A new static mixer comprising multiple layers of stacked elements was developed for mixing fluids passing through a round pipe. The mixer with multi-stacked elements (MSE) provides complicated internal flow channels and enables sufficient stirring within a short distance. In this study, we investigated the pressure loss between the inlet and outlet of the mixer and the visualization of flow. Carboxymethyl cellulose with a fluorescent pigment was injected upstream through a nozzle inside a pipe, and water flow was monitored downstream with cross-sectional images produced using a green laser. Results showed the MSE exhibited a high pressure loss, which could be decreased by increasing the number of stacked elements. Analysis of the cross-sectional images obtained from the visualization experiments showed that MSE provided effective mixing. Suitable indexes are suggested for performing quantitative evaluation of mixing characteristics using such images.
A thermal swing continuous rotary regenerative CO2 adsorber employing a honeycomb rotor was experimentally studied. Based on a previous report, a honeycomb rotor binding 13X type zeolite, which has relatively high adsorption capacities for CO2, was prepared and mounted on a CO2 separation and recovery concentrator. Its performance was evaluated by measuring CO2 recovery concentration and recovery ratio. First, the existence of an optimal rotation speed for performance was confirmed. Next, a CO2 removal and recovery test was performed by changing feed gas conditions of humidity (dew point), temperature, and CO2 concentration, or by changing the main operation variable, regeneration temperature. As expected, performance improved as the dew point or temperature of feed gas was lower, and as regeneration temperature was higher. To attain a target performance of CO2 recovery ratio of 50% and CO2 concentration of 80% of recovered gas, it was found that feed gas required a dew point of ≤−20°C DP and temperature of ≤25°C at a regeneration temperature of 180°C. At a regeneration temperature was 160°C and a dew point of feed gas of ≤−60°C DP, a feed gas temperature around 35°C was acceptable for the above mentioned target performance. As the CO2 concentration of feed gas was increased, the CO2 recovery concentration increased, but recovery ratio decreased due to a relatively small increase of adsorption capacity. It was also found that the recovery gas flow rate should be set to an appropriate value by considering the relationship between recovery gas concentration, recovery ratio and feed gas concentration. Finally, on condition that regeneration temperature was 160°C or higher and the dew point of feed gas was ≤−20°C DP, the temperature of feed gas was found to largely affect the CO2 adsorption characteristics of a rotor. Therefore, lowering the temperature of feed gas should be given priority in order to reduce the energy requirement for regeneration and pre-dehumidification.
To raise the adsorption capacity of cation-exchange fiber for protein, two methods of pre-irradiation grafting using either a solution or an emulsion of glycidyl methacrylate (GMA) were compared. The epoxy group of poly-GMA grafted onto a commercially available 6-nylon fiber was converted into a sulfonic acid group by reaction with sodium sulfite. Lysozyme solution (pH 9.0) was passed through a bed charged with one of the cation-exchange fibers at a space velocity of 60 h−1. At a degree of GMA grafting of 81–87%, the 10% dynamic binding capacity of the bed charged with the fiber prepared by the emulsion grafting was four-fold that of the bed prepared by the solution grafting. The graft chain formed near the periphery of the fiber by the emulsion grafting is considered to contribute to the rapid capture of protein.
Substantial heat transfer enhancement is possible using a passage filled with a nanofluid-saturated metal foam, because of its high specific surface area, high thermal conductivity and comparatively low pressure drop. In addition to the Brownian diffusion and thermophoresis associated with nanofluids, both thermal dispersion and particle mechanical dispersion must also be fully understood in order to elucidate their combined effects on the heat transfer enhancement mechanism. Microscopic numerical calculations were conducted using a numerical model describing a structural unit of a passage filled with nanofluid-saturated metal foam. The results were integrated over a local control volume to evaluate the mechanical dispersion terms purely from the theoretical basis. The present study revealed that particle volume fraction has a limited effect on the thermal dispersion correlation, so that the correlations obtained for the base fluid are universally applicable. On the other hand, the nanoparticle mass flux was found to be sensitive to the interstitial heat transfer rate from the metal to nanofluid, since it increases with the interstitial heat transfer rate.
