A method was developed to quickly evaluate the streak line pattern in a laminar mixing vessel by numerical analysis. The primary flow in a laminar mixing vessel is the rotational flow, but the secondary flow as the upper and lower circulation flow determines the quality of the mixing. The three-dimensional steady velocity component of r–θ–z was regarded as the two-dimensional non-steady velocity component of r–z–t. As a result, the calculated streak line pattern agreed qualitatively well with the experimental pattern, and calculating time was reduced substantially. By using the present method to translate the three-dimensional steady flow to a two-dimensional unsteady flow, streak line patterns were easily visualized from video data with PIV at low Reynolds number. It was found that the mixing performance of impellers, including some wide-paddle impellers developed by a Japanese company, could be estimated quickly by this method.
In recent years, the gap of energy demand among seasons or between daytime and nighttime in Japan are steadily expanding, and technological development concerning effective use of energy is an urgent issue coupled with recent environmental problems. We focus on fatty acids (capric acid, lauric acid and myristic acid) and their mixture having unique phase change characteristics as a working fluid for a heat exchange system with multistage latent heat storage. These fatty acids as heat storage materials are easy to handle and less influenced on human body near ambient conditions. When the fatty acids mixed with a suitable mixing ratio are in the liquid phase state, the thermophysical properties (density, viscosity, melting and freezing points, supercooling character, effects of mixing ratio and so on) were identified in order to establish a new heat exchange system with multistage latent heat storage. As a result, thermophysical properties of the fatty acids and their mixture were evaluated quantitatively and were newly proposed as an appropriate heat transfer database.
A single polymer electrolyte fuel cell (PEFC), normally operated at 60–80°C, was operated at 90°C. The in-plane temperature distribution on the back of separator at the cathode was measured by thermograph for various combination of polymer electrolyte membrane (PEM) and gas diffusion layer (GDL) thickness and relative humidity of supply gases, and the difference in heat and mass transfer characteristics and power generation characteristics under different conditions were investigated.
With the thickest PEM, Nafion 115, the influence of the relative humidity of supply gas on the power generation characteristics decreased with decreasing GDL thickness. With a thin GDL, PEM is humidified by the enhanced transfer of water from the high to the low relative humidity side. By the same effect, in-plane temperature distribution from the inlet to the outlet was flat. On the other hand, investigation of the impact of thickness of PEM on the power generation characteristics with a thin GDL, TGP-H-030, the relative humidity of supply gas had little effect on the power generation characteristics regardless of PEM thickness, because PEM and catalyst layer are humidified by the enhanced water transfer through the thin GDL. However, the power generation performances of Nafion NRE-212 and Nafion NRE-211 were higher than that of the thicker Nafion 115, since the thinner PEMs were thought to have lower ohmic resistance. The in-plane temperature distribution with Nafion 115 and Nafion NRE-211 was flat, while that with Nafion NRE-212 increased from the inlet to the outlet as a result of the power generation performance and water transfer characteristics.
The combination of the thinnest PEM and GDL, Nafion NRE-211 and TGP-H-030, was found to be the optimal for the high temperature operation at 90°C from the viewpoint of the power generation performance as well as control of the in-plane temperature distribution.
Vapor–liquid equilibrium measurements in (CO2(1)–ethanol(2)–myrcene(3)) and CO2(1)–ethanol(2)–linalool(3)) ternary systems were carried out at temperatures of 333–373 K and pressures of 6–10 MPa with a continuous flow apparatus for selective separation of essential oil components. The experimental data were correlated with the results calculated with the Peng–Robinson equation of state combined with the van der Waals mixing rule based on fundamental critical properties estimated by a group contribution method. In counter-current extractions in CO2(1)–ethanol(2)–myrcene(3)–linalool(3) systems for myrcene and linalool, the purity of myrcene reached about 90 mol% at 333 K and 6 MPa from an equimolar feed of myrcene and linalool. From the results of supercritical counter-current extractions, myrcene was separated from linalool, with a purity of 91 mol% for myrcene in the vapor phase.
The recovery of metal resources from urban mines such as waste electrical and electronic equipment (WEEE) has become an emerging issue. The establishment of technology and social systems for recycling rare metals is of especially high priority due to their worldwide shortage. This study tackles the recycling of rare metals, especially tantalum, by applying a chain-using drum-type impact mill (CDIM) for pulverization of WEEE in the intermediate treatment for physical separation of components contained in plastic routers. A life-cycle assessment (LCA) was conducted based on actual process inventories of the CDIM, segregation and concentration of electronic parts. Climate change and resource depletion were adopted as the impact category indicated by life-cycle greenhouse gas emission (LC-GHG) and characterized resource consumption in this LCA. Although the tantalum contained in WEEE is input into the copper smelting and cannot be separated from other metals in conventional recycling systems, it was demonstrated that the CDIM intermediate treatment could selectively concentrate the tantalum capacitors. The tantalum capacitors can be converted into sintered tantalum, substitutes for Ta2O5, which can reduce resource consumption potentials at the expense of additional energy consumption. Most of the LC-GHG was derived from energy, especially public electricity. Decarbonization in the power grid can reduce the LC-GHG attributable to the recycling system. Rare metals other than tantalum should also be recoverable from WEEE. Physical and chemical treatment processes for metal recovery should be developed, demonstrated, and implemented in line with the recycling systems for various products.
To control the content of free CaO in the molten slag produced by municipal solid waste melting, experimental studies were conducted to quantify the dissolution of CaO particles into molten slag. The present work focused on the effect of Fe and Mg contents on the dissolution rate of CaO particles into simulated molten slags of CaO–SiO2–Al2O3 containing various amounts of FeO and MgO in the temperature range of 1673–1723 K. Results showed that, in comparison with FeO-free molten slag, the dissolution rate of CaO into molten slags containing FeO was significantly enhanced and was proportional to the FeO content. It was also shown that the presence of MgO in most cases enhanced the dissolution rate of CaO, but no appreciable relationship was observed between the dissolution rate and the MgO content. The apparent rate constant of dissolution of CaO particles into the molten slag was determined from the experimental data with the assumption that the mass transfer of CaO through molten slag film was the rate-determining step. It was found that the apparent rate constant of dissolution of CaO increased linearly with increasing FeO content. This apparent rate constant could be used to predict the time required for complete dissolution of CaO into actual molten slags.