Problems caused by the operation of open circulating cooling water system

(1) Bacterial and Microbial Reproduction

(2) Scale Formation in Water Circulation Systems

(3) Economic Losses Due to Poor Water Quality

I. Bacterial and Microorganism Reproduction

Natural sunlight and nutrients in water facilitate the rapid growth of bacteria, algae, and fungi. Without effective control, microorganisms continuously proliferate and secrete large amounts of mucus, which binds insoluble impurities in the water together. This produces slime that adheres to the internal surfaces of equipment and pipes, impeding water flow and system heat exchange. Furthermore, areas where this sludge accumulates often experience under-deposit corrosion.

II. Scale Formation in Water Circulation Systems

During the heat exchange process between circulating water and heat exchangers, calcium bicarbonate in the water converts to calcium carbonate, carbon dioxide, and water due to heating. These components splash and adhere to the cooling tower and pipes, forming scale in the water circulation system. Water in the cooling tower continuously evaporates, increasing the concentration of dissolved substances. When the concentration exceeds water’s saturation solubility, ions (calcium carbonate) precipitate out, accelerating scale formation in the water circulation system. Once scale forms, it reduces heat exchange efficiency and increases water flow resistance, forcing the compressor to output more power to achieve its original intended effect, resulting in various cost losses:

2) Increased operational costs;

3) Waste of water resources;

4) Greater equipment wear and tear, leading to shortened equipment service life.

III. Economic Losses Caused by Poor Water Quality to the System

1) Energy consumption caused by scale formation.

According to the research data report on scale formation by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE) as follows:

2) Energy Consumption Due to Increased Approach Temperature

According to general principles of water-cooled units: When scale forms on the condenser’s heat exchange surface, it reduces the unit’s cooling efficiency, leading to increased motor load and rising condenser approach temperature (small temperature difference). According to international refrigeration industry research on approach temperature, for every 1-degree rise in approach temperature, energy consumption increases by approximately 2.5%. This has been verified by data obtained after treating the central air conditioning system at Guangzhou Baiyun International Airport Terminal by the Airport Equipment Company of Baiyun Airport.

3) Thermal Resistance Impact of Biofilm and Bacteria

The heat exchange losses caused by biofilm and bacteria are even greater than those caused by inorganic scale. According to a report by the American Cooling Technology Institute (CTI), in terms of thermal resistance, biofilm and bacteria create approximately 5 times more resistance than scale formation.

IV.Comprehensive Conclusion

Given the impacts and losses caused by poor water quality mentioned above, it is essential to perform scale removal and regular water quality stabilization treatment on central air conditioning circulation systems. This is necessary to prevent scale formation, inhibit microorganism growth and reproduction, control equipment and pipeline corrosion, improve heat exchange efficiency, conserve energy, and extend equipment service life. These measures will reduce equipment and pipeline corrosion, control scale formation, suppress microbial proliferation, and ensure that the central air conditioning system operates at the main unit’s set parameters over the long term.

Problems caused by the operation of open circulating cooling water system