A Study On Heat Absorbing And Vaporization Performance Of Lithium Bromide Solution In Parabolic Trough Collector

Environmentally friendly society is a social form in which people and nature coexist harmoniously.It’s one of the crucial part of our nation-building as well.Solar energy,as one of the clean energy that can be used by human beings,has been widely concerned over the world.At the meantime,the field of solar thermal utilization has met a brand new development opportunity.Among them,as a hot spot in the field of solar thermal utilization,solar powered lithium bromide absorption refrigeration technology has been the focus of researchers domestic and overseas with its advantages of environmental friendliness,safety and stability,energy conservation and emission reduction.The current solar powered lithium bromide absorption refrigeration technology still has the problems of complex system,heavy maintenance work and high initial investment,resulting in its slow commercial application.But these problems can be effectively solved by simplifying the equipment.One of the feasible methods to simplified equipment is to couple the storage tank with solution regenerator.At the same time,it has the functions of solar energy collection and heat absorption as well as solution regeneration and storage.In this way,the system can be simplified and heat transfer can be enhanced,and the refrigeration efficiency of the system can be improved,too.In order to research the new type solar solution regenerator,the regeneration device and its experimental test system of lithium bromide solution with parabolic trough collector were built,and the heat absorption and vaporization properties of lithium bromide solution were studied.The main content of this paper includes:(1)Heat transfer analysis of lithium bromide solution in parabolic trough collector.The heat transfer process between lithium bromide solution and metal absorption tube,between metal absorption tube and glass casing,and between glass casing and the outside environment are analyzed.What’s more,the heat collecting efficiency,exergetic efficiency and vaporization efficiency of the system are deduced.(2)Establishment of the parabolic trough collector test system and preparation of lithium bromide solution.An experimental test system of the parabolic trough collector is set up,the parameters and experimental procedure of solar energy solution generator are introduced in detail,and the system error is also calculated.Besides,Lithium bromide solution with mass concentration of 40% was prepared for experimental research,and the heat of solution of lithium bromide was measured in the process of solution preparation.Results show that heat value of lithium bromide was 353.21 k J/kg.Thus,lithium bromide can be used as a heat storage material as well as a hygroscopic material.(3)Study on heat absorbing and vaporization performance of lithium bromide solution in parabolic trough collector.After one year research,the results show that: 1)the all-day average vaporization efficiency of the system with preheating process is 0.19 which is 3.8 times higher than the system without preheating process.2)The all-day average vaporization efficiency in spring is the lowest with the value of 0.19 and the value in summer was the highest,reaching 0.32.Otherwise,the all-day average vaporization efficiency in autumn and winter were 0.28 and 0.27,respectively.During all of the testing days of the year,the average daily heat collection efficiency was 0.47 and the average daily vaporization efficiency was 0.26.