Research On Modification Of High Temperature Radiation Absorption Properties Of Solid Particles Based On Surface Coating

In solid particle solar receivers(SPSRs),solid particles have always been a research hotspot as heat transfer fluids and thermal energy storage media.The use of coatings with different thermodynamic and optical properties can adjust and improve the comprehensive performance of solid particles.Therefore,this paper studies the properties of manganese iron black coatings and the coating effects on different solid particles.In this paper,manganese iron black coatings were prepared by sol-gel method.Powders with different properties were obtained by changing the ratio of Fe/Mn and characterized by experiments.Compared with pure Fe2O3,the spectral absorption rate of manganese iron black is greatly improved,and it has excellent thermodynamic properties.When the Fe/Mn ratio is 4:1,the overall performance of the coating is more excellent.Considering the cost and properties of solid particles,quartz sand,bauxite and mullite were selected as matrix particles for coating experiments.In the coating experiment,4:1 manganese iron black was applied to the surface of the matrix particles by water bath method to obtain the coated particles.When the mass ratio of the coating to the matrix particles was 0.75:1 before the experiment,the effective mass ratio was 0.3:1,and the coating thickness tended to be stable at 20.91μm.The spectral absorptivity of the three coated particles is greatly improved compared with that before the coating,but the coated quartz sand falls off a lot at high temperature,and the coverage effect of the coated bauxite is not complete.Only the coating effect and thermal stability of the coated mullite reach a very good level.Thermal stability and wear resistance experiments were performed using coated mullite.The experimental results show that there is no significant change in the spectral absorptivity of the coated mullite at a high temperature of 900℃ and after 30 thermal cycles.The mass loss does not exceed 0.392%and the coating thickness loss does not exceed 0.263μm.After 10 hours of wear at 900 rpm,the loss is more obvious,the mass loss reaches 8.244%,the coating thickness loss is 27%,and the spectral absorption rate is also reduced by 3.88%.The possible reason is that a small amount of coating damage exposes the surface of mullite.This work lays a foundation for further detailed experimental study of solid particle coating to improve absorption and heat transfer enhancement,thus providing a new choice for improving the system efficiency of solar particle receivers.