Study On Heat Flux Homogenization Mechanism Of Carbon Dioxide Carbon Aerosol Solar Cavity Receiver

Cavity heat receiver is an important equipment of tower solar thermal power generation system.Its main function is to absorb solar energy and heat working medium for subsequent power generation system.Due to the non-uniform distribution of solar heat flux and temperature on the wall of the heat receiver,the local overheating leads to the burning of key components,which reduces the safety of the whole system.In order to solve the problem of highly uneven distribution of solar heat flux and temperature on the wall of the heat receiver,a new method of homogenizing the distribution of solar heat flux by filling the heat receiver with aerosol particles was proposed.In order to determine the types of aerosol gases,the average absorption coefficients of carbon dioxide,carbon monoxide and methane were compared by Edwards index wide band model.The results show that the average absorption coefficient of carbon dioxide is the largest compared with the other two gases,and can be used as the filling gas of aerosol.In order to determine the types of aerosol solid particles,Mie scattering theory was used to study the attenuation factor,absorption factor,scattering factor,scattering phase function and other radiation characteristic parameters of carbon particles and aluminum oxide particles.The results show that compared with aluminum oxide particles,the absorption factor and scattering phase function of carbon particles are the largest,the attenuation factor and scattering factor are the smallest,which can be used as reference As aerosol filler particles.Therefore,the solid particle aerosol filled in the heat receiver is carbon dioxide carbon aerosol.On this basis,the Monte Carlo ray tracing(MCRT)method is used to study the influence of carbon particle number density on the solar heat flux distribution on the wall,solar radiation energy absorption and spatial heat flux distribution of the cube cavity heat receiver.The results show that when carbon particles are not filled,the gas in the receiver is almost diathermal,and its space heat flux is almost zero.The heat flux density and absorbed solar radiation energy of the direct sunlight wall are much larger than that of the side,which is the concentrated embodiment of the non-uniformity of heat flux density.On the other hand,the side is small and uniform.After the carbon particles are filled,the heat flux density of the direct sunlight wall and the absorbed sunlight radiation energy decrease sharply,and the space heat flux density increases continuously,which greatly improves the uniformity of the whole space and the wall heat flux density,while the heat flux density level of the side wall is not high and the change is not obvious.For space,because the absorption and scattering of carbon particles are carried out in the whole space,the heat flux gradually decreases with the deepening of sunlight.In addition,the heat loss of the quartz glass window of the square cavity heat receiver is studied by using the computational fluid dynamics(CFD)numerical simulation method.The results show that the radiation heat loss is greatly affected by the temperature,and is almost not affected by the wind speed and wind direction angle;The convective heat loss is greatly affected by temperature,wind speed and wind direction angle.Based on the cube cavity heat receiver,the Monte Carlo ray tracing-finite volume method(MCRT-FVM)coupled calculation model is used to study the influence of carbon particle number density and carbon dioxide concentration on the wall heat flux and temperature distribution,space heat flux distribution and evaporation of the three-dimensional cavity heat receiver filled with carbon aerosol and arranged with heat absorbing pipes.The results show that:(1)when the number density of carbon particles is small,the heat flux density and temperature of the direct sunlight wall are much higher than those of the other surfaces,which is the concentrated reflection of the non-uniformity of heat flux density,while the amount of the other surfaces is small and uniform;with the increase of the number density of carbon particles,the heat flux density and temperature of the direct sunlight wall decrease sharply,and the space heat flux increases continuously,resulting in the heat flux of the whole space and wall The density uniformity is greatly improved,while the heat flux and temperature level of other walls are not high.For space,because the absorption and scattering of carbon particles are carried out in the whole space,the heat flux gradually decreases with the deepening of sunlight.Finally,the evaporation capacity of the heat receiver is increased.(2)Carbon dioxide has little effect on the wall heat flux and space heat flux,and the wall temperature and evaporation increase slightly due to the increase of infrared radiation energy absorbed by carbon dioxide.The method of filling carbon dioxide and carbon aerosol inside the cavity heat receiver can significantly improve the uniformity of solar heat flux distribution on the wall of the cavity heat receiver,and has the advantages of simple operation,low cost,practical and efficient,which will greatly improve the evaporation capacity and safe operation cycle of the solar cavity heat receiver,It has broad application prospects and important social significance and economic value.