Study On Heat Absorbing And Vaporization Characteristics Of Lithium Bromide Solution In Evacuated Collector Tubes

Energy saving and environmental protection is still the focus of social issues at present. Increasing the investment of renewable energy is one of the most important strategies of national development, so the heat utilization of solar energy faces a new development opportunities. Among them, the solar lithium bromide absorption refrigeration is a popular and advanced technology because of its energy saving, environmental friendly, taking advantage of low grade heat source, and it is also a key research point at home and abroad.The complexity of unit and the high initial investment are still the main obstacles to popularize the application of solar lithium bromide absorption refrigeration technology. It can reduce the intermediate heat transfer, simplify the system and improve efficiency to integrate vacuum tube collector and lithium bromide solution generator. At present, the research has not yet commenced with the integrate vacuum tube collector and lithium bromide solution generator. In the paper, experimental studies about heat absorption and evaporation process of the lithium bromide solution have been done in the vacuum tube, and the relevant parameters including solution temperature and evaporation quantity were achieved about lithium bromide solution under typical weather conditions in the vacuum tube for the integration of vacuum tube collector and lithium bromide solution generator. The strengthening measures and effect were discussed and it was proved to be the foundation of the following research. The paper structure arrangement is as follows:Firstly, the theory of heat transfer process of vacuum tube was analyzed and the heat transfer equation of the collector was obtained. The heat loss about different parts of the collector was then analyzed and the calculation formula of the collector efficiency and instantaneous efficiency curve were achieved. Secondly, In the case of receiving solar radiation, the best heat concentration of the lithium bromide solution was achieved through experimental studies on the lithium bromide solution when its mass concentration were 35%, 40%,45% 50%,55%,60% respectively, and the experimental results showed that the best concentration of the lithium bromide solution was 50%. Thirdly, the performances of heat absorption and evaporation of lithium bromide solution of 50% concentration were studied in the vacuum tube, the effects of heat reinforcing measure were explored, and the result showed that the evaporation of single vacuum tube can be converted into the refrigerating capacity up to 8.9W～21.1W and the instantaneous collector efficiency can be up to 17.7%～39.0%. Finally, the vaporization characteristics of Lithium bromide solution are studied in the vacuum tube under the condition of circulation, and the result showed that the evaporation of single vacuum tube under the condition of circulation can be converted into the refrigerating capacity up to 3.9W～12.0W and the instantaneous collector efficiency can be up to 7.5%～16.0%. In addition, the circulation of the solution requires a certain starting time and the starting temperature.