-cooled chiller system. By understanding how it works, its relationship with CHWP and CWP, and by maintaining proper water parameters such as temperature, pH, TDS, and blowdown, building cooling systems can operate more efficiently, last longer, and reduce operational costs.
Cooling Tower FAQ
What is the main function of a cooling tower?
The main function of a cooling tower is to remove heat from the cooling system and release it into the atmosphere so the chiller can operate efficiently.
What is the difference between CHWP and CWP?
CHWP circulates chilled water to cool indoor spaces, while CWP circulates hot condenser water from the chiller to the cooling tower.
What is the ideal cooling tower outlet water temperature?
The ideal outlet water temperature ranges from 26 to 28 degrees Celsius.
Why is blowdown necessary in a cooling tower?
Blowdown is required to reduce TDS and contaminants in the water, preventing scaling, corrosion, and efficiency loss.
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