Thermo-physical properties of magnetic fluid (solvent: water, nanoparticulates: magnetite) were elucidated in order to examine their temperature dependency in both non-magnetic and vertical magnetic fields. The characteristics of heat transfer by natural convection were also investigated in non-magnetic and vertical magnetic fields in a horizontal enclosed rectangular container whose bottom plate was heated uniformly. The heat transfer of magnetic fluid in a horizontal enclosed rectangular container was found to decrease with increasing magnetic flux density, and this phenomenon was confirmed by thermal visualization using infrared thermography.
Understanding the behavior of complicated reactions is crucial to the design of efficient reaction processes in the chemical engineering field. Theoretical calculations now have greater ability to analyze individual reaction mechanisms and energies, but it is difficult to clarify the overall behavior of multiple reactions occurring in a system when multiple reactions involve the same substance. In this study, we developed new kinetics simulator that simultaneously calculates concentration changes of reactants and products in complicated reaction systems involving multiple reactions over various time scales. This simulator was applied to the results of theoretical calculations of CO2 gas absorption reaction by amine solution. It showed differences in product concentrations depending on the initial CO2 concentration.
Foot-and-mouth disease (FMD), a “specific domestic animal infectious disease,” needs biosecurity in the early stage but cannot be detected during the incubation period. This problem is dealt with by use of a detection agent and by immediate culling when the outbreak begins. However, developing a detection agent raises budgetary problems, and securing sites for culling and burial takes time. In this study, we adopted an epidemiological model known as the Keeling Model and developed a mathematical method to detect infected farms during the incubation period before clinical symptoms first appear. Our model based on the Keeling Model estimates the unobservable variate λ (the infection index), which indicates the situation of the susceptible farms with the observable variates of whether or not surrounding farms infected, the number and species of animals, and the distances between farms. In addition, we devised a model (Infection Estimating Model) and an estimation approach to estimate whether or not a farm is infected. The proposed method was applied to the case of FMD that occurred in Miyazaki Prefecture in 2010, and the validity of our proposal was confirmed. Moreover, as a result of an experiment to compare estimation accuracy, a universal factor was discovered that will improve estimation accuracy.
A cobalt-free humidity indicator (HDI) for silica gel was developed using tetraphenylporphyrin (Tpp), which showed a distinguishable color change depending on pH. The HDI was prepared by mixing dichloro(tetraphenylporphyrinato)phosphorus chloride (PTpp) and MgCl2 with SiO2 and drying at 130°C for 24 h. During the preparation, the PTpp was decomposed into the protonated Tpp (H2Tpp2+). The pH change arose from proton release by the reaction of MgCl2 with silanol of the SiO2 under dry conditions and neutralization under humid conditions. The HDI showed green color due to H2Tpp2+ under dry conditions and orange color due to Tpp under humid conditions. However, the HDI underwent partial decoloration on extended exposure to sunlight. Here, to prevent this decoloration, UV-absorbents coumarin and dibenzosuberenone were loaded onto the HDI. The HDIs with coumarin and without coumarin were irradiated at 352 nm and their microscopic absorption spectra were measured on a confocal laser scanning microscope. The absorbance at 650 nm and 515 nm of the HDI were monitored under dry and wet conditions, respectively. The light-protecting ability of UV-absorbent was analyzed by assuming that the decomposition process obeyed first-order kinetics. It was concluded that the additions of 0.125 wt% of coumarin and 0.050 wt% of dibenzosuberenone were effective to prevent decoloration of green color of H2Tpp2+ as well as orange color of Tpp.
With a view to controlling the melting point and extending the temperature range for practical application of calcium chloride hexahydrate as a latent heat storage material, an attempt was made to derive an empirical equation by which to evaluate quantitatively the degree to which various additives depress its melting point (measured value, 302 K). The change in melting point relative to the amount of additive was measured for each of nine additives, and the ability of each additive to depress melting point was expressed numerically by use of a simple empirical equation. Based on the assumption that the depression of melting point results from the synergistic action of completely dissociated ions in the melt, the ability of each type of ion was quantified, and the values were employed in a simple method to calculate the degree of melting point depression.