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Chengtang Liu,Huaming Li,Hui Xu,Ling Liu,Li Xu,Zhixiang Ye 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.4
Na_8Nb_6O_19.13H_2O particles were synthesized by a simple hydrothermal method. The catalysts were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and thermogravimetric and differential scanning (TG-DSC). The XRD and TG-DSC analyses indicated that Na_8Nb_6O_19.13H-2O was an intermediate hexaniobate during the preparation of NaNbO_3 powders. Methylene blue (MB) dye degradation using Na_8Nb_6O_19.13H_2O/H_2O_2,Nb_2O_5/H_2O_2 and NaNbO_3/H_2O_2 systems were investigated, respectively. Among the catalytic oxidation systems, Na_8Nb_6O_19·13H_2O showed the highest activity for degradation of MB in the presence of H_2O_2. The results indicated that the dye degradation efficiency could be 93.5% at 30 ℃ after 60 min in the presence of the Na_8Nb_6O_19·13H_2O/H_2O-2 system. It was also found that the degradation of MB over the catalytic systems followed pseudo-first-order kinetics, and the degradation rate was 0.02376 min−1 in the Na_8Nb_6O_19.13H_2O/H_2O_2 system, which was higher than that in the Nb_2O_5/H_2O_2and NaNbO_3/H_2O_2 systems. A possible mechanism for MB catalytic oxidation degradation using the Na_8Nb_6O_19.13H-2O/H_2O_2 system was proposed.
Numerical simulation of slit wall effect on the Taylor vortex flow with radial temperature gradient
Dong Liu,Chang-qing Chao,Fang-neng Zhu,Xi-qiang Han,Chengtang Liu 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.4
Numerical simulation was applied to investigate the Taylor vortex flow inside the concentric cylinders with a constant radial temperature gradient. The reliability of numerical simulation method was verified by the experimental results of PIV. The radial velocity and temperature distribution in plain and 12-slit model at different axial locations were compared, and the heat flux distributions along the inner cylinder wall at different work conditions were obtained. In the plain model, the average surface heat flux of inner cylinder increased with the inner cylinder rotation speed. In slit model, the slit wall significantly changed the distribution of flow field and temperature in the annulus gap, and the radial flow was strengthen obviously , which promoted the heat transfer process at the same working condition.