The refrigeration method is divided into vapor compression refrigeration, absorption refrigeration, steam injection refrigeration, gas expansion refrigeration, and thermoelectric refrigeration. Among the above refrigeration methods, vapor compression refrigeration is the most economical and widely used refrigeration method, and it is also the most commonly used refrigeration method in environmental test equipment. The principle is to absorb heat from the cooled object by using the latent heat of evaporation of liquids such as Freon. And achieve refrigeration. (Single-stage refrigeration cycle diagram) is a schematic diagram of a vapor compression refrigeration cycle process. The liquid that enters the evaporator through the expansion valve absorbs the latent heat of evaporation from the surrounding objects and evaporates. After evaporation, it becomes a low-temperature low-pressure gas and is sucked by the refrigeration compressor. After being compressed by the compressor, it becomes a high-temperature high-pressure gas and enters the water-cooled or air-cooled condensation. The device is cooled to a high pressure liquid and then enters the evaporator through an expansion valve. In such a reciprocating cycle, the heat is absorbed from the low temperature to achieve cooling, and then the heat is released from the high temperature. In a refrigeration cycle (single-stage refrigeration cycle diagram), a change from one state to another is called a process. There are four processes in the refrigeration cycle. The following four steps in the refrigeration cycle are briefly described. (1). Evaporation process: The low-pressure wet steam after expansion and throttling absorbs heat from the surrounding medium in the evaporator and gradually increases its dryness. Thus, the gas coming out of the evaporator has become a dry saturated vapor or a slightly superheated superheated vapor. The refrigerant temperature and pressure remain constant during the evaporation process. (2). Compression process: After the refrigeration is completed, the vapor from the evaporator enters the refrigerator. After compression, the temperature and pressure rise sharply. Therefore, the gas discharged from the refrigerator becomes a hot steam with a high degree of superheat. During the compression process, the refrigerant entropy value does not change. (3). Condensation process: The high-temperature and high-pressure superheated steam discharged from the refrigerator enters the condenser and exchanges heat with the cooling water or air, so that the superheated steam gradually becomes saturated vapor and becomes a saturated liquid. When cooled with cooling water, the temperature of the saturated liquid will continue to decrease and it will be too cold. The pressure remains constant during the condensation process. (4). Throttling process: The liquid coming out of the condenser is throttled by a throttling device such as an expansion valve or a capillary tube, and becomes a low-temperature low-pressure wet steam, and the refrigerant enthalpy value does not change during the throttling process. The above four cycles are continuously cycled in order to achieve the purpose of refrigeration. In order to complete the various thermodynamic processes of the refrigeration cycle, it is necessary to form a system of compressors, heat exchangers, pipelines, pipelines, etc., which is called a refrigeration system. Single-stage compression refrigeration means that the refrigerant vapor is compressed only once, and its minimum evaporation temperature can be controlled at -30 ° C ~ -40 ° C. DELIN HAIR COSMETICS , https://www.hairdyecolorfactory.com
What is a single-stage refrigeration cycle?