Cooling Water Circulation System

A recirculating cooling water system is a water supply system that cools water by transferring heat, then lowers its temperature before reusing it. This system comes in two main types: open and closed. Primarily, it consists of cooling equipment, pumps, and piping. When cold water flows through production equipment requiring cooling (commonly referred to as heat-exchanging devices, such as heat exchangers, condensers, or reactors), its temperature rises. If this water were immediately discharged afterward, it would only be used once—this is known as a once-through cooling water system.

By passing warm cooling water through the cooling equipment, the water temperature drops. Apart from any material leaks from the heat-exchange devices, the cooled water can be pumped back into production equipment for reuse. Typically, heat is dissipated from the outside of the pipes using ambient air. This approach significantly reduces the volume of cold water required—often resulting in savings of more than 95%. Since cooling water accounts for approximately 70% of industrial water consumption, circulating cooling water systems play a crucial role in conserving vast amounts of industrial water.

Principle

A cooling water system that uses water as the coolant medium and recirculates it. It primarily consists of cooling equipment, a water pump, and a piping network. After cold water flows through production equipment requiring temperature reduction (commonly referred to as heat exchange equipment, such as heat exchangers, condensers, or reactors), its temperature rises. If this water were discharged immediately afterward, it would only be used once—this is known as a once-through cooling water system.

Passing warm cooling water through cooling equipment lowers its temperature, allowing it to be pumped back into production systems for reuse. This significantly reduces the amount of cold water needed—often resulting in savings of more than 95%. Since cooling water accounts for approximately 70% of industrial water usage, circulating cooling water systems play a crucial role in conserving vast amounts of industrial water.

Category

Cooling equipment is categorized into open and closed types, and accordingly, circulating cooling water systems are also divided into two categories: open and closed. The design and operation of open systems, however, are relatively more complex.

 Open-loop cooling systems feature two main types of equipment: cooling ponds and cooling towers, both of which rely primarily on water evaporation to reduce water temperature. Additionally, cooling towers often use fans to enhance evaporation, leading to significant water loss through drift. Thus, open-loop circulating cooling water systems…

Fresh water must be replenished. Due to evaporation, the circulating water becomes concentrated, and this concentration process can promote salt scaling (see sediment control). Adding fresh water helps dilute the system, and its flow rate is typically determined based on the concentration limits of the circulating water. Usually, the amount of makeup water exceeds the losses from evaporation and windage, which is why some of the circulating water must be discharged (known as blowdown) to maintain water balance. Closed-loop cooling water systems: In open systems, as the water flows in contact with the atmosphere, contaminants such as dust and microorganisms enter the circulating water. Additionally, carbon dioxide may escape, and leaks from heat-exchanging equipment can introduce unwanted materials, all of which alter the water quality. For these reasons, circulating cooling water often requires treatment—including sediment control, corrosion inhibition, and microbial management. The choice of treatment methods usually depends on both the quantity and quality of the makeup water, as well as the performance characteristics of the equipment being used. When multiple chemicals are employed, care must be taken to avoid potential chemical reactions between them.

Closed-loop circulating cooling water system

Closed-loop cooling systems are used, where circulating water flows through pipes, and heat is typically dissipated by air cooling on the pipe exterior. Apart from potential material leaks from the heat-exchange equipment, no other factors affect the quality of the circulating water. To prevent salt deposits from forming inside the heat exchangers, the cooling water sometimes needs to be softened (see "Water Softening"). Additionally, corrosion inhibitors are often added to protect the heat-exchange equipment from corrosion. When using highly concentrated, highly toxic corrosion inhibitors, safety precautions must be strictly observed, and any cooling water discharged during maintenance should be properly handled. The cooling circulation system consists of components that monitor the flow rate of the medium in the pipeline. If the flow rate drops too low or rises too high due to blockages or other issues within the pipeline, the system promptly sends a discrete signal—either a low-flow alarm (when flow is insufficient) or a high-flow alarm (when flow exceeds the safe range)—to the control system. This device is known as the Flow Alarm Switch.