Numerical Investigation of Ohmic Heating in Channel Flow

Heat generation by direct electric conduction (ohmic heating) in a fully developed channel flow was studied to evaluate interaction between the hydrodynamic, electric and the thermal phenomena involved under the effect of natural convection. The equations governing the system were solved numerically by CFD finite volume code (FLUENT6.1 software package). The velocity profiles accelerate more near the wall than at the center that makes the temperature distribution uniform in the channel span. The numerical model is validated with an earlier experimental study [El Moctar et all. 1996] and yielded good agreement

Numerical modelling of mass transfer for solvent-carbon dioxide system at supercritical (miscible) conditions

A numerical procedure of mathematical model for mass transfer between a droplet of organic solvent and a compressed antisolvent is presented for conditions such that the two phases are fully miscible. The model is applicable to the supercritical antisolvent (SAS) method of particle formation. In this process, solute particles precipitate from an organic solution when sprayed into a compressed antisolvent continuum. Effects of operating temperature and pressure on droplet behavior were examined. The CO2 critical locus and the conditions for which the densities of solvent and carbon dioxide are equal are identified. Calculations were performed using Peng-Robinson equation of state. The model equations were put into the form that allowed the application of the Matlab standard solver pdepe. Calculations with toluene, ethanol, acetone (solvents) and carbon dioxide (antisolvent) demonstrated that droplets swell upon interdiffusion when the solvent is denser than the antisolvent and shrink when the antisolvent is denser. Diffusion modeling results might be used for data interpretation or experiments planning of the more complex real SAS process

Focusing of the flow capture for local exhaust ventilation systems

Through numerical modeling study the capacity of peripheral vortex shielding to generate the more concentrated exhaust inflow comparing with action of the conventional hood has been elucidated. Obtained data demonstrate evolution of focusing capture flow under variation of key parameters. Agreement between modeling results and observed flows has been revealed. The potential benefits of application of the vortex suction technique for local ventilation systems have been considered

Focusing of the flow capture for local exhaust ventilation systems

Through numerical modeling study the capacity of peripheral vortex shielding to generate the more concentrated exhaust inflow comparing with action of the conventional hood has been elucidated. Obtained data demonstrate evolution of focusing capture flow under variation of key parameters. Agreement between modeling results and observed flows has been revealed. The potential benefits of application of the vortex suction technique for local ventilation systems have been considered

Freezing time prediction for film packaged food

A freezing process of the film packaged slab-shaped food was studied by modeling and experimentally. Food samples temperature histories were determined by carrying out a freezing operation in an air-blast freezer. A freezing model was developed for an asymptotic case when film and food perform independently; thus, assuming the void between the food and the film are caused by appreciable food density change. Advanced model gives freezing time prediction that agrees reasonably well with the observed data

Micromechanics of perforation penetration and sand production in weak sandstone formations in Kazakhstan

Research on sand production has been conducted using different approaches: analytical, laboratory experiments including centrifuge tests, continuum based modeling and a more recent trend using discrete modeling

Self built of laboratory scale supercritical anti solvent system

Supercritical fluid (SCF) particles formation technique gained a significant attention mainly in the pharmaceutical, cosmetic and paints. However, the scarcity of information on the design and process for this type of laboratory scale equipment is a significant drawback to the technological progress. Therefore, the purpose of this study was to design and build a laboratory supercritical anti solvent (SAS) system for producing microparticles and microcapsules of acetaminophen. The operating conditions of the constructed system affected the yield. The optimum operating conditions were then determined as: 110 bars, 35° C, 35 mg/ml of polymer concentration and 1.75 ml/min of feed flow rate. The microparticles and microcapsules were characterized on its morphology (scanning electron microscopy), size distribution (particle size analyzer), thermal properties (thermo gravimetetric analyzer) and crystallographic (X-ray powder diffraction). The in vitro drug released of the microparticles and microcapsules were also investigated. The results revealed a more homogenous microparticle size distribution, a change in the crystalinity and maintained of drug thermal stability after the SAS process. Furthermore, the microcapsules prolong the drug released significantly in the in vitro study

Thermal conductivity of nanowires with boundary of different scattering types

International audienc

Thermal conductivity of nanowires with boundary of different scattering types

International audienc

Analytical description of phonon heat flow with diffusive boundary scattering

International audienceThe paper presents an analytical solution to the problem of heat flow due to the ballistic motion of phonons, which are diffusely reflected from the side walls of a two-dimensional dielectric material. An explicit analytical expression is obtained for the temperature profile in the approximation of linear dependence; explicit equations are derived for the heat flux and the thermal conductivity coefficients of the sample with arbitrary ratios of the width W and the length L. The analytical expressions are in very good agreement with numerical solutions of the integral equations, which describe these quantities and were derived in our previous study [J. Appl. Phys. 129, 085105 (2021)]. The obtained analytical relations can be used for subsequent studies in the case of mixed specular and diffuse reflection, as well as in the study of phonon systems of specific materials