Numerical modeling of multiphase fluid flow through the electrolytic cell

Electrolytic cells are used to obtain sodium hypochlorite (NaOCl), an important industrial product, from seawater. The chemical reaction of the process (NaCl + H2O → NaOCl + H2) produces hydrogen gas bubbles near the cathode\u27s surface inside a continuous liquid phase. In time, solid particles of calcium carbonate appear on the cell\u27s anode due to the cell operation. Thus, the fluid flow process in the cell, in general, is a three-phase process that includes turbulence. Although hydrogen bubbles and calcium carbonate particles are usually small in size, they aggregate in the system over time and lead to the blockage of the active area of the electrodes, which lowers the efficiency of the cell. It is important to understand where the regions with high concentration of hydrogen bubbles and solid particles inside the cell are located, and to design an optimally shaped electrolytic device. (Abstract shortened by UMI.)

Thermal transport eveluations related to waste package design -- model evaluations -- task 19

The purpose of the “Thermal Transport Evaluations Related to Waste Package Design” Task # 19 of Cooperative Agreement Number DE-FC28-98NV12081 was to develop a new CFDHT model for heat transfer and fluid flow in the potential rsepository at the Yucca Mountain, Nevada and to study the effects of forced convection during the pre-closure period and natural convection during the postclosure period. The analysis was performed for the drift dimensions shown in Figure 4-1 below. The intended use of the model is to estimate the velocity and temperature distribution as well as the highest temperature in the drift during the pre-closure and post-closure periods. The validation of the model is documented in section 6 of this report. The analysis was performed using both STAR-CD v. 3.150 and CFDHT v. 1.0, which are qualified software. The final result is the maximum temperature value in the drift during the pre-closure and post-closure period and the velocity and temperature distribution around the canisters

An improved numerical model for calculations of transport and size distributions of atmospheric aerosols and cloud droplets

Aerosols and cloud droplets in the atmosphere appear in different sizes. They can be transported by wind and experience various microphysical changes due to nucleation, collisional and condensational growth, evaporation and sedimentation. These microphysical processes affect optical properties of clouds and aerosols, and through it, they affect climate. Climate models usually lack a microphysical module, but instead use various parameterizations to represent clouds in the terrestrial atmosphere. Coupling between cloud microphysical models and climate models could improve the quality of numerical predictions of climate. In this study, CARMA (Community Aerosol and Radiation Model for Atmospheres), which is one of the best available microphysical models for calculation of size distributions of atmospheric aerosols and cloud droplets based on environmental conditions, has been redesigned and rewritten for coupling with numerical models of climate. In the revised model, data transfer between subroutines is handled via lists of arguments. The microphysical part of CARMA v. 2.2 was isolated from other processes, such as radiation and transport, and prepared for coupling with existing climate models. Changes were made to the vertical transport subroutines. The PPM (Piecewise Parabolic Method) method of solving the advection equation was replaced with the REA (Reconstruct-Evolve-Average) method, complemented with the minmod slope limiter. The sedimentation equation is now solved using the upwind method. Sedimentation fluxes, used by the upwind method, are calculated inside the microphysical part of CARMA. The ability of the revised CARMA model to reproduce the observed microstructure of a marine stratocumulus cloud over the North Sea was tested. The improved model closely reproduces most of the observed properties of the cloud and aerosols.M.S.Includes bibliographical references (p. 102-104)

Physical education classes with distance learning as a catalyst for adaptation potential increase of students during the COVID-19 pandemic

Physical education classes at all Russian universities are mandatory and held during the first, second and third years of studying for a bachelor’s degree. In connection with switching to distance learning during the COVID-19 pandemic, the investigated students of Kazan Federal University were engaged in both online physical education classes and self-study physical education classes with the obligatory keeping of a self-monitoring diary, which allowed tracking the dynamics of changes in psycho-emotional, functional states as well as physical fitness. As part of the educational process, teachers and students contacted through the Microsoft Teams platform, where classes and consultations were held; information and control materials were exchanged. A control group and an experimental group were formed with 90 students in each of the groups totalling 180 students. Each of the groups included 30 students of the main subgroup (healthy), 30 students of the preparatory subgroup (with minor deviations in health), and 30 students of the special medical subgroup with confirmed diseases of various nosology. In the control group, the students were engaged in physical education classes, fulfilling the general requirements: they filled out a self-monitoring diary, carried out the recommended tests to assess functional and physical fitness. Calculation of “working pulse rate” according to Karvonen’s formula gave students the opportunity to determine and select the amount and intensity of physical activity in the process of self-study. According to the self-monitoring diaries, the students showed positive dynamics in the psycho-emotional state. Students also noted the interdependence of their mood, well-being, desire to learn and be active on the quantity and quality of physical education classes. Exercises of sufficient intensity improved mood, relieved feelings of anxiety, and increased the positivity of perception of the surrounding environment. For ten weeks of distance learning, the students of the experimental group, whose physical activity was regulated individually, and the intensity of the load was selected with account of peculiarities of the work of their functional systems, showed a value of adaptation potential higher than that of students of the control group

