Among the various methods of utilizing solar energy for cooling, the solar lithium bromide absorption refrigerator has higher cooling efficiency and can operate at a lower heat source temperature. It is one of the most successful ways to apply solar energy cooling.
The solar lithium bromide absorption refrigeration system consists of solar collectors, generators, condensers, throttle valves, evaporators, solution heat exchangers, absorbers, and pumps. The cycle process is a process of heat and mass exchange. The refrigerant vapor is evaporated in the generator, the lithium bromide solution changes from thin to concentrate, the refrigerant vapor is absorbed in the absorber, the lithium bromide solution changes from thick to thin, and the refrigerant in the evaporator Water vaporizes and absorbs heat at low pressure to achieve the purpose of refrigeration.
At present, solar lithium bromide absorption refrigerators mainly include single-effect, double-effect, triple-effect, and other composite refrigeration cycles. The most widely used in the market is the double-effect unit.
1. Solar-powered single-effect lithium bromide absorption chiller
The single-effect lithium bromide absorption chiller is the simplest type of absorption chiller. The optimum working temperature is 80 to 100 °C. Its maximum COP (coefficient of performance, equal to the cold/heat and refrigeration/ The ratio of thermal system input power) value can reach 0.7 when the heat source temperature is 85 ℃. Since the solution is limited by crystallization conditions, the temperature of the heat source of the refrigerator cannot exceed 150 °C. The energy consumption of the single-effect lithium bromide absorption refrigerator is much higher than that of the traditional compression refrigerator, but its advantage is that it can make full use of low-grade energy as the driving energy, and the low-temperature solar collector is used to produce the same cooling capacity. The hot water can just be used to drive the single-effect absorption refrigerator, which can save electricity and energy, which is unmatched by the compression refrigerator.
2. Solar double-effect and triple-effect lithium bromide suction refrigerator
The heat source temperature of the single-effect absorption chiller is limited by the crystallization of concentrated solution. To make full use of the high-temperature heat source, double-effect, and triple-effect absorption chillers emerge as the times require. Compared with the single effect, the double-effect absorption refrigerator has one more high-pressure generator, one high-temperature solution heat exchanger, and one condensate heat exchanger.
It works as follows: In a high-pressure generator, a dilute solution is heated by high-pressure steam, which produces refrigerant vapor at a higher pressure. The dilute solution was concentrated in an intermediate solution. Then pass this part of the steam into the low-pressure generator as a heat source, heat the high-pressure generator to flow to the intermediate solution in the low-pressure generator through the high-temperature solution heat exchanger, make it generate refrigerant vapor again under the condensing pressure, and concentrate the intermediate solution into a concentrated solution. solution. The energy of the high-pressure steam is utilized twice in the high-pressure generator and the low-pressure generator, so it is called a double-effect cycle.
According to the above principle, expansion is the three-effect cycle. Due to the use of a high-temperature heat source, the COP value of the double-effect absorption refrigerator can reach 1.0 to 1.2, and the three-effect can reach 1.7, which is significantly higher than the single-effect COP value.
With the development of science and technology and the rise of green buildings, solar refrigeration and air-conditioning technology will be greatly improved and improved, and the cost will be greatly reduced. It is believed that solar lithium bromide absorption refrigeration and air-conditioning will have greater development prospects.