The purpose of this study was the coupling simulation of the vacuum block of the ethanolamine mixture separation unit to determine the optimal layout of the vacuum creation system. For this, a computational model of the vacuum unit, which was identified by comparing the computational data with the data of an industrial study of vacuum rectification columns, was synthesized in the Unisim Design R461 software package. To determine the required load on the vacuum system, a numerical experiment was carried out, during which it was discovered that the load on the system would be 9600 m3/h. It was proposed to replace individual column vacuum pumps with a single vacuum-generating system (VGS) based on a liquid ring vacuum pump (LRVP). When defining the layout, two possible schemes were considered, the models of which were created in Unisim Design R461. The system layout was determined by matching the characteristics of the system elements with the characteristics of the vacuum columns. A tech... [more]

Capacitor discharge welding (CDW) for projection welding provides very high current pulses in extremely short welding times. This requires a quick follow up behaviour of the electrodes during the softening of the projection. The possibilities of experimental process investigations are strongly limited because of the covered contact zone and short process times. The Finite Element Method (FEM) allows highly resoluted analyses in time and space and is therefore a suitable tool for process characterization and optimization. To utilize this mean of optimization, an indirect multiphysical numerical model has been developed in Ansys Mechanical APDL. This model couples the physical environments of thermal−electric with structural analysis. It can master the complexity of large deformations, short current rise times and high temperature gradients. A typical ring projection has been chosen as the joining task. The selected aluminium alloys are EN-AW-6082 (ring projection) and EN-AW-5083 (sheet... [more]

Compression ignition (CI) engines that run on high-viscosity fuels (HVF) like emulsified biofuels generally demonstrate poor engine performance. An engine with a consistently low performance, in the long run, will have a negative effect on its lifespan. Poor combustion in engines occurs mainly due to the production of less volatile, less flammable, denser, and heavier molecules of HVF during injection. This paper proposes a guide vane design (GVD) to be installed at the intake manifold, which is incorporated with a shallow depth re-entrance combustion chamber (SCC) piston. This minor modification will be advantageous in improving the evaporation, diffusion, and combustion processes in the engine to further enhance its performance. The CAD models of the GVD and SCC piston were designed using SolidWorks 2018 while the flow run analysis of the cold flow CI engine was conducted using ANSYS Fluent Version 15. In this study, five designs of the GVD with varying lengths of the vanes from 0.6D... [more]

The novel coronavirus disease (COVID-19) poses a severe threat to public health officials all around the world. The early COVID-19 outbreak in South Korea displayed significant spatial heterogeneity. The number of confirmed cases increased rapidly in the Daegu and Gyeongbuk (epicenter), whereas the spread was much slower in the rest of Korea. A two-patch mathematical model with a mobility matrix is developed to capture this significant spatial heterogeneity of COVID-19 outbreaks from 18 February to 24 March 2020. The mobility matrix is taken from the movement data provided by the Korea Transport Institute (KOTI). Some of the essential patch-specific parameters are estimated through cumulative confirmed cases, including the transmission rates and the basic reproduction numbers (local and global). Our simulations show that travel restrictions between the epicenter and the rest of Korea effectively prevented massive outbreaks in the rest of Korea. Furthermore, we explore the effectiveness... [more]

Natural convection in cavities is an interesting subject for many researchers. Especially, in recent years, the number of articles written in this regard has grown enormously. This work provides a review of recent natural convection studies. At first, experimental studies were reviewed and, then, numerical studies were examined. Then, the articles were classified based on effective parameters. In each section, numerical studies were examined the parameters added to the cavity such as magnetic forces, fin, porous media and cavity angles. Moreover, studies on non-rectangular cavities were investigated. Free convection in enclosures depends more on the fluid velocity relative to the forced convection, leading to the opposite effect of some parameters that should essentially enhance rate of heat transfer. Nanoparticle addition, magnetic fields, fins, and porous media may increase forced convection. However, they can reduce free convection due to the reduction in fluid velocity. Thus, these... [more]

