Typically, the refrigerant concentration is chosen to be 5-8°C below the freezing point temperature of the refrigerant. The refrigerant is an intermediate medium used to transfer coldness in indirect refrigeration systems. Cruise ship centralized air conditioning systems and specialized refrigerated ships often use refrigerants to transfer coldness. After the refrigerant cools the refrigerant in the evaporator of the refrigeration system, it is used to cool the cooled material, then returns to the evaporator to transfer heat to the refrigerant. The refrigerant plays a role in carrying coldness, hence also known as the cold medium. Using an indirect refrigeration system allows the refrigeration system to be concentrated in a smaller space, reducing the amount of refrigerant required and the possibility of leaks. Refrigerant flow control can be used to manage and distribute the refrigeration capacity. The drawback is that the system is complex, which increases the temperature difference between the cooled object and the refrigerant.
In indirect refrigeration systems, the transfer of cooling capacity is achieved through refrigerants, which commonly include water, calcium chloride, sodium chloride, and other salt solutions, as well as organic solutions like ethylene glycol and glycerol. There are also numerous formulations kept confidential. To mitigate corrosion of the piping system by the refrigerants, it is common to add corrosion inhibitors and inhibitors to the solution.
Certainly, refrigerants like Freon and carbon dioxide can also be referred to as refrigerants. Compared to aqueous solutions, their differences are quite evident. Aqueous solutions rely on sensible heat without phase change, whereas the refrigerant cycles of Freon or carbon dioxide involve phase changes.
Water has a long history as a refrigerant, widely used in central air conditioning systems or those above 5°C.
Saltwater is suitable for lower temperatures, sodium chloride solutions are appropriate for refrigeration systems with evaporation temperatures above -16℃, and calcium chloride solutions are suitable for systems with evaporation temperatures not below -50℃. When selecting the saltwater concentration, avoid overly high levels; as the specific gravity increases, the power consumption of the pump used to transport the saltwater also rises.
Due to the varying physical properties of solutions with different concentrations, whether it be saltwater or solutions like ethylene glycol used as refrigerants, it is crucial to regularly measure the concentration during operation. Timely adjustments should be made to maintain the solubility of the solution to prevent destructive effects caused by a decrease in concentration and an increase in freezing point.
Ethylene glycol solutions are less corrosive to metals than saltwater and are widely used. Ethylene glycol comes in two types: ethylene glycol and propylene glycol. Since ethylene glycol has a significantly lower viscosity than propylene glycol, it is more commonly used in refrigerants.
