Search

Abstract: The knowledge of thermal properties of technical components or internals in chemical reactors is often a key characteristic for planning and designing chemical engineering processes. As an alternative to packed beds or packings, sponges turned out to be used in new application fields in chemical and process engineering. Therefore an experimental study was performed to investigate the two-phase thermal conductivity of solid ceramic sponges made of alumina, mullite and oxidic-bonded silicon carbide (OBSiC) at moderate temperatures. A two-dimensional model is used for analysing the measured temperature profiles and for calculating the thermal conductivity. It can be observed, that the thermal conductivity increases with decreasing porosity and is nearly constant when the pore size (ppi number) is varied. The thermal conductivity data are modelled by an approach similar to the well known Krischer model. Compared to a packed bed of spherical particles, the values of the thermal conductivity of sponges turn out to be about five times higher. [Copyright &y& Elsevier]

Abstract: According to the fact that long-term excess-standard CO in low-to-medium metamorpic grade coal seams has not caused coal spontaneous ignition, this paper has carried out the experimental research on adsorption test of eight typical coal samples with different maceral compositions on CO under different pressures. Comprehensive thermodynamic studies on the corrected adsorption volume were conducted by applying physical chemistry, interface chemistry, coal petrology and coal chemical engineering knowledge. Adsorptivity was evaluated from three aspects, including specific surface area, adsorption capacity on per surface area, and interaction between CO molecule and coal surface. The results show that the adsorption of inertinite is better than that of vitrainite. The change rule in free energy of coal surface under different balance conditions shows that the surface free energy of coal samples with higher vitrinite content is greater than that with higher inertinite content. This explais the main reason why the inertinite has a better adsorption. The isosteric heat of coal samples with higher inertinite content is greater than that with higher vitrinite content and the interaction between CO molecular and coal morphology in coal samples with higher inertinite is greater than that with higher vitrinite. [Copyright &y& Elsevier]

Abstract: Many fibrous materials such as nonwoven materials are often consolidated by means of hot calenders, i.e., hot compaction rolls. Hot calendering compresses the fiber assembly and can cause changes in the structure. In nonwovens, calendering has an added function of thermally bonding the fibers at their respective crossovers to form a strong but yet somewhat porous material. Calendering causes a significant increase in the solid volume fraction (SVF) of the media and therefore, affects their permeability. To our knowledge, no work in the literature has been dedicated to modeling the permeability of calendered nonwovens. In this study, virtual nonwoven structures are generated and compressed from top and bottom to resemble the hot calendering process. In agreement with our experimental observations, it was found that the average SVF profile across the material''s thickness turns into a U-shape profile after the calendering. In this work, the dimensionless permeability of the calendered media is computed using CFD tools and reported for different compaction ratios. Results of our simulations are compared with the experiment as well as the available empirical and/or analytical permeability models in the literature and good agreement, depending upon the SVF, is observed. We also studied the influence of orientation distribution of the fibers on the dimensionless permeability of the fabric and noticed that permeability decreases by increasing the directionality of the fibers. This is found to be primarily due to the fact that highly oriented uncompressed fiber-webs tend to have a higher SVF. Fiber-webs of identical SVF, however, exhibited almost identical permeabilities regardless of their fiber orientations. [Copyright &y& Elsevier]