Dengue fever has been a threat to public health not only in tropical regions but non-tropical regions due to recent climate change. Motivated by a recent dengue outbreak in Japan, we develop a two-patch model for dengue transmission associated with temperature-dependent parameters. The two patches represent a park area where mosquitoes prevail and a residential area where people live. Based on climate change scenarios, we investigate the dengue transmission dynamics between the patches. We employ an optimal control method to implement proper control measures in the two-patch model. We find that blockage between two patches for a short-term period is effective in a certain degree for the disease control, but to obtain a significant control effect of the disease, a long-term blockage should be implemented. Moreover, the control strategies such as vector control and transmission control are very effective, if they are implemented right before the summer outbreak. We also investigate the c... [more]

In industrial processes, a semi-cavity area formed by airflow wherein the particles circulate is called a “raceway”. In a blast furnace, the role of the raceway is particularly important. To understand and predict the evolution and physical characteristics of the raceway, a three-dimensional transient Eulerian multiphase flow model in a packed particle bed was developed. In the model, it was assumed that the gas and solid (particle) phases constitute an interpenetrating continuum. The gas-phase turbulence was described as a k−ε dispersed model. The gas-phase stress was considered in terms of the effective viscosity of the gas. The solid-phase constitutive relationship was expressed in terms of solid stress. It was found that the evolution process of the raceway can be divided into three stages: (1) rapid expansion, (2) slow contraction, and (3) gradual stabilization. When the blast velocity was increased from 150 m/s to 300 m/s, the surface area of the raceway increased from 0.194 m2 t... [more]

In the arid west, the freshwater supply of many communities is limited, leading to increased interest in tapping brackish water resources. Although reverse osmosis is the most common technology to upgrade saline waters, there is also interest in developing and improving alternative technologies. Here we focus on membrane capacitive deionization (MCDI), which has attracted broad attention as a portable and energy-efficient desalination technology. In this study, a fully coupled two-dimensional MCDI process model capable of capturing transient ion transport and adsorption behaviors was developed to explore the function of the ion-exchange membrane (IEM) and detect MCDI influencing factors via sensitivity analysis. The IEM enhanced desalination by improving the counter-ions’ flux and increased adsorption in electrodes by encouraging retention of ions in electrode macropores. An optimized cycle time was proposed with maximal salt removal efficiency. The usage of the IEM, high applied volta... [more]

Based on the shear stress transport (SST) turbulence model, the influence of different outlet pipe angles on the head and efficiency of a boiler circulating pump was analyzed. When the outlet pipe angle changed from 115° to 130°, the head and efficiency of the pump reduced significantly. The boiler circulating pump with 115° outlet pipe angle was selected as the further research object, and the reliability of the numerical simulation was verified by experiments. The transient flow of the prototype pump under the design flow rate condition (1.0Qd) and four other flow rate conditions (0.6Qd, 0.8Qd, 1.2Qd, and 1.4Qd) was studied. The results show that, under the conditions of design flow and large flow rate (1.0Qd, 1.2Qd, and 1.4Qd), the centrality and regularity of radial force distribution are obviously better than those of small flow rate (0.6Qd, 0.8Qd). The leakage of the rear seal ring is less than that of the front seal ring under five flow rate conditions. As the flow rate increase... [more]

Coal-fired industrial boilers should operate across a wide range of loads and with a higher reduction of pollutant emission in China. In order to achieve these tasks, a physical model including two swirling burners on the front wall and boiler furnace was established for a 35 t/h pulverized coal-fired boiler. Based on Computational Fluid Dynamics (CFD) theory and the commercial software ANSYS Fluent, mathematical modeling was used to simulate the flow and combustion processes under 75% and 60% load operating conditions. The combustion characteristics in the furnace were obtained. The flue gas temperature simulation results were in good agreement with experimental data. The simulation results showed that there was a critical distance L along the direction of the furnace depth (x) and Hc along the direction of the furnace height (y) on the burner axis. When x < L, the concentration of NO decreased sharply as the height increased. When y < Hc, the NO concentration decreased sharply... [more]

This is a collection of Aspen Plus v8.8 Simulation Files that were used to conduct the research published in Dalle Ave G, Adams TA II, "Techno-economic comparison of Acetone-Butanol-Ethanol fermentation using various extractants", Energy Conversion and Management, Volume 156, 15 January 2018, Pages 288-300. The LAPSE postprint of this work is available at LAPSE:2018.0132.

