When selecting screw chillers or large-scale chiller units, users typically carefully verify the cooling capacity and compressor specifications; however, the critical factor of the circulating fluid medium is often overlooked. As the heat transfer medium for refrigeration chillers, if the fluid medium does not match the operating conditions—even when all hardware parameters meet the requirements—this can lead to a series of production incidents, such as pipe freezing and blockage, reduced heat transfer efficiency, or equipment alarms triggering shutdowns.

For process scenarios with outlet water temperature above 5℃, such as coating chiller and conventional industrial cooling, it is recommended to use soft water or deionized water. In an air-cooled chiller project of a coating processing plant, tap water was directly filled for production at the initial stage. In just three months, a large amount of scale accumulated in the pipelines, and the filter was frequently blocked. Abnormal flow caused temperature fluctuations in the coating chamber, and the product yield decreased significantly. The equipment returned to stability only after replacing the soft water and installing anti-scaling components. Tap water is rich in minerals, and long-term circulation is prone to scaling and corrosion of the heat exchanger, which is not suitable for the continuous operation of industrial equipment.

When the process outlet water temperature drops below 5℃, such as in chemical chiller and ultra-low temperature chiller operating conditions, clean water can no longer meet the requirements, and ethylene glycol coolant must be mixed. A chemical customer who purchased an ultra-low temperature screw unit did not add ethylene glycol to save costs, and directly set the clean water outlet temperature to -8℃. The pipeline quickly froze and cracked the heat exchanger, causing tens of thousands of yuan in equipment damage, and the entire production line was shut down for emergency repair. The proportion of ethylene glycol should be determined according to the minimum process temperature; if the proportion does not meet the standard, pipe freezing will still occur.

The selection of media must also comply with industry-specific requirements. For food and pharmaceutical processes, propylene glycol is preferred to avoid the toxicity associated with ethylene glycol; for general industrial cooling applications, ethylene glycol is used to balance cost considerations with anti-freezing performance; when handling corrosive materials, it is essential to verify the compatibility of the fluid with the heat exchanger tubing to prevent corrosion of internal components.

For the same large-scale chiller unit, the heat transfer efficiency will change after the fluid is replaced. An increase in the viscosity of high-concentration ethylene glycol reduces the heat transfer performance; therefore, during the equipment selection phase, the manufacturer should perform a cooling capacity adjustment rather than directly applying the operating parameters for pure water conditions.

Selection Principle: For ambient-temperature applications, prioritize water softening; when temperatures drop below 5°C, ensure the use of an appropriate anti-freezing fluid with the correct concentration; for specialized industries, verify the toxicity of the fluid and the corrosion resistance of the piping system. For the stable operation of screw chillers and air-cooled chillers, both the hardware and the fluid are essential – selecting the correct fluid is key to preventing unnecessary downtime.

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