Application of Closed-Circuit cooling Tower
Closed-Circuit Cooling Towers (CCT), also known as Fluid Coolers or Evaporative Coolers.
How a Closed-Circuit Cooling Tower Works
First, it’s crucial to understand the fundamental difference:
- An Open Cooling Tower exposes the process water being cooled directly to the atmosphere and recirculates it.
- A Closed-Circuit Cooling Tower has two separate fluid circuits:
- A Closed Loop: The process fluid (water or a water-glycol mix) flows through a coil, never exposed to the atmosphere.
- An Open Loop: A separate spray water system pumps water over the outside of the coil to evaporatively cool it.
The heat from the internal process fluid is transferred through the coil wall to the spray water, which is then cooled primarily by evaporation. This design is the key to its wide range of applications.
Key Applications of Closed-Circuit Cooling Towers
CCTs are chosen where protecting the process fluid from contamination, maintaining a specific fluid quality, or operating in harsh environments is a priority.
1. HVAC and Building Cooling
This is one of the most common applications, especially in commercial and large institutional buildings.
- Chiller Condenser Water Cooling: They are used to cool the condenser water loop for water-cooled chillers that provide air conditioning. They protect the expensive chiller’s heat exchanger from scale, corrosion, and biological fouling that can occur with open towers, leading to higher efficiency and lower maintenance.
- Water-Source Heat Pump Systems: In large buildings with a centralized water-loop heat pump system, the CCT rejects the collective heat from all the individual heat pump units.
- Data Centres: Critical for cooling high-density computing facilities. CCTs prevent airborne contaminants from clogging the sensitive heat exchangers on computer room air handlers (CRAHs) or directly on servers, ensuring reliability and uptime.
2. Industrial Processes
This is a vast category where process integrity is paramount.
- Chemical and Petrochemical Plants: Used to cool reactor jackets, condensers, lubricants, and hydraulic systems. They prevent process contamination and the risk of forming scale or algae inside delicate and critical equipment.
- Food and Beverage Industry: Essential for hygienic cooling applications, such as cooling milk in a dairy, pasteurization processes, or cooling fermentation tanks in a brewery. The closed loop ensures no biological or particulate contamination enters the process stream.
- Pharmaceutical and Medical Manufacturing: Requires extremely pure water (WFI – Water for Injection, purified water). A CCT cools this water without exposing it to airborne pathogens, algae, or minerals, which is a strict regulatory requirement.
- Plastics and Injection Moulding: Used to cool the hydraulic oil and moulds. Consistent, clean cooling is vital for product quality and cycle times. Contaminants in an open system could damage sensitive hydraulic components.
- Power Generation: Cooling lubricating oil for turbines, generators, and transformers. They are also used in auxiliary cooling loops within power plants.
3. Freeze Protection and Year-Round Operation
- Glycol Cooling Loops: The closed loop can be filled with a water-glycol mixture (e.g., 40% glycol, 60% water) to prevent freezing in cold climates. This allows the system to operate year-round without the risk of the process fluid freezing and bursting pipes, which is a major risk with open towers.
4. Water Conservation and Treatment
- Scarce or Expensive Water: In areas with water shortages or high water costs, CCTs are advantageous. Since the process fluid is in a closed loop, the only water loss is from evaporation in the spray circuit, which is similar to an open tower. However, the make-up water required is often of lower quality (and cheaper to treat) because it only contacts the outside of the coil, not the sensitive process equipment.
- Expensive Process Water Treatment: If the process water requires expensive treatment chemicals (e.g., high-purity deionized water), a CCT drastically reduces the volume of water that needs this treatment. You only treat the small, closed loop, not the large, continuously replenished volume of an open system.
. Protecting Expensive and Sensitive Equipment
- Lasers and Medical Equipment: High-power industrial lasers (e.g., for cutting and welding) and medical imaging equipment (e.g., MRI machines) require precise, clean cooling. Any scale or debris can cause catastrophic failure and expensive downtime.
- Hydraulic and Lubrication Systems: Modern hydraulic systems have very tight tolerances. CCTs keep the cooling water clean, preventing clogging and damage to coolers and other components.