Each simulation file contains a flowsheet model of the process to recover acetone, butanol, and ethanol from the ABE fermentation broth for the following case studies:

1. Direct distillation of the ABE Broth
2. Product extraction and purification from ABE Broth using 2-Ethyl-1-Hexanol
3. Product extraction and purification from ABE Broth using Decane
4. Product extraction and purification from ABE Broth using Decanol
5. Product extraction and purification from ABE Broth using Hexanol
6. Product extraction and purification from ABE Broth using Mesitylene
7. Product extraction and purification from ABE... [more]

Flow distribution channels in extrusion dies are typically designed to assure uniform fluid velocity, pressure and temperature in the outlets. To ensure this uniformity, it is desirable to have the fluid melt to reach a steady state temperature in the entrance channel before entering the die body. This paper numerically investigates the temperature distribution of the fluid melt in the entrance channel. Analytical solutions of the velocity and finite element solutions of temperature distribution in Poiseuille flows of polypropylene melt with the Casson rheology model were derived and presented. In the velocity solution, the critical point that separates the core and the remaining parts in the flow was calculated by using the inlet flow rate and the yield stress in the Casson model. The velocity distribution was then substituted into the convective heat equation for temperature distribution simulations. A finite difference scheme was used to obtain the temperature distribution profiles... [more]

The Discrete Element Method has been widely used to simulate geo-materials due to time and scale limitations met in the field and laboratories. While cohesionless geo-materials were the focus of many previous studies, the deformation of cohesive geo-materials in 3D remained poorly characterized. Here, we aimed to generate a range of numerical ‘sediments’, assess their mechanical response to stress and compare their response with laboratory tests, focusing on differences between the micro- and macro-material properties. We simulated two endmembers—clay (cohesive) and sand (cohesionless). The materials were tested in a 3D triaxial numerical setup, under different simulated burial stresses and consolidation states. Variations in particle contact or individual bond strengths generate first order influence on the stress−strain response, i.e., a different deformation style of the numerical sand or clay. Increased burial depth generates a second order influence, elevating peak shear strength.... [more]

Two types of stall patterns in the centrifugal compressor with a wide vaneless diffuser were numerically studied in this paper. We carried out kinds of three-dimensional numerical simulations of the instability process in wide vaneless diffusers with different radius ratios. The results show that there are two kinds of stall patterns in wide vaneless diffusers with different radius ratios. For a short diffuser with a radius ratio of 1.5, the speed of the propagation of stalled cells is relatively high, and the propagation speed and frequency of stall cells do not change with the decrease in the flow rate. For a long diffuser with a radius ratio of 1.8, the propagation velocity of stall cells is smaller to the one in the short diffuser, and increases with the decrease in flow rate. For wide vaneless diffusers with different radius ratios, the main factor causing stall is the outlet reflux. Reducing the radius ratio of the wide vaneless diffuser has an important influence on the stabilit... [more]

Oscillatory baffled reactors (OBRs) have attracted much attention from researchers and industries alike due to their proven advantages in mixing, scale-up, and cost-effectiveness over conventional stirred tank reactors (STRs). This study quantitatively investigated how different mixing indices describe the mixing performance of a moving baffle OBR using computational fluid dynamics (CFD). In addition, the hydrodynamic behavior of the reactor was studied, considering parameters such as the Q-criterion, shear strain rate, and velocity vector. A modification of the Q-criterion showed advantages over the original Q-criterion in determination of the vortices’ locations. The dynamic mesh tool was utilized to simulate the moving baffles through ANSYS/Fluent. The mixing indices studied were the velocity ratio, turbulent length scale, turbulent time scale, mixing time, and axial dispersion coefficient. We found that the oscillation amplitude had the most significant impact on these indices. In... [more]

