Calculation of Metzner Constant for Double Helical Ribbon Impeller by Computational Fluid Dynamic Method

用多重参考框架(MRF ) impeller 方法，一条双螺旋状的带子(DHR ) 产生的三维的非牛顿的流动地 impeller 被模仿了。数字模拟计算的速度地类似于以前的研究，力量常数与试验性的数据同意了很好。三计算液体动态(CFD ) 方法，标记我， II 和 III，被用来计算 Metzner 经常的 ks。结果证明从 slop 方法的计算价值(方法我) 与试验性的数据一致。方法 II，它拿了最大的圆周一般水准砍在是的 impeller 附近的率有效砍计算 ks 的率，对实验的也显示出的好同意。然而，两个方法受不了计算过程的复杂性。一个新方法(方法 III ) 在这份报纸被设计为精明的 ks 在 impeller 附近把区域加权的平均粘性用作有效粘性。方法 III 显示出好精确性和容易使用。

Synthesis of a nitrogen-doped titanium dioxide-reduced graphene oxide nanocomposite for photocatalysis under visible light irradiation

A nitrogen-doped titanium dioxide-reduced graphene oxide (N-TiO2-RGO)nanocomposite has been synthesized by the combination of a hydrothermal method and a thermal treatment under a NH3/N2 atmosphere.The resulting composites are characterized by Fourier transform infrared spectroscopy, scanning electron microscopy,transmission electron microscopy,diffuse reflectance absorption spectroscopy,energy-dispersive X-ray spectroscopy,and Raman characterization techniques.The sequence of the thermal treatment and hydrothermal treatment processes is shown to influence the photocatalytic activity of nitrogen-doped composites.The composites synthesized by using this method show better photocatalytic activities toward the degradation of acetaldehyde under visible light irradiation compared with P25,N-TiO2,and TiO2-RGO.By applying the thermal treatment process after the hydrothermal pro- cess,nitrogen atoms can be simultaneously doped in the lattice ofTiO2nanoparticles and on the surface of reduced graphene oxide sheets.The conversion of acetaldehyde,as the model molecule of volatile organic compounds,is measured in a continuous stirred-tank reactor until the steady state condition is reached. The conversion of 50 ppm acetaldehyde,in an air flow under illumination from an 80W Hg lamp with a UV cut-off filter,reaches 62% after a 1-h reaction using a 0.07g N-TiO2-RGO sample with an optimum loading of 2wt% graphene oxide.In comparison,the photocatalytic activity of P25 for the degradation of acetaldehyde under visible light irradiation is only 8% under the same reaction conditions.The reaction rates for acetaldehyde degradation are calculated and predicted with pseudo-first-order reaction kinetics,and the activity result of the best N-TiO2-RGO sample is 12.3times higher than for P25.