Numerical modeling and simulation of chemical reaction effect on mass transfer through a fixed bed of particles

We studied the effect of a first order irreversible chemical reaction on mass transfer for two-phase flow systems in which the continuous phase is a fluid and the dispersed phase consists in catalystspherical particles. The reactive solute is transported by the fluid flow and penetrates through the particle surface by diffusion. The chemical reaction takes place within the bulk of the particle. Wehandle the problem by coupling mass balance equations for internal-external transfer with two boundary conditions: continuity of concentration and mass flux at the particle surface. We start with the case of a single isolated sphere. We propose a model to predict mass transfer coefficient (`reactive' Sherwood number) accounting for the external convection-diffusion along with internal diffusion-reaction. We validate the model through comparison with fully resolved Direct Numerical Simulations (DNS) performed by means of a boundary-fitted mesh method. For the simulation of multi-particle systems, we implemented a Sharp Interface Method to handle strong concentration gradients. We validate the implementation of the method thoroughly thanks to comparison with existing analytical solutions in case of diffusion, diffusion-reaction and by comparison with previously established correlations for convection-diffusion mass transfer. In case of convectiondiffusion- reaction, we validate the method and we evaluate its accuracy through comparisons with single particle simulations based on the boundary-fitted method. Later, we study the problem of three aligned-interacting spheres with internal chemical reaction. We propose a `reactive' Sherwood number model based on a known non-reactive prediction of mass transfer for each sphere. We validate the model by comparison with direct numerical simulations for a wide range of dimensionless parameters. Then, we study the configuration of a fixed bed of catalyst particles. We model the cup-mixing concentration profile, accounting for chemical reaction within the bed, and the mean surface and volume concentration profiles of the particles. We introduce a model for `reactive' Sherwood number that accounts for the solid volume fraction, in addition to the aforementioned effects. We compare the model to numerical simulations to evaluate its limitation

Coupling the fictitious domain and sharp interface methods for the simulation of convective mass transfer around reactive particles: towards a reactive Sherwood number correlation for dilute systems

We suggest a reactive Sherwood number model for convective mass transfer around reactive particles in a dilute regime. The model is constructed with a simple external-internal coupling and is validated with Particle-Resolved Simulation (PRS). The PRS of reactive particle-fluid systems requires numerical methods able to handle efficiently sharp gradients of concentration and potential discontinuities of gradient concentrations at the fluid-particle interface. To simulate mass transfer from reactive catalyst beads immersed in a fluid flow, we coupled the Sharp Interface Method (SIM) to a Distributed Lagrange Multiplier/Fictious Domain (DLM/FD) two-phase flow solver. We evaluate the accuracy of our numerical method by comparison to analytic solutions and to generic test cases fully resolved by boundary fitted simulations. A previous theoretical model that couples the internal diffusion-reaction problem with the external advection-diffusion mass transfer in the fluid phase is extended to the configuration of three aligned spherical particles representative of a dilute particle-laden flow. Predictions of surface concentration, mass transfer coefficient and chemical effectiveness factor of catalyst particles are validated by DLM-FD/SIM simulations. We show that the model captures properly the effect of an internal first order chemical reaction on the overall respective reactive Sherwood number of each sphere depending on their relative positions. The proposed correlation for the reactive Sherwood number is based on an existing non-reactive Sherwood number correlation. The model can be later used in Euler/Lagrange or Euler/ Euler modelling of dilute reactive particle-laden flows

Mass transfer towards a reactive particle in a fluid flow: Numerical simulations and modeling