The paper concerns the modeling of heterogeneous biofilm growth on fine spherical particles of such biofilm forms as, e.g., fluidized-bed bioreactors. Three discrete mathematical models based on cellular automata theory were proposed. The double-substrate kinetics of biomass growth, biomass displacement, internal and external mass transfer resistances, death and lysis of microbiological cells and biofilm detachment were taken into account. It was shown that there are no significant qualitative and quantitative differences between biofilm growth on flat and spherical particles of different radii. Computer simulations were compared with experimental observations. Qualitative and quantitative agreement areachieved if both cell death and lysis aretaken into consideration and a proper algorithm of biomass displacement is used. The value of the bacteria lysis rate coefficient was estimated.

A two-dimensional (2D) Computational Fluid Dynamics (CFD) scale-up model of the Fischer Tropsch reactor was developed to thermally compare the Microfibrous-Entrapped-Cobalt-Catalyst (MFECC) and the conventional Packed Bed Reactor (PBR). The model implements an advanced predictive detailed kinetic model to study the effect of a thermal runaway on C5+ hydrocarbon product selectivity. Results demonstrate the superior capability of the MFECC bed in mitigating hotspot formation due to its ultra-high thermal conductivity. Furthermore, a process intensification study for radial scale-up of the reactor bed from 15 mm internal diameter (ID) to 102 mm ID demonstrated that large tube diameters in PBR lead to temperature runaway >200 K corresponding to >90% CO conversion at 100% methane selectivity, which is highly undesirable. While the MFECC bed hotspot temperature corresponded to 30% CO conversion, attributing to significantly high thermal conductivity of the MFECC bed. Moreover, a noticeable i... [more]

The hydration layer has a significant effect on the adsorption behavior of reagents during the flotation process of low-rank coal. Understanding the effect of hydration layer on the adsorption of common collectors on low-rank coal is a prerequisite for proposing a new enhanced coal floatation method. In this study, a smooth low-rank coal surface model with a density of 1.2 g/cm3 was constructed and compared with the XPS results. Three different systems, coal-water, coal-collector, and coal-water-collector, were constructed. Molecular dynamics method was applied to study the adsorption behaviors of water and dodecane molecules. Simulation results revealed that a stable hydration layer with a thickness of about 5 Å was formed due to the strong attraction of coal surface. The negative value of interaction energy (IE) indicated that dodecane molecules could spontaneously adsorb on the coal surface. Dodecane molecules were successfully adsorbed on the coal surface when it was located inside... [more]

Pump as turbines (PATs) are widely applied for recovering the dissipated energy of high-pressure fluids in several hydraulic energy resources. When a centrifugal pump operates as turbine, the large axial vortex occurs usually within the impeller flow passages. In view of the structure and evolution of the vortex, and its effect on pressure fluctuation and energy conversion of the machine, a PAT with specific-speed 9.1 was analyzed based on detached eddy simulation (DES), and the results showed that vortices generated at the impeller inlet region, and the size and position of detected vortices, were fixed as the impeller rotated. However, the swirling strength of vortex cores changed periodically with double rotational frequency. The influence of vortices on pressure fluctuation of PAT was relatively obvious, deteriorating the operating stability of the machine evidently. In addition, the power loss near impeller inlet region was obviously heavy as the impact of large axial vortices, wh... [more]

Here, a study for MHD (magnetohydrodynamic) impacts on the rotating flow of Casson Carreau nanofluids is considered. The temperature distribution is associated with thermophoresis, Brownian motion, and heat source. The diffusion of chemically reactive specie is investigated with Arrhenius activation energy. The governing equations in the 3D form are changed into dimensionless two-dimensional form with the implementation of suitable scaling transformations. The Variational finite element procedure is harnessed and coded in Matlab script to obtain the numerical solution of the coupled non-linear partial differential problem. The variation patterns of Sherwood number, Nusselt number, skin friction coefficients, velocities, concentration, and temperature functions are computed to reveal the physical nature of this examination. It is seen that higher contributions of the magnetic force, Casson fluid, and rotational fluid parameters cause a raise in the temperature like thermophoresis and Br... [more]

