ME331 Thermo II Refrigeration cycle （ME331热II制冷循环）.pdfVIP

Refrigeration cycle Objectives - Know basic of refrigeration - Able to analyze the efficiency of refrigeration system - contents Ideal Vapor-Compression Refrigeration Cycle Actual Vapor-Compression Refrigeration Cycle Cascade refrigeration systems Multistage compression refrigeration systems Refrigeration cycle Refrigeration is the transfer of heat from a lower temperature region to a higher temperature region Refrigeration cycle is the vapor-compression refrigeration cycle, where the refrigerant is vaporized and condenses alternately and is compressed in the vapor phase. Refrigerator and Heat Pump • Cyclic refrigeration device operating between two constant temperature reservoirs. • In the Carnot cycle heat transfers take place at constant temperature. • If our interest is the cooling load, the cycle is called the Carnot refrigerator. • If our interest is the heat load, the cycle is called the Carnot heat pump. (Reversed Carnot cycle) Refrigerator Heat pump • Coefficient of performance, COP Desired output COP= Require input Refrigerator: is used to maintain the refrigerated space at a low temperature by removing heat from it Cooling effect Q COP = L R Work input W , net in Heat pump: heat transfers from a low-temperature medium to a high temperature medium Heating effect