Masakazu Enomura

Numerical simulation of fine droplets formation process in beadless disperser

SummariesThe deformation and breakup of a droplet in two-phase shear flow were simulated by the finite difference lattice Boltzmann method (FDLBM). The fine droplets formation process was investigated in a beadless disperser using ultrathin film and high shear (ultrathin film high-shear disperser, UFHD). As a result, the critical capillary number,Cac,was found at a constant Reynolds number,Re.The necessary condition for the creation of fine droplets in the disperser was that the capillary numberCa>Cac.The atomisation ability of the disperser was discussed based onCac.The simulation results demonstrated that the disperser can be used to prepare nanometre-size droplets.RésuméOn a simulé la déformation et la désintégration d’une gouttelette dans un écoulement de cisaillement à deux phases, grâce à la méthode de Boltzmann de treillis de différence finie (FDLBM). Le procédé de formation de gouttelettes fines a été investigué dans un disperseur beadless, en utilisant un film ultra mince et un [taux de] cisaillernent élevé (disperseur à film ultra mince et à taux de cisaillement élevé, UFHD). Comme résultat, le nombre capillaire critique,Cac,a été trouvé à un nombre de Reynolds constant,Re.La formation de gouttelettes fines dans le disperseur dépendait du fait que le nombre capillaireCa>Cac.Une discussion de la capacité d’atomisation du disperseur était basée surCac.Les résultats de la simulation ont montré que le disperseur peut être utilisé pour la préparation de gouttelettes de taille nanométrique.ZusammenfassungDie Verformung und Zerstörung eines Tropfens in Zwei-Phasen Scherfluss wurde mittels der Endlich-Differenz Lattice-Boltzmann Methode (finite difference lattice Boltzmann method, FDLBM) untersucht. Wir verwendeten einen kugellosen Disersator mit ultra-dünnem Film und großen Scherkräften (ultrathin film high-shear disperser, UFHD) um den Prozess der Tropfenbildung zu studieren und fanden, daß die kritische Kapillarnummer,Cac,einer konstanten ReynoldsnummerRe,entsprach. Für die Bildung feiner Tropfen im Dispersator war es nötig, daßCa>Cac.Wir diskutieren die Atomisierungsleistung des Dispersators auf der Basis vonCac.Die Ergebnisse unserer Simulation demonstrieren, daß der Dispersator zur Herstellung von Tropfen im Nanometerbereich verwendet werden kann.

Study of promotion of freeze-drying process by a blower using thermal edge flow

A blower using the thermal edge flow was proposed, which consists of thin plates in which there are several cuts and the one side of each cut is rounded, and one-way flow is realized. This blower was shown to promote the freeze-drying process in a low-pressure environment. Using a freeze-drying equipment which has a cold trap and heating plate that supplies the latent heat to materials, several sponge blocks and chemical powder were frozen and dried, and the drying time was shortened to almost a half by this blower.

A Study of Strong Shear Flow in a Narrow Gap of an Atomization Equipment

The mechanism of solid particle atomization by strong shear flow inside a narrow gap between a still disk and a rapidly rotating disk of a new beadless disperser called SS5 is clarified. We show that the solid particles rotate at the same rate as fluid particles, that is the angular velocity is a half of the vorticity using a equipment consisting of a rotating cylinder inside a cylindrical vessel, instead of rotating disks. The cavitation is shown to occur inside the gap and the mechanism of atomization of solid particles is considered to be due to the cavitation collapse. The cavitation generation is also considered to be promoted by the rapid rotation of the particles due to the strong shear and also by the pressure drop due to the centrifugal force driven by the rotation of the disk.Copyright

A Study of Promotion of Sublimation Phenomenon of Freeze Drying by Using Thermal Edge Flow

A blower driven by the thermal edge flow was shown to be possible to use for freeze drying. First, the pressure rise by the thermal edge flow was confirmed by using an accumulation unit. The pressure rise of 5Pa was given. Next, the effect of the blower for sublimation from frozen material was confirmed by using frozen sponges containing some water. The necessary time for drying by using the blower was roughly half compared with a drying time by not using the blower and the effect of the blower for sublimation depended on the surrounding vacuum pressure.Copyright