Thermal and chemical reaction performance analyses of steam methane reforming in porous media solar thermochemical reactor

In order to investigate the thermochemical reaction performance of steam methane reforming (SMR), the steady heat and mass transfer model coupled with thermochemical reaction kinetics is developed for the volumetric porous media solar thermochemical reactor. The local non-thermal equilibrium (LNTE) model with modified P1 approximation is adopted to investigate the temperature distributions of the solid phase and fluid phase. For the solid phase energy equation, the irradiative heat transfer coupled with chemical reaction kinetics is programmed via User Defined Functions (UDFs). The concentrated solar irradiation is not only considered as the boundary condition at the reactor front surface, but also as the irradiative heat source in the whole volume of reactor. The parametric studies are conducted to investigate the thermal and hydrogen production performances as a function of operational parameters. The numerical results indicate that SMR reaction has big effects on temperature distribution. The generated H₂ mole fraction decreases sharply with the increasing of fluid inlet velocity, porosity and mean cell size. The generated H₂ mole fraction increases significantly with the increasing of incident solar irradiance.     

颗粒抗滚动作用对水合物沉积物宏观及微观力学特性的影响

因其清洁无污染且储量巨大,天然水合物被认为是21世纪重要的战略资源。为有效考虑水合物沉积物中由于不规则的颗粒形状对宏观响应产生的影响,在离散元数值模拟中引入抗滚动线性接触模型,对抗滚动系数为0、0.2、0.4、0.6、0.8以及不同饱和度(10%、20%、30%、40%)的水合物沉积物数值试样进行了20组常规三轴压缩试验,探究了抗滚动作用对水合物沉积物的宏观力学特性的影响及微观作用机理。研究结果表明:抗滚动作用可以有效提高水合物沉积物的宏观强度和剪胀程度,但是抗滚动作用对于强度和剪胀的促进作用并不会无限增大,而是存在一个临界值,大于临界值之后,抗滚动作用对宏观力学特性的影响越来越小。这是由水合物沉积物内部微观结构的演化决定的:抗滚动系数的增大,虽然配位数降低,孔隙率有所增加,但颗粒的平均接触力将会随之增大,内部形成贯穿试样的强力链,从而使沉积物体系更加稳定,而当抗滚动系数增大至特定值时,平均接触力、配位数以及孔隙率受到抗滚动作用的影响逐渐减小,从而使水合物沉积物的宏观力学特性受到抗滚动作用的影响也会越来越小。