Research On Modeling Simulation And Performance Analysis Of The Key Components In Solar~+ Multiple Heat Sources System

With the intensification of global problems such as unreasonable energy utilization structure and deteriorating natural environment,renewable energy has received widespread concerns from whole society.It is known that it will gradually become the replacement of coal and oil and dominate energy consumption in the foreseeable future.As one of the ’main force’,solar energy has been developed and utilized in commercial and residential fields over the years.On the basis of the continuous development and improvement of solar thermal utilization technology,Solar+multiple heat sources system was derived.Solar energy was considered as the main heat source and other forms of energy are selected as supplements according to local conditions in this system,which has been proved to be high-efficiency,environmental friendly,operational stability and cost-saving.On account of the characteristics of energy distribution with abundant solar energy resources,large natural gas reserves but lack of water resources in the inland areas of northwest China,a novel solar+ multiple heat sources system used for industrial thermal processing,crop drying,water heating or residential heating in winter,was proposed.The solar energy was regarded as the main heat source,while the natural gas boiler and air source heat pump were chosen to be auxiliary heat sources.The solar radiation energy would be made full use of in fine weather,the latter two,however,would become dominant under the extreme working conditions.Therefore,energy efficiency was improved and problems caused by the large-scale use of fossil fuels were avoided simultaneously.Air instead of water was selected as the heat transfer medium in solar collector of the proposed system,which effectively alleviated the pressure of water-using in that region.What’s more,defects such as freezing,leakage,scaling and corrosion of the pipe were avoided.A parallel internal structure was designed in new solar collector,and the simulation calculation was carried out by using CFD simulation software Fluent 14.5 to investigate its operating performance.Compared with the traditional evacuated tube and U-tube collector,the new one possessed a preferable heat transfer and flow performance.Numerical method was applied to optimize the preliminary design of the new collector.Environmental and structural factors that can affect the performance of the collector were determined.Controllable parameters including inlet air mass flow rate,tilt angle,inner diameter and length of the metal tube,and the inlet length of the manifold were confirmed as the optimization objects.The optimization value of each factor was determined respectively,all of which constitute the optimal parameter combination as an optimization scheme for the presented collector.Radial staggered internally finned tubes were applied in the gas boiler heat exchanger of the system,which can remarkably improve its heat transfer performance.The simulation results showed that,the shape of y=16x2 finned tube with 16 fins achieved a better comprehensive performance,which was also verified by the theory of field synergy.The self-defined function(UDF)was compiled to simulate the condensation process inside the tube.The enhanced heat transfer mechanism of the new finned tube was analyzed by the distribution of water vapor mass fraction and liquid film.