We study mass transfer towards a solid spherical catalyst particle experiencing a first order irreversible reaction coupled to an external laminar flow. Internal chemical reaction and convective-diffusive mass transfer in the surrounding fluid flow are coupled by concentration and flux boundary conditions at the particle surface. Through this coupling, the mean particle surface and volume concentrations are predicted and the internal/external Sherwood numbers are obtained. We investigate the interplay between convection, diffusion, and reaction by computational fluid dynamics and establish a model for the mass transfer coefficient accounting for diffusion and internal first-order chemical reaction. We obtain a prediction of the mass transfer coefficient through mass balance or using the classical additivity rule. The model is numerically validated by fully resolved numerical simulations over a wide range of Reynolds number, Schmidt number and Thiele modulus which shows that assuming decoupled treatment of external and internal mass transfer gives very accurate predictions. Finally, we test the unsteady response of the model. The model predicts the evolution of the mean volume concentration for a particle placed in a steady convective-diffusive stream. Predictions of the unsteady model are in very good agreement with computed results

Performance optimization of simultaneous machine and automated guided vehicle scheduling using fuzzy logic controller based genetic algorithm.

The current trend in manufacturing technology is considered by two main items automation andflexibility. Flexible manufacturing system (FMS) is one of the most identified systems that include bothautomation and flexibility criteria. It comprises three principle elements: computer controlled machinetools, an automated material handling system and a computer control system. One of the automatedmaterials handling equipment in FMS is automated guided vehicles (AGVs). Integrated scheduling ofAGVs and machines is an essential factor contributing to the efficiency of the manufacturing system inFMS environment. Previously, genetic algorithm (GA) is considered as a heuristic method to solve AGVscheduling problem. GA may not be able to achieve the global optimum due to premature convergencebecause of control’s lack on its operators parameters. Fuzzy logic controller (FLC) is proposed tocontrol the behavior of GA during solving the scheduling problem of AGVs. This paper presents a job-based GA that is based on job sequencing. Through the optimization, the FLC is used to control the GAoperators (crossover and mutation rate) simultaneous to solve the AGV scheduling proble

In-vitro cytotoxic and radiosensitizing evaluation of novel 2-pyridone, isoquinoline, chromene and chromenopyridone derivatives

On the account of the reported anticancer activity of 2-pyridone, a new series of ethyl-1,6-dihydropyridine-3-carboxylate (4a-j), 1-oxo-1,2-dihydroisoquinoline-7-carbonitrile (6a-h), 2H-chromene (7,8) and 3H-chromeno[3,4-c]pyridone derivatives (9,10) were synthesized and tested for in-vitro anticancer activity against Ehrlich Ascites Carcinoma (EAC) cell line and human liver cell line (HEPG2). The structures of the synthesized compounds were confirmed by analytical and spectral data. Furthermore, radiosensitization study was performed for the most potent compounds (4a, 4d, 6a, 6c, 6e and 10)

Sharing clinical information in P2P environment with RBAC mechanism.

This paper proposes a Peer-to-Peer (P2P) distributed database system (PDBS) with Role Based Access Control (RBAC) mechanism for sharing the clinical information. In the proposed system, peers as health centers have their own local databases and information in these local databases can be shared among health centers through user queries. As a fully decentralized P2P distributed database information sharing system, each health center has both server and client functions. Each health center can act as a client that sends queries to others and also can act as a server which responses to the client health center. The proposed system supports health center operators to send queries and update queries to other health centers and integrates the distributed query results and displays the results through a user interface based on the role of the user in the system. Furthermore, health centers are able to discover other online health centers to send queries and receive responses. The proposed system is implemented with the JXTA platform in P2P environment

Numerical simulations and modelling of mass transfer through random assemblies of catalyst particles: from dilute to dense reactive particulate regime

We study mass transfer through random assemblies of fixed spherical catalyst particles experiencing an external convective-diffusive fluid stream. Chemical species are transported through the array and are diffused from fluid to solid phase through particles surface. An internal first order irreversible chemical reaction takes place within the porous catalyst particles. We address the determination of mass transfer coefficient by performing direct numerical simulations with fully internal-external coupling using concentration and flux continuity boundary conditions at the solid-fluid interface. We derive a theoretical prediction of the profiles of cup-mixing concentration, average of mean surface and average of mean volume concentration of the particles along the height of the domain. The model for the dimensionless mass transfer coefficient (‘reactive’ Sherwood number) is accounting for the five dimensionless parameters that control the physics of the system: the Reynolds number , the Schmidt number, the Damköhler  number, the internal-to-external diffusion coefficient ratio and the solid volume fraction . We use a coupled Sharp Interface/ Discrete Lagrange Multiplier-Fictitious Domain Method (SIM-DLM/FD), thoroughly validated in our previous study (Sulaiman et al., 2019) to test the accuracy of the model over a wide range of dimensionless parameters and solid volume faction (from dilute to dense regime). We show and discuss the limitations of the proposed model

