Setsuro Hiraoka

Power Consumption and Mixing Time in an Agitated Vessel with Double Impeller

Power consumption in a non-baffled agitated vessel with a double impeller was measured over a wide range of Reynolds number from laminar to turbulent flow regions. The power correlation for the double impeller was derived from the modification of the power correlation for a single impeller proposed by the authors. The power consumption in a baffled vessel was only measured in the turbulent flow region. The power consumption for the double impeller has the maximum value, which was almost twice the power consumption for the single impeller at larger ratio of impeller clearance to liquid depth than 0.35, and it took the minimum value at the impeller clearance ratio of 0.18–0.25. Mixing time in a baffled vessel with some types of double impeller was measured in the turbulent flow region using the decolorization method of sodium thiosulfate and iodine reaction. The minimum mixing time was observed at 0.1–0.2 of the ratio of impeller clearance to liquid depth for the two-stage paddle system, and 0.5–0.7 for the double impellers constructed with the pitched blade paddle. The relationship of mixing time to power consumption for the double impeller system coincided with that for a single impeller at the impeller clearance taking the minimum mixing time.

TURBULENT FLUIDIZATION PHENOMENA

ABSTRACT Based on the observed vertical profile of average pressure in the bed and FFT analysis of its fluctuation, new criteria are proposed to distinguish higher gas velocity fluidization into different fluidization regimes; such as, slugging, transient, turbulent and dilute phase regime. To determine these fluidized regimes approximately from the measurement of pressure fluctuation in the bed, a simple method is also proposed. Observed data of transition Rep between each regime measured under both atmospheric and high pressure conditions can be correlated well as function of Ar. Effects of operating conditions upon the voidage in the turbulent fluidized bed and in its freeboard are also briefly discussed.

Enhanced anthocyanin production from grape callus in an air-lift type bioreactor using a viscous additive-supplemented medium.

An N-medium containing carboxymethyl cellulose (CMC) was applied to an air-lift type bioreactor culture of grape (Vitis vinifera cv. Bailey alicant A.) callus, and anthocyanin production was investigated. Grape callus grew well at an air flow rate of 80 ml/min and anthocyanin production was significantly increased in the N-medium, reaching 17 mg/l after 7 d of culture. The anthocyanin content of the N-medium was about two times higher than that of the conventional medium without CMC. The effect of air flow rate was also investigated within the range from 40 to 160 ml/min. A twofold increase in anthocyanin content was obtained at all the air flow rates tested in the N-medium. The distribution of grape callus size obtained after 7 d of the bioreactor culture was investigated. The average callus size was 490 mum which was 1.6 times larger than that obtained in the conventional medium. It was found that large calli with a relatively high anthocyanin pigment content were formed in the bioreactor culture using the N-medium. The fluid dynamics in the bioreactor was also investigated at three points (top, middle and bottom) in the bioreactor by laser doppler velocimetry. The average axial velocity of the circulated medium was 0.4 times lower than that of the conventional medium while their average radial velocities were almost the same (zero). The standard deviation of radial velocity fluctuation in the N-medium was also 0.4 times less than that in the conventional medium. These results suggest that turbulent flow occurred in the bioreactor culture using the conventional medium and the degree of turbulent flow decreased significantly when 0.8% CMC was added to the medium to prepare the N-medium. A change of the flow pattern is considered to be the cause of the decrease in hydrodynamic stress, resulting in enhanced pigment production due to the enlargement of the callus.

Performance of a shaking vessel-type bioreactor with a current pole

The performance of a shaking vessel-type bioreactor with a current pole at its central axis was examined experimentally with respect to particle dispersion, power consumption, and solid-liquid mass transfer coefficient. The current pole improved the particle dispersion without an increase in power consumption and reduced the critical circulating frequency for complete suspension. The mass transfer coefficient with a current pole had the same value as that without a current pole above the critical circulating frequency for complete suspension. The shaking vessel-type bioreactor with a current pole was thus very suitable for the mass production of regenerated plantlets from fragmented horseradish hairy roots.

Mass transfer and shear stress on a vertical electrode with gas evolution

Abstract The relationship between the mass transfer coefficient and the shear stress along the vertical electrode was investigated under electrolytic gas evolution, either oxygen or hydrogen, from alkaline solution containing ferrocyanide and ferricyanide ions. The shear rate obtained from the shear stress measurement was empirically correlated with the gas evolving current density, the electrode height and the liquid kinematic viscosity. The dimensionless correlation of the mass transfer coefficient with the shear stress under oxygen evolution condition agreed formally with the correlation of the mass transfer in turbulent-free convection. On the other hand, the experimental results under hydrogen evolution varied greatly from those under oxygen evolution.

Mixing Properties of Unsymmetrical Molten Salts Based on the Law of Corresponding States

The law of corresponding states of molten salt mixtures that include unsymmetrical salts was developed. The corresponding states equations for the thermodynamic and transport properties were obtained by expanding the Helmholtz free energy and the transport properties in terms of differences of the pair potential parameters, difference of the ionic size, and difference of the ionic mass. The effect of valences on the properties was accounted for by the products of cation and anion valences in the corresponding states equations. Equations for the mixing molar volume, surface tension, electrical conductivity, and viscosity were derived from the corresponding states equations. The estimated mixing properties satisfactorily agreed with the observed ones.

Plate-to-plate calculation method for reacting distillation and application of Lyster's method to operational problems.

効率を考慮した反応蒸留問題の逐次段計算法が提案された.これまでいくつかの反応蒸留に関する数値解法が報告されてきたが, いずれも理想段を仮定しており, その分離への影響は考慮されていなかった.本解法では逐次段計算に反応と段効率を導入し, Plate-matchingの条件を満足させるためのLysterのθ法と組み合わせることにより操作型反応蒸留問題の厳密と迅速解を得ることに成功した.本報では, 数値計算例によって, 本解法の収束特性および初期値に対する安定性が示され, この有用性が実証された.