open
There are two types of cooling equipment, cooling pool and cooling tower, both of which mainly rely on water evaporation to reduce water temperature. Furthermore, cooling towers often use fans to promote evaporation, and cooling water is often blown away. Therefore, the open circulating cooling water system (Figure 1) must be supplied with fresh water. Due to evaporation, circulating water is concentrated, and the concentration process will promote salt scaling (see Sediment Control). The make-up water has a diluting effect, and its flow is often determined according to the circulating water concentration limit. Usually the amount of supplemental water exceeds the loss of evaporation and wind, so some circulating water (called sewage) must be discharged to maintain the balance of water. Circulating cooling water system
In the open system, dust and microorganisms enter the circulating water due to the contact of the water flow with the atmosphere; in addition, the escape of carbon dioxide and the leakage of materials in the heat exchange equipment; also change the water quality of the circulating water. For this reason, circulating cooling water often needs to be treated, including sediment control, corrosion control and microbial control. The determination of the treatment method is often related to the amount and quality of the make-up water, as well as the performance of the production equipment. When using multiple agents, avoid possible chemical reactions between the agents.
Closed
The closed circulating cooling water system (Figure 2) uses closed cooling equipment. The circulating water flows in the pipe, and the outside of the pipe is usually cooled by wind. Except for the material leakage of heat exchange equipment, no other factors change the quality of circulating water. In order to prevent salt scale in the heat exchange equipment, sometimes the cooling water needs to be softened (see water softening). In order to prevent the heat exchange equipment from being corroded, corrosion inhibitors are often added; when using high-concentration, highly toxic corrosion inhibitors, pay attention to safety, and the cooling water discharged during maintenance should be properly disposed of.
