Search results for "Mass Transfer"
showing 10 items of 171 documents
Applications of spray-drying in microencapsulation of food ingredients: An overview
2007
International audience; Spray-drying process has been used for decades to encapsulate food ingredients such as flavors, lipids, and carotenoids. During this drying process, the evaporation of solvent, that is most often water, is rapid and the entrapment of the interest compound occurs quasi-instantaneously. This required property imposes a strict screening of the encapsulating materials to be used in addition to an optimization of the operating conditions. Likewise, if the encapsulated compound is of hydrophobic nature, the stability of the feed emulsion before drying should also be considered. Thus, spray-drying microencapsulation process must rather be considered as an art than a science…
Heat and mass transfer analysis in single cell of PEFC using different PEM and GDL at higher temperature
2019
Abstract According to the H2 and fuel cell road map in Japan, the target operating temperature of polymer electrolyte fuel cell (PEFC) should be 90 °C from 2020 to 2025. In this study, the impact of polymer electrolyte membrane (PEM) and gas diffusion layer (GDL)'s thickness on heat and mass transfer characteristics as well as power generation performance of PEFC is investigated at operating temperature of 90 °C. The in-plane temperature distributions on anode and cathode separator are also measured using thermograph. As a result, it is observed that the increase in power from 1 W to 5 W at the current density of 0.80 A/cm2 as well as even temperature distribution within 1 °C can be obtaine…
How Electrical Heterogeneity Parameters of Ion-Exchange Membrane Surface Affect the Mass Transfer and Water Splitting Rate in Electrodialysis
2020
Electrodialysis (ED) has been demonstrated as an effective membrane method for desalination, concentration, and separation. Electroconvection (EC) is a phenomenon which can essentially increase the mass transfer rate and reduce the undesirable water splitting effect. Efforts by a number of researchers are ongoing to create conditions for developing EC, in particular, through the formation of electrical heterogeneity on the membrane surface. We attempt, for the first time, to optimize the parameters of surface electrical heterogeneity for ion-exchange membranes used in a laboratory ED cell. Thirteen different patterns on the surface of two Neosepta anion-exchange membranes, AMX and AMX-Sb, w…
Numerical modeling and validation of hydrothermal liquefaction of a lignin particle for biocrude production
2021
Abstract Lignin liquefaction process under catalyst-free conditions in a temperature range from 573 K to 647 K is investigated with this mathematical model. Based on the theoretical understanding of the physical and chemical processes of the liquefaction process in subcritical temperatures, a comprehensive mathematical model for the decomposition of lignin by hydrolysis reaction pathway is developed on the results of a series of batch experiments. The model consists of four main sections. They are liquefaction of lignin particle, oily film, and inorganic (ash) layer formation behavior during the liquefaction, kinetic model to model further liquefaction process of initial products, and the l…
Foam mat drying of yacon juice: Experimental analysis and computer simulation
2015
Abstract The foam mat drying of yacon juice (YJ) and concentrate yacon juice (CYJ) was conducted under various conditions of thickness of product (0.5, 1.0 and 1.5 cm) and air temperature (50, 60 and 70 °C). After drying the resulted dry powder was removed from the metallic tray and pulverized. Layer thickness and air temperature influenced statistically ( p > 0.5) drying time, moisture content and water activity (Aw) of the product. The shortest drying time to reach the desired Aw (0.1–0.3) corresponds to the condition of 0.5 cm and 70 °C for both juices – 59 and 65 min for the YJ and CYJ, respectively. The process was modeled in terms of heat and mass transfer and then simulated by a fin…
Development of a Gas Method for Migration Studies in Fractured and Porous Media.
1992
ABSTRACTA gas method for fast measurements of diffusion properties of porous materials has been developed. Diffusion coefficients in the gas phase are typically four orders of magnitude larger than those in the liquid phase. For samples whose structures do not change much upon drying it is possible to estimate the diffpision properties of the liquid phase when the properties of the gas phase are known. Advantages of the gas method are quick and easy measurements and therefore they can be used to optimize the liquid-phase measurements which may last months or years. For materials with good correlation between the gas and liquid-phase diffusion, the number of liquid phase measurements can be …
Influence of thermal process on structure and functional properties of emulsion-based edible films
2007
Abstract Synthetic food packaging is classically used to prevent mass transfer of various small molecules (water, gases, flavour compounds or solutes) between a food and its surrounding medium. In the case of composite foods, the development of edible films and coatings, applied between the different phases of this food is rising up. The increase of such food products shelf-life is indeed related to the barrier efficiency of these edible packaging against small molecules transfers. This is especially true for water transfer between compartments of different water activities in the same food, that leads to important physico-chemical changes and therefore to food quality deterioration. Film-f…
Drying of shrinking cylinder-shaped bodies
1998
Abstract A mathematical model has been developed for the prediction of sample temperature, average moisture and moisture distribution in a cylinder-shaped solid during the drying process. The effect of shrinkage was taken into account. The macroscopic heat balance and the microscopic mass balance combined with Fick's law were simultaneously solved using the Runge-Kutta-Merson method and a numerical finite difference method. The effective diffusion coefficient was expressed as a function of sample temperature and local moisture content. Using an experimental drying curve determined at 90 °C, the diffusional equation was identified for broccoli stems, and was used to predict the average and l…
NMR Studies of Single-File Diffusion in Unidimensional Channel Zeolites
1996
Single-file diffusion is the restricted propagation of particles that cannot pass each other. The occurrence of this phenomenon should be reflected by a change in the time dependence of the mean particle displacement in comparison with ordinary diffusion. Although this process is considered to be the rate-controlling mechanism in a large variety of processes, so far no direct evidence of this phenomenon has been provided. Diffusion measurements made with pulsed field gradient nuclear magnetic resonance (NMR) in unidimensional pore systems (zeolites AlPO4-5 and Theta-1) reflect the expected time dependence of single-file diffusion.
Magnetic field effect on the corrosion processes at the Eurofer–Pb–17Li flow interface
2015
Abstract Structural and elemental analyses of the RAFM steel (EUROFER 97) interface with flowing Pb–17Li eutectic (velocity 5 cm/s at 550 °C, 1000 h) under the action of a strong magnetic field (B = 1.7 T) were performed using optical microscopy, SEM, confocal microscopy, precision micro-hardness methods, SIMS and point or line-scan EDX analyses. The results show that the magnetic field induces a faster crushing of martensite into the grains, a deeper dissolution of grain boundaries, an enhancement of the Fe and Cr mass transfer and a fast detachment of corrosion layers due to MHD effects.