To improve the performance of an annular centrifugal contactor with high throughput and separation performance, the effect of operating conditions on fluidic and dispersion behavior was investigated by computational fluid dynamics (CFD) analysis based on the turbulence model, and the calculated results were validated by experimental data. The liquid phase in the annular zone was gradually divided into two regions vertically with increasing rotor speed and decreasing flow rate, and a liquid flow toward the center of the housing bottom was generated in the lower annular zone under all operating conditions. The droplet size of the dispersed phase in the annular zone decreased with increasing rotor speed and decreasing flow rate. These calculated results showed good agreement with the experimental data. CFD analysis taking into account mass transfer between aqueous and organic phases was also attempted, and it was confirmed that the change in extraction performance with rotor speed showed the same tendency as the experimental result.
In unsteady flows, the motion of the mixing pattern is apparently different from the motion of the fluid itself. If the fluid velocity field is the same, every initial mixing flow pattern finally tends to approach the same shape. From these facts, fluid flow fields are considered to have intrinsic mixing patterns, that is, potential mixing patterns. In this paper, a new velocity vector is defined that is able to express the motion of the mixing pattern. With this velocity vector, a method for visualizing potential mixing patterns is proposes, and several properties of these mixing patterns are shown clearly. Based on these results, a new conception of fluid mixing phenomena is proposed from a different point of view from the conventional ones.
LR500, an easily constructed new type of impeller, was developed for mixing highly viscous liquid, and its mixing performance was evaluated. LR500 showed stable operating characteristics with the same non-dimensional mixing time as a helical ribbon impeller and was able to mix highly viscous liquid of various liquid depths. In contrast, the helical ribbon impeller was not able to mix highly viscous liquid when the liquid depth was set at the position of the support bar, because an isolated, doughnut-shaped mixing region was generated in the vessel.
Process data of a commercial-scale batch distillation column for separation of a ternary mixture of 2-propanol/water/n-hexane was analyzed, and a simulation model capable of predicting dynamic conditions was developed. The developed model was applied to batch distillation in a commercial plant, and the operation performances were studied. By adjusting the conventional operating conditions, it was found possible to improve the function and performance of the process and achieve energy-saving.
The fundamental characteristics of a medical heat and moisture exchanger with filter (HMEF), the artificial nose, were investigated experimentally and numerically. Transient changes in the temperature and humidity in HMEF were measured. Saturated air at 37°C simulating exhalation by a patient was fed into the HMEF for 180 s, then dry air at 26°C simulating inhalation was fed in the opposite direction. CaCl2 installed in the HMEF intensified the condensation of water and retained water in the HMEF. The water vaporized in the returning dry air, allowing and a patient to inhale air with some humidity. The results also revealed that the condensed water can not be completely returned to the inhalation supply. The numerical results showed the difference in the process of condensation and vaporization.
A heat exchange system with two heat storage containers filled with phase change materials having different melting points was experimentally investigated to develop a cascaded heat storage system that allows the use of low-level thermal energy in an ambient temperature range. Lauric and myristic acids, which are harmless to the human body, were used as heat storage materials. The heat transport mechanisms involved in the melting and the solidification processes were analyzed by means of visualization and heat transfer experiments.
Technology employing melting point depression can be useful for extending the applicable temperature range of a latent heat storage material. In this study, the melting points Tm and latent heats of fusion ΔHf were measured in systems of disodium hydrogen phosphate dodecahydrate (with measured values of Tm,0=308.5 K and ΔHf,0=227 kJ/kg), which is especially utilized as a medical heat-retention material, with five additives that are readily soluble in the dodecahydrate melt: tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and sodium dihydrogen phosphate dihydrate. By using the simplified empirical formula proposed previously expressing the relation between additive concentration and the degree of melting point depression (Watanabe and Hirasawa, 2017) or the degree of latent heat decrease (Watanabe, 2017), the abilities of each additive to depress melting point and decrease latent heat were numerically expressed. These values differed from one additive to another and appeared to be specific to each. However, the numerical relation expressed in the equation below was found to hold almost invariably regardless of the additive