Search results for "mass [target]"
showing 10 items of 514 documents
Simplified dynamic pressure method for kLa measurement in aerated bioreactors
2010
Abstract A simplified version of the dynamic pressure method for measuring mass-transfer coefficients in gas–liquid systems is proposed. With this method oxygen concentration in the liquid phase is monitored after a sudden change of total pressure is applied to the system. With respect to the original technique introduced by Linek [14] the simplified version here proposed greatly simplifies the data treatment, yet resulting in good accuracy for most practical purposes. In practice, with the help of a simple mathematical model, it is found that the dynamic oxygen concentration response, when plotted as residual driving force versus time in a semi-log diagram, should be expected to finally se…
Unbaffled, Stirred Bioreactors for Animal Cell Cultivation
2017
One of the main features of animal cell bioreactors is that the cultured cells lack a strong membrane and are therefore more prone to shear damage. It is widely accepted that animal cell damage in aerated bioreactors is mainly related to burst bubbles at the air–liquid interface. A viable alternative to sparged bioreactors, aimed at minimizing cell damage, may be represented by uncovered, unbaffled, stirred tanks, which are able to provide sufficient mass transfer through the deep free surface vortex that takes place under agitation. As a consequence the need for bubble formation and subsequent bursting accompanied by cell damage is conveniently avoided. In this chapter, mass transfer perfo…
Gas-liquid-solid Operation of a High Aspect Ratio Self-ingesting Reactor
2012
Gas-liquid stirred vessels are widely employed to carry out chemical reactions involving a gas reagent and a liquid phase. The usual way for introducing the gas stream into the liquid phase is through suitable distributors placed below the impeller. An interesting alternative is that of using “self ingesting” vessels where the headspace gas phase is injected and dispersed into the vessel through suitable surface vortices. In this work the performance of a Long Draft Tube Self-ingesting Reactor (LDTSR) dealing with three-phase (gas-liquid-solid) systems, is investigated. Preliminary experimental results on the effectiveness of this contactor for particle suspension and gas-liquid mass transf…
Gas-liquid mass transfer rates in unbaffled tanks stirred by PBT: scale-up effects and pumping direction
2018
Abstract Unbaffled stirred tanks are increasingly recognized as a viable alternative to common baffled tanks for a range of applications such as biochemical, food or pharmaceutical processes where the presence of baffles is undesirable for some reason. In this work, the mass transfer performance of unbaffled stirred tanks with pitched blade turbine, operating either in up-pumping or down-pumping mode, was investigated. The influence of impeller size and liquid viscosity were also investigated. The mass transfer intensity was measured by means of the Simplified Dynamic Pressure. Method The measurements concerned both coalescent and non-coalescent (viscous) batches. Results confirm that incre…
Effect of the height-to-diameter ratio on the mass transfer and mixing performance of a biotrickling filter
2017
BACKGROUND Biotrickling filters (BTFs) are among the most widely used biological technologies for air pollution control. The pollutant removal rate in BTFs relies to a large extent on its gas–liquid mass transfer performance. Therefore, knowledge of the design parameters affecting the mass transfer and mixing performance of full-scale BTFs is of paramount importance. RESULTS This work showed that the height-to-diameter (H/D) ratio is an important parameter in the design of BTFs devoted to air pollution control. The H/D ratio significantly affected the mass transfer and mixing performance of the BTF with and without additional stirring in the holding tank. It was observed that under the same…
Mass transfer and hydrodinamic characteristics of a high aspect ratio self-ingesting reactor for gas-liquid operations
2007
Abstract The mass transfer performance of a gas–liquid self-ingesting stirred reactor is reported both for coalescing and non-coalescing systems. The vessel features are a high aspect ratio and a rather narrow multiple-impeller draft tube, through which the gas phase is ingested and led down to the vessel bottom, where it is finely dispersed into the liquid rising in the annular portion of the vessel. Comparison is made between k L a values determined by several variants of the dynamic method, among which pure oxygen absorption in a previously de-gassed liquid phase. Results show that the gas–liquid mass transfer coefficient values obtained with the last approach are remarkably larger than …
A Monge-Kantorovich mass transport problem for a discrete distance
2011
This paper is concerned with a Monge-Kantorovich mass transport problem in which in the transport cost we replace the Euclidean distance with a discrete distance. We fix the length of a step and the distance that measures the cost of the transport depends of the number of steps that is needed to transport the involved mass from its origin to its destination. For this problem we construct special Kantorovich potentials, and optimal transport plans via a nonlocal version of the PDE formulation given by Evans and Gangbo for the classical case with the Euclidean distance. We also study how these problems, when rescaling the step distance, approximate the classical problem. In particular we obta…
Mass Transport in Nanoporous Gold and Correlation with Surface Pores for EC 1 Mechanism: Case of Ascorbic Acid
2021
International audience; Entry for the Table of Contents Playing with the pores: Surface pores size in nanoporous gold modulates the electrode reactions pathways of ascorbic acid. The reaction is largely driven by diffusion when pores are smaller (nanometer). On the contrary, adsorption holds the key role when pores are bigger (micrometer), allowing permeation of molecules in the film volume.
A lap joint simulant laboratory test method of aluminium alloys
2015
A lap joint simulant cavity (LJSC) with a gap thickness of 200 μm has been developed to test corrosion of assembled coated aluminium alloys. The LJSC was instrumented with electrodes allowing simultaneous pH and potential measurements in 0.5 M NaCl solution. Assuming the outer part of the LJSC is electrochemically inactive (painted sheet) it was confirmed that in free corroding conditions the pH inside the LJSC tends more towards alkalinisation. On the opposite, if the outer part of the LJSC is electrochemically active (unpainted sheet) the pH inside the LJSC tends towards an acidic value.
Photoinduced mass transport in amorphous As‐S‐Se films
2012
Direct surface patterning due to photoinduced mass transport in amorphous As-S-Se films has been studied. Illumination of the films with two orthogonally (±45°) polarized beam interference pattern causes the formation of surface relief gratings on the films due to lateral mass transport regarding to light propagation direction. The obtained experimental results showed the dependence of photoinduced surface relief depth (Δh) on film thickness during holographic recording from film side as well as from glass substrate side. After constant exposure doses for the films with a thickness d 1 μm values of Δh do not depend significantly on the film thickness for recording from film side but decreas…