Desalination has become one of the obvious solutions for the global water crisis due to affording high-quality water from seawater and brackish water resources. As a result, there are continuing efforts being made to improve desalination technologies, especially the one producing high-quantity freshwater, i.e., thermal desalination. This improvement must be accomplished via enhancement of process design through optimization which is implicitly dependent on providing a generic process model. Due to the scarcity of a comprehensive review paper for modeling multi-effect distillation (MED) process, this topic is becoming more important. Therefore, this paper intends to capture the evolution of modeling the forward feed MED (most common type) and shed a light on its branches of steady-state and dynamic modeling. The maturity of the models developed for MED will be thoroughly reviewed to clarify the general efforts made highlighting the advantages and disadvantages. Depending on the outputs... [more]

Mechanical flow and segregation phenomena within a bed composed of milli-metric size spherical beads rotated in a horizontal drum were investigated. The beads population was bi-dispersed, with two kinds of binary (half by half) compositions: a bi-size bed with two different sizes and a bi-density bed with two different densities. The distributions of the beads were observed optically on the front side of the bed by means of a lab-scale drum prototype. Different numbers and lengths of peripheral straight baffles were tested as well as different drum filling ratios. The photographical data were processed to obtain the front layer mechanical segregation index. This experimental index was compared to the simulated one, obtained by means of commercial discrete element software EDEM. The simulations were corroborated by the experiments provided that the friction coefficients of the discrete elements method (DEM) model were correctly adjusted. The global segregation index was also calculated... [more]

Screening techniques have been widely deployed in industrial production for the size-separation of granular materials such as coal. The elliptical vibrating screen has been regarded as an excellent screening apparatus in terms of its high screening efficiency and large processing capacity. However, its fundamental mechanisms and operational principles remain poorly understood. In this paper, the sieving process of an elliptical vibrating screen was numerically simulated based on the discrete element method (DEM), and an approach coupling the DEM and the finite element method (DEM−FEM) was introduced to further explore the collision impact of materials on the screen deck. The screening time, screening efficiency, maximum stress and maximum deformation were examined for the evaluation of sieving performance. The effects of six parameters—length of the semi-major axis, length ratio between two semi-axes, vibration frequency, inclination angle, vibration direction angle and vibration direc... [more]

Graphene nanofluids have attracted the attention of many researchers because of a variety of remarkable properties such as extraordinary electronic transport properties, high thermal conductivity, and large specific surface areas. This paper investigates the shape effects of nanoparticles on the Marangoni boundary layer of graphene−water nanofluid flow and heat transfer over a porous medium under the influences of the suction parameter. The graphene−water nanofluid flow was contained with various shapes of nanoparticles, namely sphere, column, platelet, and lamina. The problem is modeled in form of partial differential equations (PDES) with boundary conditions. The governing transport equations are converted into dimensionless form with the help of some suitable nondimensional variables. The solution of the problem was found numerically using the NDSolve technique of Mathematica 10.3 software. In addition, the numerical solutions were also compared with analytical results. The homotopy... [more]

This is an Aspen Plus v12 model for a Rectisol process used for removing CO2 from a shifted syngas stream arising from steam methane reforming for the purposes of Blue hydrogen production. It is intended for educational use, and is useful as a starting point for those interested in simulating this process. It is not optimized in any way, but it contains a working flowsheet for those interested in modifying it for your own purposes.

The simulation was developed using the simulation strategy given in Adams TA II, Khojestah Salkuyeh Y, Nease J. Processes and Simulations for Solvent-based CO2Capture and Syngas Cleanup. Chapter in: Reactor and process design for in sustainable energy technology. Elsevier (2014). Pages 163-232. ISBN: 978-0-444-59566-9. It is based on the process discussed in Doctor RD, Molburg JC, Thimmapuram PR, Berry GF, Livengood CD. Gasification combined cycle: carbon dioxide recovery, transport, and disposal. US DOE Report, Argonne National Laboratory ANL/ESD-24. 19... [more]