| The linear Fresnel solar collector is able to change direct solar radiation of low energy density to that of high energy density and heat working fluid to 100℃~250℃so as to supply heat to solar absorption chiller.The common BrLi-water chiller works by single or double effect absorption refrigeration cycle.The single effect chiller has a low requirement on heat source and will work when the heat temperature is greater than 85℃but the COP will merely increase with the temperature’s rising.Meanwhile,the double effect chiller won’t work until the temperature of heat source is greater than 140℃.However,the temperature of the heat supplied by the Fresnel collector is usually unsteady and varies up and down.Furthermore,it is mostly in the range of110℃~140℃where the double effect chiller cannot work and the single chiller can’t make full use of the heat energy.Therefore,1.n effect BrLi-water chiller,working between the single and double effect refrigeration cycle,is invented to match the heat source provided with Fresnel collector.The main work of this paper is the research on a 1.n effect solar chiller driven by Fresnel collector with a semicircular cavity absorber and the brief contents are as follows.(1)Optical characteristics of the linear Fresnel collector.Starting with the design method on mirror field,mathematical model is established to calculate the optical losses of the collector and the influence on optical efficiency brought by them.Furthermore,optical simulation model is set up to simulate the focusing process of sunlight to analyze the energy change of the concentration.Also the radiation heat flux density distribution in the cavity absorber is gained.Result shows the optical efficiency of collector which is 66.5%.(2)Heat collecting performance of the Fresnel collector.Analysis is carried out to gain the heat loss,heat loss coefficient and heating collecting efficiency.And numerical simulation model is established to simulate the solar-thermal conversion occurred in the semicircular cavity absorber.Also,the experiment is done to test the efficiency of the collector.The simulation results show that the heat loss coefficient is between38.99W/m~2K~56.6W/m~2K,where the radiation loss accounts for about 1/3,when the working temperature is in the range of 100℃~180℃.At last,the heat collecting efficiency of the collector is up to 52.5%when working temperature is 150℃.(3)Simulation on variable effect absorption solar cooling system.The model of the 1.n effect BrLi-water chiller is set up using ANN method and the modules of Fresnel collector and 1.n effect absorption chiller are compiled and built in TRNSYS where the solar cooling simulation system is completed.The result shows that,the collector’s efficiency is up to68.8%,and the maximum working temperature is about 147℃.COP of the bromine-water chiller varies between 0.84-1.05.And the COP of solar cooling system can reach 0.53,while the average value is 0.41.(5)Experimental research on solar thermal cooling and cooling and power generation system.The experiment bench of the solar thermal utilization in cooling and power generation system is built up.In the case of good solar radiation,the collector’s working temperature can reach172.5℃and the collector’s efficiency is up to 56.8%.The 1.n effect bromine-water chiller is rated at 50kW and achieve the max COP 1.05 in operation. |
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