Search results for "Mass Transfer"
showing 10 items of 171 documents
Factors affecting the moisture permeability of lipid-based edible films: a review.
2002
Moisture transfers inside food products could be controlled or limited by the use of edible films. These are usually based on hydrophobic substances such as lipids to improve barrier efficiency. Water permeability of films is affected by many factors, depending on both the nature of barrier components, the film structure (homogeneous, emulsion, multilayer, etc.), crystal type, shape, size and distribution of lipids, and thermodynamics such as temperature, vapor pressure, or the physical state of water in contact to the films. After a brief presentation of lipids and hydrophobic substances used as moisture barrier, cited in the scientific literature, this article reviews all of the parameter…
Influence of impregnation solution viscosity and osmolarity on solute uptake during vacuum impregnation of apple cubes (var. Granny Smith)
2008
Vacuum-assisted impregnation of pectinmethylesterase (PME) solution has been recognized as an efficient pretreatment to improve the firmness of heat-treated fruit. In order to improve the control of solute infusion into fruit pieces, the effect of the osmolarity and viscosity of vacuum impregnation solution on solute penetration and distribution was studied in 1.5 cm apple cubes, using model PME-based solutions containing sodium chloride and/or sodium alginate. While vacuum impregnation of either a viscous hypotonic or a non-viscous hypertonic solution infused solutes homogeneously into fruit pieces, the penetration of viscous hypertonic solutions was much lower, and PME or chloride infusio…
Supported liquid membrane extraction of aromatic aminophosphonates
2001
Abstract A fast and efficient supported liquid membrane (SLM) extraction system for the series of substituted aromatic aminophosphonates was elaborated. The mass transfer of solute was examined in terms of operator (pH and ionic strength of water phase, composition of membrane phase and the concentration of analyte) dependent parameters. Additionally, the influence of the aminophosphonates structure on the extraction efficiency was examined. From the results it can be concluded that the most effective conditions of membrane process are 10% (w/w) carrier concentration (Aliquat 336) in the liquid membrane, high pH of donor phase (pH=11) and moderate salt concentration (0.4 M NaCl) in the acce…
From connected pathway flow to ganglion dynamics
2015
During imbibition, initially connected oil is displaced until it is trapped as immobile clusters. While initial and final states have been well described before, here we image the dynamic transient process in a sandstone rock using fast synchrotron-based X-ray computed microtomography. Wetting film swelling and subsequent snap off, at unusually high saturation, decreases nonwetting phase connectivity, which leads to nonwetting phase fragmentation into mobile ganglia, i.e., ganglion dynamics regime. We find that in addition to pressure-driven connected pathway flow, mass transfer in the oil phase also occurs by a sequence of correlated breakup and coalescence processes. For example, meniscus…
Solid-liquid mass transfer coefficients in gas-solid-liquid agitated vessels
1998
The research on mass transfer coefficients in solid-liquid agitated systems has received substantial attention in the past, due both to the interest in fundamental aspects of mass transfer between particles and turbulent fluids and to the importance of practical applications. In contrast, little information is available on solid-liquid mass transfer when a third gaseous phase is also dispersed into the system, in spite of the importance of the applications of gas-solid-liquid agitated systems. In this work a suitable dissolution technique was used to measure the solid-liquid mass transfer coefficient in gas-solid-liquid vessels stirred by either radial or axial impellers. The mechanical pow…
Rotating magnetic fields as a means to control the hydrodynamics and heat/mass transfer in the processes of bulk single crystal growth
1999
The report discusses the possibility of using different types of rotating magnetic fields (RMF) and combinations of these to control the hydrodynamics and heat/mass transfer in the processes of bulk semiconductor single crystal growth. Some factors contributing to the efficiency of RMF influence in different technologies are analysed. Their specific practical application is illustrated by some examples.
Mass/charge balance as a tool to estimate dimensional change in polypyrrole-based actuators
2006
The deconvolution of the voltammograms of polypyrrole electrochemistry has proved to be possible through the electrochemical quartz crystal microbalance data using the F(dm/dQ) function. This deconvolution allows the evolution of the thickness of the polypyrrole films during their redox processes to be estimated and therefore, the mechanical contraction/decontraction of this polymer as a function of the ionic exchange processes can be evaluated. Keywords: Polypyrrole, EQCM, Thickness change
Natural Convection Cooling of a Hot Vertical Wall Wet by a Falling Liquid Film
2008
Abstract The system studied is a plane channel in which one of the two vertical walls is kept at an arbitrary temperature profile and may be partially or completely wet by a falling liquid film, while the opposite wall is adiabatic. Air from the environment flows along the channel with a mass flow rate which depends on the balance between hydraulic resistances and buoyancy forces. These latter, in their turn, depend on the distribution of temperature and humidity (hence, density) along the channel and eventually on the heat and mass transferred from wall and film to the humid air. A simplified computational model of the above system was developed and applied to the prediction of relevant qu…
Ethyl Hexanoate Transfer Modeling in Carrageenan Matrices for Determination of Diffusion and Partition Properties.
2007
; Aroma compound properties in food matrices, such as volatility and diffusivity, have to be determined to understand the effect of composition and structure on aroma release and perception. This work illustrates the use of mass transfer modeling to identify diffusion and partition properties of ethyl hexanoate in water and in carrageenan matrices with various degrees of structure. The comparison of results obtained with a diffusive model to those obtained with a convective model highlights the importance of considering the appropriate transfer mechanism. Modeling of the preliminary experimental steps ensures correct estimation of the conditions for the main aroma release step. The obtaine…
New transport properties of ferrocolloids: magnetic Soret effect and thermomagnetoosmosis
2005
The paper deals with critical analysis of experiments on thermodiffusion in ferrocolloids. The observed magnetic Soret effect is significantly stronger than that predicted theoretically. It is shown that the main reason for that is the influence of a magnetic field on mass diffusion. Besides, some measurements are effected by uncontrolled thermal and solutal magnetic convection. Even in porous media, when macroscopic convection is depressed, thermodiffusion can be disturbed by microconvective mass transfer induced by particle magnetophoresis on filter grains.