Closed Cooling Towers: An Overview and Operational Guide

Closed cooling towers, also known as evaporative air coolers, are innovative heat exchange systems that incorporate a tubular heat exchanger within the tower structure. These towers facilitate cooling by circulating air and spraying water externally around the tubes while circulating water flows internally through them. The closed-loop design ensures that the circulating water remains uncontaminated, thereby preserving water quality and safeguarding the efficient operation of primary equipment while extending its service life. Additionally, when external temperatures are low, the spray water system can be deactivated to conserve water. With the increasing emphasis on energy conservation and emission reduction, coupled with growing water scarcity, closed cooling towers have gained widespread adoption across various industries, including iron and steel metallurgy, power electronics, mechanical processing, and air conditioning systems.

1. Classification of Closed Cooling Towers

Closed cooling towers can be categorized based on several criteria:

• Flow and Wind Direction: They can be classified as counterflow, cross-flow, or mixed-flow closed cooling towers, depending on the direction of air and water flow relative to each other.

• Shell Material: Based on the material used for the outer shell, closed cooling towers can be divided into galvanized steel, aluminum-zinc plate, stainless steel, and glass fiber reinforced plastic types.

• Heat Exchanger Material: The materials used for the heat exchanger tubes include copper, stainless steel, carbon steel, titanium, and aluminum, leading to corresponding classifications of closed cooling towers.

• Fan Type: Closed cooling towers can also be differentiated by the type of fan used, namely draft type and blast type.

2. Operational Steps for Closed Cooling Tower Control

2.1 Initial Startup

1. Confirm Connections: Ensure that all corresponding pipelines and control lines are properly connected.
2. Activate Equipment: Press the "Main Water Pump On" and "Fan On" buttons (indicated by illuminated lights). Observe the following:
   • The water pump should rotate clockwise, with water flowing in the direction indicated by the arrows.
   • Check for normal water pressure, leaks, and abnormal sounds.
   • Verify that the fan's airflow is directed upwards. If not, swap two of the three wires of the fan motor in the electric control cabinet.
   • Address any abnormal vibrations immediately; if unresolved, contact the company promptly.

2.2 Sprinkler System Operation

The sprinkler system operates on an automatic temperature control mechanism:

• Upon starting the sprinkler switch, the sprinkler pump will automatically start and stop in response to temperature fluctuations.
• The automatic temperature controller's parameters are typically preset at the factory and should not be altered arbitrarily to prevent control failures.
• If temperature parameter adjustments are necessary, technical personnel should carefully read the instructions or seek guidance from professional technicians before making changes.

2.3 Shutdown Procedures

1. General Equipment Shutdown: To stop the general equipment, press the "Water Pump Stop" and "Fan Stop" buttons. The entire device will cease operation.
2. Cooling for Furnaces: If the cooling equipment serves a diathermic or melting furnace, do not stop the cooling system immediately after the furnace stops. Wait until the furnace has completely cooled before shutting down.
   • A time relay is incorporated into the cooling system for such scenarios. In case of a power outage, adjust the time relay to the desired duration, turn on the time relay button, and turn off the fan. Upon restarting, turn off the time relay switch, and the water pump will automatically resume operation, protecting the equipment and conserving energy.
   • Warning: Never run the pump without water!

2.4 Resetting Thermal Overload Protection

• Thermal overload relays for both the fan motor and pump motor are installed in the electrical system.
• After a protection action occurs, press the red reset button on the thermal overload relay at the lower end of the corresponding AC contactor to reset it.
• Failure to reset will prevent the "Pump On" or "Fan On" buttons from activating the corresponding AC contactor.

2.5 Water Tank Replenishment

• Monitor the liquid level display pipe on the closed cooling tower's water tank.
• If the water level drops below two-thirds of the tank's capacity, promptly add soft water to replenish it.

By following these operational guidelines, users can ensure the efficient and safe operation of closed cooling towers, maximizing their benefits across various industrial applications.

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