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Mass Transfer Properties (mass + transfer_property)
Selected AbstractsDIFFUSION OF BEET DYE DURING ELECTRICAL AND CONVENTIONAL HEATING AT STEADY-STATE TEMPERATURE,JOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2001MARYBETH LIMA ABSTRACT Ohmic heating has been shown to alter mass transfer properties of fruit and vegetable tissue. Diffusion of beet dye from beetroot tissue into a fluid was studied during conventional and ohmic heating as a function of steady-state temperature. The volume of beet dye diffusing into solution during ohmic heating was enhanced with respect to conventional heating at 42C and 58C, but not at 72C. This can be explained by examining the differences in electrical conductivity of beet tissue at these temperatures during conventional and ohmic heating. At 42 and 58C, the electrical conductivity of beet tissue heated ohmically is higher than the electrical conductivity of beet tissue heated conventionally. At 72C, the electrical conductivities of beet tissue during conventional and ohmic heating are equal. The extent of diffusion in the ohmic case is also positively correlated with applied voltage. These results suggest that food processes involving mass transfer can be enhanced by choosing conditions in which the electrical conductivity of a sample under ohmic conditions is maximized. [source] Effect of high-pressure food processing on the mass transfer properties of selected packaging materialsPACKAGING TECHNOLOGY AND SCIENCE, Issue 5 2010Maria Jose Galotto Abstract The effect of high-pressure processing (HPP) on the total migration into distilled water and olive oil and on the barrier properties of four complex packaging materials were evaluated. The films were polyethylene/ethylene-vinyl-alcohol/polyethylene (PE/EVOH/PE), metallized polyester/polyethylene, polyester/polyethylene (PET/PE), and polypropylene-SiOx (PPSiOx). Pouches made from these films were filled with food simulants, sealed and then processed at a pressure of 400,MPa for 30,min, at 20 or 60°C. Pouches kept at atmospheric pressure were used as controls. Prior to and after treatment, all films were evaluated for their barrier properties (oxygen transmission rate and water vapour transmission rate) and ,Total' migration into the two food simulants. In the case of water as the food stimulant, a low ,Total' migration was observed and even a lower one after the HPP treatment. In the case of oil as the food simulant, a higher ,Total' migration was found compared to the control as a result of damage to the structures during the HPP treatment. The gas permeability of the films increased after the HPP, compared to the control, due to damages in the structure caused during the treatment. The PET/PE film presented minimum changes in properties after HPP. Copyright © 2010 John Wiley & Sons, Ltd. [source] High-pressure processing effects on the mechanical, barrier and mass transfer properties of food packaging flexible structures: a critical reviewPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2004Cengiz Caner Abstract Food products can be high-pressure processed (HPP) either in bulk or prepackaged in flexible or semi-rigid packaging materials. In the latter case the packaging material is subjected, together with the food, to high-pressure treatment. A number of studies have been performed to quantify the effects of high-pressure processing on the physical and barrier properties of the packaging material, since the integrity of the package during and after processing is of paramount importance to the safety and quality of the food product. This article reviews the results of published research concerning the effect of HPP on packaging materials. Copyright © 2004 John Wiley & Sons, Ltd. [source] Hydrodynamic investigation of bubble-column reactors: effect of column configurationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010Abid Akhtar Abstract Bubble-column reactors are quite popular in the chemical, biochemical and petrochemical industries due to their relatively simple construction, favourable heat and mass transfer properties and low operating cost. Among the various design parameters, column geometry (configuration) has a significant impact on the overall throughput. In this study, an experimental investigation of the bubble-column configuration on its hydrodynamics has been conducted with three different sizes of the column (ID = 10,45 cm). A comparison in terms of the overall gas holdup as well as localised bubble properties is performed using the four-point optical technique and hydrodynamic similarities/dissimilarities are discussed. The study showed that the overall gas holdup was a function of the gas flow rate. For the range of gas velocity investigated (9.5,22.3 cm3/ min), the smaller column had 50,60% more holdup than the bigger column. Localised bubble properties exhibited similar behaviour (i.e. higher values for the smaller column). A comparative study of L/D illustrated an invariant behaviour at a high value of L/D (>5.5). A low L/D (,1.5), however, showed a prominent influence on hydrodynamics. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Numerical Simulation of Absorbing CO2 with Ionic LiquidsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2010X. Wang Abstract Although separating CO2 from flue gas with ionic liquids has been regarded as a new and effective method, the mass transfer properties of CO2 absorption in these solvents have not been researched. In this paper, a coupled computational fluid dynamic (CFD) model and population balance model (PBM) was applied to study the mass transfer properties for capturing CO2 with ionic liquids solvents. The numerical simulation was performed using the Fluent code. Considering the unique properties of ionic liquids, the Eulerian-Eulerian two-flow model with a new drag coefficient correlation was employed for the gas-liquid fluid dynamic simulation. The gas holdup, interfacial area, and bubble size distribution in the bubble column reactor were predicted. The mass transfer coefficients were estimated with Higbie's penetration model. Furthermore, the velocity field and pressure field in the reactor were also predicted in this paper. [source] The Influence of Differences Between Microchannels on Micro Reactor PerformanceCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2005E. R. Delsman Abstract Microstructured reactors most often contain a large number of micrometer-sized, parallel channels, instead of a large undivided reaction volume. Individual microchannels behave as plug-flow reactors without significant axial dispersion and with excellent heat and mass transfer properties. However, since the reaction takes place in a large number of parallel channels, it is important that all channels provide equal residence time and amount of catalyst volume. These issues depend not only on the flow distributor design, but also, for example, on the manufacturing tolerances. Correlations are derived to express the conversion of a multichannel microreactor explicitly as a function of the variance of a number of reactor parameters, viz. the channel flow rate, the channel diameter, the amount of catalyst in a channel, and the channel temperature. It is shown that the influence of flow maldistribution on the overall reactor conversion is relatively small, while the influences of variations in the channel diameter and the amount of catalyst coating are more pronounced. The model outcomes are also compared to experimental results of two microreactors with different catalyst distributions, which show that the presented method is able to provide a quick, though rough estimation of the influence of differences between channels on microreactor performance. [source] | ||||||||||