Results are presented of an ongoing investigation into modeling friction in fiuidized dense-phase pneumatic transport of bulk solids. Many popular modeling methods of the solids friction use the dimen- sionless solids...Results are presented of an ongoing investigation into modeling friction in fiuidized dense-phase pneumatic transport of bulk solids. Many popular modeling methods of the solids friction use the dimen- sionless solids loading ratio and Froude number. When evaluated under proper scale-up conditions of pipe diameter and length, many of these models have resulted in significant inaccuracy. A technique for modeling solids friction has been developed using a new combination of dimensionless numbers, volu- metric loading ratio and the ratio of particle free settling velocity to superficial conveying air velocity, to replace the solids loading ratio and Froude number. The models developed using the new formalism were evaluated for accuracy and stability under significant scale-up conditions for four different prod- ucts conveyed through four different test rigs （subject to diameter and length scale-up conditions）. The new model considerably improves predictions compared with those obtained using the existing model, especially in the dense-phase region. Whereas the latter yields absolute average relative errors varying between 10% and 86%, the former yielded results with errors from 4% to 20% for a wide range of scale-up conditions. This represents a more reliable and narrower range of prediction that is suitable for industrial scale-up requirements.展开更多
In this work, the effects of ratio of monomer to cross-linker(AM/MBAM) and solid loading on the microstructure and mechanical properties of porous Si3N4 ceramics prepared by tert-butyl alcohol(TBA)-based gel-casting p...In this work, the effects of ratio of monomer to cross-linker(AM/MBAM) and solid loading on the microstructure and mechanical properties of porous Si3N4 ceramics prepared by tert-butyl alcohol(TBA)-based gel-casting process were investigated. It was found that, when the ratio of monomer to crosslinker was 8, and the solid loading was 50 wt%, the mechanical properties of sintered samples were the most excellent, which resulted from the uniform pore size distribution and well-grown rod-like bSi3N4 grains. In that case, the porosity and flexural strength of sintered samples were 50% and 125 MPa,respectively.展开更多
文摘Results are presented of an ongoing investigation into modeling friction in fiuidized dense-phase pneumatic transport of bulk solids. Many popular modeling methods of the solids friction use the dimen- sionless solids loading ratio and Froude number. When evaluated under proper scale-up conditions of pipe diameter and length, many of these models have resulted in significant inaccuracy. A technique for modeling solids friction has been developed using a new combination of dimensionless numbers, volu- metric loading ratio and the ratio of particle free settling velocity to superficial conveying air velocity, to replace the solids loading ratio and Froude number. The models developed using the new formalism were evaluated for accuracy and stability under significant scale-up conditions for four different prod- ucts conveyed through four different test rigs （subject to diameter and length scale-up conditions）. The new model considerably improves predictions compared with those obtained using the existing model, especially in the dense-phase region. Whereas the latter yields absolute average relative errors varying between 10% and 86%, the former yielded results with errors from 4% to 20% for a wide range of scale-up conditions. This represents a more reliable and narrower range of prediction that is suitable for industrial scale-up requirements.
基金supported by the National Natural Science Foundation of China (No. 90816018)Program of Shaanxi Bureau of Foreign Expert Affairs (No. 2011-32)
文摘In this work, the effects of ratio of monomer to cross-linker(AM/MBAM) and solid loading on the microstructure and mechanical properties of porous Si3N4 ceramics prepared by tert-butyl alcohol(TBA)-based gel-casting process were investigated. It was found that, when the ratio of monomer to crosslinker was 8, and the solid loading was 50 wt%, the mechanical properties of sintered samples were the most excellent, which resulted from the uniform pore size distribution and well-grown rod-like bSi3N4 grains. In that case, the porosity and flexural strength of sintered samples were 50% and 125 MPa,respectively.
