静止颗粒群热辐射吸收性能的蒙特卡罗法二维数值研究

Thermal Radiation Absorption Properties of Two-Dimensional Stationary Particle Groups Based on the Monte-Carlo Method

在粒子式太阳能接收器中吸热效率与出口温度难以兼顾,而颗粒群热辐射吸收性能决定其热效率及升温上限,基于蒙特卡罗法建立了外部平行辐射投射下的静止颗粒群辐射传递模型,探究颗粒群几何构型、颗粒粒径、颗粒辐射物性、辐照条件等因素对热辐射传输的影响。结果表明:颗粒群吸热时间与粒径、空间构型无关;但与体积分数成正比,且随外部辐射强度或颗粒表面吸收率的增大而缩短。对给定颗粒群,平衡温度主要依赖于外部辐射强度;总体吸收率主要取决于颗粒表面吸收率。给定空间构型下,二者均与颗粒粒径正相关,且随体积分数的增大具有相似的变化规律。不同空间构型下,颗粒体积分数的增大均在强化吸收外部辐射的同时增大了自发辐射的逸出。现有构型中,棋盘交错型、扇型与随机型下的总体吸收率随体积分数的增大有峰值存在。扇型与随机型达到最高平衡温度和效率所需的颗粒浓度最小。根据计算结果提出了颗粒群总体吸收率经验关联式,其中有82.9%的计算结果与定义式计算值相对误差小于15%。该研究结果可为运动颗粒群辐射传递的计算、粒子式太阳能吸收器的设计提供参考。

It is difficult to balance the high heat absorption efficiency and high outlet temperature in the particle solar receiver,and the thermal radiation absorption performance of particles determines its thermal efficiency and the upper limit of temperature rise.Therefore,based on the Monte-Carlo method,a radiative transfer model of stationary particle groups under external parallel radiation projection is established to investigate the effects of the geometry structure of particle groups,particle sizes,particle radiative properties,irradiation conditions and other factors on the transmission of thermal radiation.The results show that the particle groups’absorption duration is independent of the particle size and geometry structure,but is in direct proportion to the volume fraction,and shortens with the increase of the external radiation intensity or the absorptivity on the particle surface.For a certain particle group,the equilibrium temperature depends mainly on external radiation intensity,and the overall absorption rate relies mainly on the absorptivity of particle surface.For a given geometry structure of the particle group,both are positively correlated with the particle size,and have similar variation behavior as the volume fraction increases.In different geometry structures,increasing the volume fraction of particles enhances the external radiation absorption while increasing the escape of self-generated radiation.Among the existing structures,the overall absorptivity under the tessellated staggered structure and the sector structure have peaks with the increase of volume fraction.Of these,the sector structure requires the smallest particle concentration to reach the highest equilibrium temperature and efficiency.According to the calculation results,an empirical correlation formula for the overall absorptivity of the particle population is proposed,whose relative error subject to the definition formula calculation value is less than 15%.The results of this paper can provide a reference for the computation of radiation transfer of moving particle populations,as well as the design and regulation of particle solar receivers.