The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electri...The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.展开更多
A mathematic model is developed for the perovskite-type mixed ionic-electronic conducting(MIEC) membrane,which makes it possible to simulate the process of oxygen separation in the U-shaped Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_...A mathematic model is developed for the perovskite-type mixed ionic-electronic conducting(MIEC) membrane,which makes it possible to simulate the process of oxygen separation in the U-shaped Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_3-δhollow-fiber membrane. The model correlates the oxygen permeation flux to the measurable variables. The trends of calculated results for purge operation coincide well with the experimental data, therefore the model is considerable for flux prediction under vacuum operation. Higher oxygen separation efficiency can be achieved with vacuum operation than purge operation. Parameter study with vacuum operation reveals that oxygen permeation flux increases with higher vacuum levels, and vacuum pressure of around 1.013 × 10~3 Pa is the optimal.Also, vacuum operation on the lumen side is much more efficient to achieve higher oxygen permeation flux compared with compression mode on the shell side.展开更多
A 3-dimensional unit cell model is developed for analyzing effective thermal conductivity of xonotlite-aerogelcomposite insulation material based on its microstructure features. Effective thermal conductivity comparis...A 3-dimensional unit cell model is developed for analyzing effective thermal conductivity of xonotlite-aerogelcomposite insulation material based on its microstructure features. Effective thermal conductivity comparisonsbetween xonotlite-type calcium silicate and aerogel as well as xonotlite-aerogel composite insulation material arepresented. It is shown that the density of xonotlite-type calcium silicate is the key factor affecting the effectivethermal conductivity of xonotlite-aerogel composite insulation material, and the density of aerogel has little influence.The effective thermal conductivity can be lowered greatly by composite of the two materials at an elevatedtemperature.展开更多
基金The National Natural Science Foundation of China(No.50906073,31070517)China Postdoctoral Science Foundation(No.20110491332)+1 种基金Jiangsu Planned Projects for Postdoctoral Research Funds(No.1101009B)the Science and Technology Development Plan of North Jiangsu(No.BC2012444)
文摘The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.
基金Supported by the National Science Fund for Distinguished Young Scholars of China(21225625)the Natural Science Foundation of China(21176087)the Specialized Research Fund for the Doctoral Program of Higher Education(20110172110013)
文摘A mathematic model is developed for the perovskite-type mixed ionic-electronic conducting(MIEC) membrane,which makes it possible to simulate the process of oxygen separation in the U-shaped Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_3-δhollow-fiber membrane. The model correlates the oxygen permeation flux to the measurable variables. The trends of calculated results for purge operation coincide well with the experimental data, therefore the model is considerable for flux prediction under vacuum operation. Higher oxygen separation efficiency can be achieved with vacuum operation than purge operation. Parameter study with vacuum operation reveals that oxygen permeation flux increases with higher vacuum levels, and vacuum pressure of around 1.013 × 10~3 Pa is the optimal.Also, vacuum operation on the lumen side is much more efficient to achieve higher oxygen permeation flux compared with compression mode on the shell side.
基金supported by the National Natural Science Foundation of China (No.50806021)Program for Changjiang Scholars and Inn ovative Researeh Team in University (PCSIRT0720).
文摘A 3-dimensional unit cell model is developed for analyzing effective thermal conductivity of xonotlite-aerogelcomposite insulation material based on its microstructure features. Effective thermal conductivity comparisonsbetween xonotlite-type calcium silicate and aerogel as well as xonotlite-aerogel composite insulation material arepresented. It is shown that the density of xonotlite-type calcium silicate is the key factor affecting the effectivethermal conductivity of xonotlite-aerogel composite insulation material, and the density of aerogel has little influence.The effective thermal conductivity can be lowered greatly by composite of the two materials at an elevatedtemperature.
