Closed Circuit Cooling Tower Sequence of Operation

A closed circuit cooling tower is a type of heat rejection system that combines the principles of air and water cooling. It is often used to cool fluids in industrial processes, HVAC systems, or power plants. In a closed cooling tower, water flows in a closed loop, and heat is transferred from the water to the air, which is then expelled from the tower. The sequence of operation describes how the system works to ensure efficient heat transfer and cooling. Here's a general sequence:

1. Start-Up Process

System Initialization:

The cooling system (e.g., pump, fans, etc.) is powered on.

The primary pump starts circulating the fluid (usually water) through the closed-loop circuit.

Water Circulation:

Water from the process is pumped into the cooling tower heat exchanger (usually a coil or finned-tube system). This water is typically pre-heated from the industrial process.

2. Heat Transfer to Heat Exchanger

Heat Exchanger:

The warm water from the process enters the cooling tower's heat exchanger or coil system.

As water flows through the coil system, ambient air is blown across the coils, absorbing the heat from the water inside the coil.

The water in the closed loop remains isolated from the environment to avoid contamination or mineral buildup, while the air absorbs the heat.

3. Airflow & Evaporation

Fans or Air Movement:

Fans at the top of the cooling tower are activated to pull or push ambient air across the heat exchanger or coil system.

This process increases heat transfer by both convective cooling (air flow) and a minimal amount of evaporative cooling (if the system is designed to do so).

Heat Rejection:

Heat is transferred from the water in the coils to the surrounding air, which leaves the tower through vents or louvers.

The temperature of the water drops as it flows through the cooling tower, and cool water is returned to the system or process.

4. Water Return & Recirculation

Return to Process:

The cooled water is returned to the industrial process, cooling the fluid back down to the required temperature.

This water is now ready to absorb heat again from the process or equipment that needs cooling.

Water Make-Up:

Any water lost due to evaporation or drift is replaced with make-up water, typically from a municipal supply or a nearby water source.

This ensures that the system maintains the proper level of water to operate efficiently.