Study On Energy Conversion Characteristics Of The Direct Absorption Solar Thermochemical Suspension Reactor

At present,human beings are facing environmental pollution and energy shortages the two major problems,solar energy has been widely concerned because of its various advantages,that is being abundant,pollution-free clean.As a new type of solar thermal utilization technology,solar thermochemical conversion technology can not only solve the problem of uneven distribution of solar energy,but also get other high-grade energy.Solar thermochemical reactor / collector is the core component that achieves energy conversion,the present research focuses on improving the heat-absorption efficiency and energy conversion efficiency of the reactor.The solar thermochemical suspension reactor directs absorption solar energy by the suspension of particles,in this reaction chamber,the more uniform heat distribution can be obtained,the heat collecting efficiency is improved,and the heat load on the inner wall can be reduced,therefore,it has good prospects for development and application.Firstly,the Mie theory is used to calculate the thermal radiation characteristics of the suspension of particles in the reactor.It is found that the attenuation coefficient of the suspension with large particle size in the band from 0.2μm to 1.5μm are not obvious,and the value is small under a certain mass flow rate,but the suspension with small particle size has large variable attenuation coefficients with wavelength.The position of attenuation coefficient peak was shifted to long-wave band with the increase of particle size.When the particle diameter is 0.5μm,increasing the mass flow of particles can significantly improve the attenuation coefficient of the suspension in the band from 0.2μm to 4μm.Secondly,the vortex-flow reactor that direct absorption solar was set up,and the experimental study on the heat transfer characteristics of the suspension with different mainstream flow rate and auxiliary airflow rate is carried out.The experimental results show that there is a phenomenon of particle contamination on the surface of quartz glass,increasing the flow rate of auxiliary airflow will reduce the pollution of the glass and raise the temperature of the center of the cavity.The numerical simulation of the flow field and temperature field in the experimental device was carried out by using Fluent,the results show that some of the particles will move toward the glass,which is consistent with the experimental.Increasing the flow rate of the auxiliary airflow can reduce the particle concentration on the glass surface.Finally,the heat transfer characteristics of the solar cracking reactor with helical groove structure was analyzed,and the numerical simulation of hydrogen production from methane decomposition was carried out.The results show that the addition of carbon particles in air can obtain a more uniform temperature distribution,and increase the conversion rate of the reaction.When CH4 flow rate was 0.5m/s,and Ar flow rate was 1m/s,add carbon particles with mass flow rate of 10-5kg/s,H2 and C production increased 1.43mol/m3 and 0.56mol/m3 respectively.The increase of the main flow rate can enhance swirl and increase the moving distance,but at the same time,particles are move faster,so the residence time of particles is reduced,which is unfavorable to both thermal performance and reaction.In order to enhance the yield of hydrogen,small particles should be used or increasing the mass flow rate of particles.