There are two cooling methods for refrigeration equipment: direct cooling and indirect cooling. Direct cooling is to install the evaporator of the refrigerator in the box or building of the refrigeration device, use the evaporation of the refrigerant to directly cool the air, and cool the objects that need to be cooled by cold air. The advantages of this cooling method are fast cooling speed, small heat transfer temperature difference, and relatively simple system, so it is widely used. Refrigeration equipment is a device that combines a refrigerator with a facility that uses cooling capacity. The design and construction of refrigeration equipment are to effectively use the cooling capacity to refrigerate food or other items; to conduct product performance tests and scientific research tests at low temperatures; to achieve certain cooling processes in industrial production, or to perform air conditioning.
When cooling or freezing items, a certain amount of heat should be released, and the enclosure structure of the refrigeration device will also transfer a certain amount of heat when it is used. Therefore, in order to maintain the low-temperature conditions in the refrigeration device, it is necessary to install a refrigerator in order to continuously remove this heat, or use the melting of ice or the sublimation of dry ice to absorb this heat.
Before artificial refrigeration began to develop, humans had known to use natural ice and snow to maintain low-temperature conditions in simple equipment, that is, to use natural cold sources. In China, natural ice was used to preserve food about 3000 years ago, and there are poems about collecting, storing and refrigerating food with natural ice in the Book of Songs in the seventh century BC. Until modern times, people still use natural cold sources such as ice, snow, and groundwater.
Refrigerators cooled with natural or artificial ice can only reach a limited low temperature, and the technical and hygienic conditions are poor, making it difficult to meet many requirements. Modern refrigeration devices are cooled by refrigerating machines.
The above information is provided by cold storage manufacturers.