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I. Control of moisture content in refrigerants for industrial refrigeration units: For commonly used Freon refrigerants, the moisture content is required to be kept below 25PPm. Freon gases have excellent chemical stability, and generally they do not react directly with water. However, when in contact with metals, it reacts slowly with water. This reaction is known as a hydration reaction; the acid produced in this reaction (such as HCl) reacts with the oil, causing the quality of the lubricant to deteriorate and precipitates to form. Corrosion occurs simultaneously, damaging the insulation of enclosed motors, or copper plating appears on compressor components (that is, on the surfaces of steel exposed to high temperatures), such as on the inner surfaces of cylinders, pistons, connecting rods, crankshafts, and other parts, where a copper-plated-like deposit forms. In severe cases, \"carbon buildup\" can occur, negatively affecting the performance of the machine. Moreover, the refrigerants used in industrial refrigeration systems can corrode metals such as magnesium, magnesium alloys, and aluminum alloys containing more than 1% magnesium – even a small amount of moisture is sufficient to cause corrosion in these metals (except for pure lead). However, with proper drying of the refrigeration systems in industrial refrigerators, copper plating does not occur; therefore, it is necessary to make every effort to avoid the presence of water in the refrigerant or within the refrigeration system. Reasons for moisture entering the refrigeration system: 1. The purity of the refrigerant itself has an excessive water content ； 2. The moisture content in the lubricating oil is above the limit ； 3. During the pressure test of the refrigeration system, if the vacuum level achieved during the vacuum test is not high or if there are leaks in the system, air from outside the system can enter and bring along moisture as well ； 4. During refrigerant charging, improper handling led to air being introduced into the system. II. Measures for dehumidification in the refrigeration systems of industrial refrigeration machines 1. Perform thorough vacuuming before charging the refrigerant; the higher the vacuum level, the better. Vacuum pumping is one of the methods used for dehumidifying and drying systems. The duration of drying in such systems depends on factors such as the size of the system’s containers, the performance and efficiency of the vacuum pump, the indoor temperature, and the amount of moisture present in the system. Generally, when the temperature and pressure of the system reach 1.7°C and 5 mmHg gauge, it can be considered that all the air within the system has been removed. Then, a certain amount of nitrogen is added, and the industrial refrigeration system is evacuated again to reach the aforementioned temperature and pressure; it can be assumed that the system’s requirements regarding dryness and vacuum have been met at the desired level. 2. When charging a industrial refrigeration machine system with refrigerant, external drying of the refrigerant is performed, that is, a dry filter is installed in the filling pipeline; the desiccants used include calcium fluoride, silica gel, molecular sieves (synthetic zeolites), etc. Reduce the water content of the refrigerant entering the system to a certain level. 3. A dry filter should be installed on the pipeline of the high-pressure liquid line in the refrigeration system of industrial refrigerators, prior to it reaching the thermal expansion valve, in order to further remove any water present as well as precipitates that form as a result of chemical reactions during operation. Desiccants typically use 4A0 molecular sieves, whose saturated water absorption rate can reach 21–25% (by mass). To prevent the desiccant powder from causing damage to the system, core-type desiccants are generally used nowadays. When selecting a desiccant filter, the flow velocity inside the cylinder is usually set at 0.03 m/s. For R134a systems, the desiccants used are XH7 (carbide) or 3×10-10 M-type molecular sieves. The reason is that, compared to R12, water has a lower solubility in R134a; therefore, in R134a systems, especially those at low temperatures, desiccants with better water-absorbing capabilities are required. Thus, desiccants commonly used in R12 refrigeration systems are clearly not suitable. III. Components of the refrigeration system in dehumidifying dryers The refrigeration system of dehumidifying dryers consists of an expansion valve, a refrigeration compressor, a water-cooled condenser, a plate evaporator, etc. The main unit of the dehumidifying dryer is equipped with an imported single-unit two-stage semi-hermetic compressor; each main unit forms an independent refrigeration cycle system, cooling the plate layers and the cold trap respectively through plate heat exchangers or condenser tubes. The cold trap of the refrigeration system is a device used to capture sublimated water vapor; it is integrated with the drying oven, separated from it by a mushroom valve/butterfly valve, allowing material intake and output as well as defrosting to take place simultaneously. After entering the freeze-drying completion determination procedure, a pressure test is automatically performed to identify the end point of freeze-drying. In the event of a short power outage (10 minutes), to protect the products, a small butterfly valve will close automatically, utilizing the pressure difference between the cold trap and the drying oven to maintain the sublimation state. The system is also equipped with various functions such as motor overload thermal protection, high-pressure protection, low-pressure protection, medium-pressure protection, oil pressure difference protection, automatic liquid collection, and cooling water shortage protection. The compressor is also equipped with a CPCE pressure regulator to prevent it from operating under extreme conditions, thereby balancing the secondary compression ratio. The refrigeration system is designed with sufficient cooling capacity to handle the water vapor load generated by sublimation.