Adaptation to physical activities by international students at a Russian University

The problem of adaptation by international students to studying at a Russian university was addressed. The conditions under which the physical education and physical activity classes at the University exert influence on adaptation of first-year international students were examined. The dynamics of the adaptation potential of first-year international students experiencing different types of motor activity while studying at a Russian university was investigated. The initial psycho-emotional state, physical and functional fitness of the international students before Semester 1 were measured and compared to those of first-year Russian students. It was concluded that initial adaptation reserves of the first-year international students were lower than those of the first-year Russian students. The international students were divided into four groups based on the level of their physical activity. It was found that the international students attending only mandatory physical education classes could adapt to a new cultural environment within one academic year, whereas the international students attending additional non-mandatory classes or sports clubs could accelerate their adaptation by half.Keywords: Physical Education; Sport; International students; Adaptation

Turbulent Flow Over a Backward-Facing Step Using Penalty and Equal-Order Finite Element Methods

Two-dimensional steady incompressible turbulent flow over a backward-facing step was calculated using equal-order and penalty function finite element methods. The standard k–ε turbulence model with wall functions was applied. Results from both of the methods for pressure-velocity coupling look similar to each other. The greatest discrepancy was observed for the velocity vector plots behind the step. While the equal order method showed physically correct behavior of velocity near the walls, the penalty function method gave oscillations for the velocity component parallel to the wall

Calculation of the Unsteady Gas Flow Around a Projectile Moving Through a Gun Barrel

The calculation of gas flow during the motion of a projectile in the gun barrel is a complicated computational task due of the presence of numerous factors, such as nonisothermicity, turbulence, changes in the shape of the computational domain with time, etc. In this study, an attempt to calculate the characteristics of gas flow around a projectile during the motion of the projectile in the gun barrel is undertaken. The flow is considered axisymmetrical, nonstationary, nonisothermal, compressible, and turbulent. For calculating the flow around the projectile, the finite volume method was employed. During the motion of the projectile, the flow pattern behind it changed from subsonic to supersonic. The results of the calculations are represented in figures depicting the flow at different moments of time. The figures show the fields of velocity, pressure and density, as well as the appearance of shock waves inside the gun barrel at subsonic and supersonic speeds

DEVELOPMENT OF AN ADVANCED HIGH TEMPERATURE HEAT EXCHANGER DESIGN FOR HYDROGEN PRODUCTION

ABSTRACT This paper deals with the development of an advanced high temperature heat exchanger design for hydrogen production by the sulfur iodine thermochemical cycle from advanced nuclear reactor concepts. The offset strip-fin hybrid plate type compact heat exchanger concept is chosen, and the material of manufacture is the liquid silicon impregnated carbon composite. The offset strip-fin is chosen as a method of heat transfer enhancement due to the boundary layer restart mechanism between the fins that has a direct effect on enhancing heat transfer. The effect of the fin thickness, pitch in flow direction, and the aspect ratio of the offset fins on the flow field and heat transfer are studied in 2-D using Computational Fluid Dynamics (CFD) techniques, and the results are then compared with the analytical calculation results. The preprocessor GAMBIT is used to create a computational mesh, and the CFD software package FLUENT, that is based on the finite volume method is used to produce numerical results. Proper dimensions of the strip fins need to be chosen in order to have an optimized heat transfer enhancement coupled with a reduced pressure drop. The study is conducted with helium gas as the working fluid with varied of Reynolds number values. The flow and heat transfer is considered to become periodically fully developed after a certain entrance length hence numerical simulations were performed using periodic boundary conditions. Two-dimensional numerical simulations were also performed for the whole length of the heat exchanger which has 37 such periodic modules. Comparison study was performed between the cases of fins with rectangular and curved geometry. Attempt has also been made in order to validate the coefficient of fin thickness (C fin ) value using CFD techniques, which has been used in the existing empirical correlations to suit this type of heat exchanger geometry. The model developed in this paper is used to investigate the heat exchanger design parameters in order to find an optimal design

Simulation of Multiphase Turbulent Fluid Flow Through an Electrolytic Cell

A Finite Volume Method was applied to a two-dimensional model for multiphase turbulent fluid flow inside an electrolytic cell. The model is based on solving the momentum equations for the single continuous liquid phase. In the model, solid particles and hydrogen gas bubbles are treated as inert spherical particles. Once the momentum equations are solved, trajectories of the particles can be calculated by integrating the force balance on the particle, which can be expressed in a Lagrangian reference frame. Turbulence is modeled via utilizing the standard k-ε model. The paper also discusses the computational meshes, which can be used for the simulation. It is shown that usage of the boundary layer type elements decreases the total number of computational nodes while maintaining the same accuracy in calculation. It is also shown that minute changes in the geometry of the cell, such as an increase in the thickness of the plate, results in obtaining more favorable flow patterns for taking solid particles away from the electrolytic cell