INVESTIGATION OF DISCRETE POPULATION BALANCE MODELS AND ITS PARAMETERS FOR TURBULENT EMULSIFICATION PRO- CESSES

Abstract. Different challenges and limitations occur with the simulation of liquid/liquid dispersion using population balance equations (PBE). A limitation is that the breakage and coalescence kernels tend to be specific to the equipment and scale used to acquire the evaluation data. It is reported in literature that PBE simulations are highly scale dependent. Once information is obtained using PBE, it cannot be used, with confidence, for scale-u

REMOVED: Process Intensification Through Micellar Enhanced Ultrafiltration

This article has been removed: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been removed at the request of the Executive Publisher.This article has been removed because it was published without the permission of the author(s)

Combined current and temperature mapping in an air-cooled, open-cathode polymer electrolyte fuel cell under steady-state and dynamic conditions

In situ diagnostic techniques provide a means of understanding the internal workings of fuel cells so that improved designs and operating regimes can be identified. Here, for the first time, a combined current density and temperature distributed measurement system is used to generate an electro-thermal performance map of an air-cooled, air-breathing polymer electrolyte fuel cell stack operating in an air/hydrogen cross-flow configuration. Analysis is performed in low- and high-current regimes and a complex relationship between localised current density, temperature and reactant supply is identified that describes the way in which the system enters limiting performance conditions. Spatiotemporal analysis was carried out to characterise transient operations in dead-ended anode/purge mode which revealed extensive current density and temperature gradients

Linear and nonlinear instability in vertical counter-current laminar gas-liquid flows

We consider the genesis and dynamics of interfacial instability in gas-liquid flows, using as a model the two-dimensional channel flow of a thin falling film sheared by counter-current gas. The methodology is linear stability theory (Orr-Sommerfeld analysis) together with direct numerical simulation of the two-phase flow in the case of nonlinear disturbances. We investigate the influence of three main flow parameters (density contrast between liquid and gas, film thickness, pressure drop applied to drive the gas stream) on the interfacial dynamics. Energy budget analyses based on the Orr-Sommerfeld theory reveal various coexisting unstable modes (interfacial, shear, internal) in the case of high density contrasts, which results in mode coalescence and mode competition, but only one dynamically relevant unstable internal mode for low density contrast. The same linear stability approach provides a quantitative prediction for the onset of (partial) liquid flow reversal in terms of the gas and liquid flow rates. A study of absolute and convective instability for low density contrast shows that the system is absolutely unstable for all but two narrow regions of the investigated parameter space. Direct numerical simulations of the same system (low density contrast) show that linear theory holds up remarkably well upon the onset of large-amplitude waves as well as the existence of weakly nonlinear waves. In comparison, for high density contrasts corresponding more closely to an air-water-type system, although the linear stability theory is successful at determining the most-dominant features in the interfacial wave dynamics at early-to-intermediate times, the short waves selected by the linear theory undergo secondary instability and the wave train is no longer regular but rather exhibits chaotic dynamics and eventually, wave overturning.Comment: 30 pages, 14 figure

Optimal permeate flux for an enzymatic oxidation of technical lignins in a membrane reactor

Enzyme membrane reactor systems (EMRS) offer a promising configuration for an enzymatic lignin modification/valorization by newly versatile peroxidases. This work continues in the same direction as our previous investigations using a 5-kDa tubular ceramic membrane for the fractionation of protein-ligninsulfonate model mixtures. Based on these preliminary studies, an in silico investigation is carried out for approximating the maximum product yield of an EMRS per operation cycle and membrane area. As a result, a permeate flux of 4 L mâ2 hâ1 was optimal for the 5-kDa membrane. In this context, a first assessment is given regarding fluid flow-related losses in versatile peroxidase activity