Isolation of Thermoalkalophilic-?-amylase Producing Bacteria and Optimization of Potato Waste Water Medium for Enhancement of ?-amylase Production

Sixty one thermoalkalophilic bacteria were isolated from soil samples in Saudi Arabia’s southern region. Isolate TA-38, obtained from the Tanomah region, showed the best performance for enzyme production and was submitted for further study. It was identified as Bacillus axarquiensis based on 16S rRNA gene sequencing studies. The feasibility of using potato waste water as a simple and cheap medium for the production of ?-amylase was evaluated compared with starch broth medium. The production of ?-amylase in the potato waste water medium was only 13.8% less than that of the starch medium. Maximum enzyme production was achieved after 48 hours of cultivation at the beginning of the stationary phase at pH 10.0 and 50 0C. The appropriate addition of starch; nitrogen; phosphate; and calcium to potato waste water significantly enhanced the production of ?-amylase. The enzyme production reached a maximum of 64.5 Uml-1 with the potato wastewater adding with 0.5 % starch; 0.4 % yeast extract; 0.04% CaCl2-2H2O and 0.05 % KH2PO4.  The optimization of the potato waste water medium led to an approximately 4.02 fold increase in the production of ?-amylase compared to starch broth medium. Data indicated that the potato waste water contained substrates which could be used by bacterial isolate for the production of ?-amylase production and the developed procedure was cost effective since it requires only a slightly addition of nutrients to the medium. Keywords: Isolation; ?-amylase; 16S rRNA; Production; Potato waste water; Thermoalkaliphilic bacteria

Hydrogen production via catalyst of green laser, molybdenum and ethanol

Electrolysis is an electrochemical process which is known as a green technology. Laser irradiation and the presence of catalyst in water electrolysis are identified as ways of improving the efficiency and increment of hydrogen production. The enhancement of hydrogen production through water electrolysis is obtained by adding molybdenum to increase the current in electrochemical cell and ethanol as an agent in photochemical reaction. In addition, diode pumped solid-state laser green laser at 532 nm is employed with the purpose to compensate the residual electrical field effect. The combination of the three catalysts is found more powerful to cause water splitting, thus produced 5 times greater H2 production in comparison to the action of individual catalyst

Numerical modelling of long flexible fibers in homogeneous isotropic turbulence

We numerically investigated the transport, deformation and buckling events of an isolated elastic fiber in Taylor-Green vortices and studied the dynamics of long filaments in homogeneous isotropic turbulence. The fiber is modelled by an assembly of spherical beads. The contact between beads enforces the inextensibility of the filament while bending is accounted for by the Gears Bead Model (GBM) proposed by Delmotte et al. (2015). In the cellular Taylor-Green flow, the buckling probability is a function of a dimensionless number, called Sperm number, which is a balance between the compression rate of the flow and the elastic response of the filament. The shapes of the filament and its ability to buckle have been successfully validated through comparisons with experiments from the work by Quennouz et al. (2015). The deformation statistics of long flexible fibers in sustained homogeneous isotropic turbulence were analyzed for various flow and fiber material conditions. Two regimes have been identified depending on the ratio of fiber length to persistence length which is a measure of turbulent forcing to flexibility. The numerical results are in good agreement with existing experimental data (C. Brouzet et al., Phys. Rev. Lett. 112, 074501 (2014)) validating the assumptions of our model for the configurations we investigated