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Records with Keyword: Computational Fluid Dynamics
Showing records 1 to 25 of 85. [First] Page: 1 2 3 4 Last
Numerical Reconstruction of Hazardous Zones after the Release of Flammable Gases during Industrial Processes
Zdzislaw Salamonowicz, Andrzej Krauze, Malgorzata Majder-Lopatka, Anna Dmochowska, Aleksandra Piechota-Polanczyk, Andrzej Polanczyk
December 6, 2022 (v1)
The storage of large numbers of batteries and accumulators is associated with an increased risk of their ignition, which results in the release of significant amounts of hydrogen into the environment. The aim of the study was to reconstruct hazardous zones after hydrogen and liquefied propane−butane (reference gas) release for different industrial processes with the use of numerical methods. Two numerical tools (Fire Dynamics Simulator and Ansys software) were applied for the three-dimensional reconstruction of flammable gas release. Propane−butane was produced from aerosol packages, and hydrogen was produced during battery charging. Emission was analyzed in an industrial building, and both emissions were independent processes. The obtained results indicated that the hazardous zones correspond to the lower explosive level concentrations for both analyzed gasses. Moreover, the high-resolution computational fluid dynamic (CFD) model for flammable gas emissions provided noninvasive and di... [more]
Numerical Simulation of the Aerosol Particle Motion in Granular Filters with Solid and Porous Granules
Olga V. Soloveva, Sergei A. Solovev, Ruzil R. Yafizov
October 31, 2022 (v1)
Keywords: Computational Fluid Dynamics, DEM, filter quality factor, granular filter, microporosity, particle deposition efficiency, pressure drop, spherical granules
In this work, a study was carried out to compare the filtering and hydrodynamic properties of granular filters with solid spherical granules and spherical granules with modifications in the form of micropores. We used the discrete element method (DEM) to construct the geometry of the filters. Models of granular filters with spherical granules with diameters of 3, 4, and 5 mm, and with porosity values of 0.439, 0.466, and 0.477, respectively, were created. The results of the numerical simulation are in good agreement with the experimental data of other authors. We created models of granular filters containing micropores with different porosity values (0.158−0.366) in order to study the micropores’ effect on the aerosol motion. The study showed that micropores contribute to a decrease in hydrodynamic resistance and an increase in particle deposition efficiency. There is also a maximum limiting value of the granule microporosity for a given aerosol particle diameter when a further increas... [more]
Development of a Hydropower Turbine Using Seawater from a Fish Farm
Md Rakibuzzaman, Sang-Ho Suh, Hyoung-Ho Kim, Youngtae Ryu, Kyung Yup Kim
October 31, 2022 (v1)
Keywords: Computational Fluid Dynamics, design factors, fish farm, optimum model, performance test, small hydropower, tubular turbine
Discharge water from fish farms is a clean, renewable, and abundant energy source that has been used to obtain renewable energy via small hydropower plants. Small hydropower plants may be installed at offshore fish farms where suitable water is obtained throughout the year. It is necessary to meet the challenges of developing small hydropower systems, including sustainability and turbine efficiency. The main objective of this study was to investigate the possibility of constructing a small hydropower plant and develop 100 kW class propeller-type turbines in a fish farm with a permanent magnet synchronous generator (PMSG). The turbine was optimized using a computer simulation, and an experiment was conducted to obtain performance data. Simulation results were then validated with experimental results. Results revealed that streamlining the designed shape of the guide vane reduced the flow separation and improved the efficiency of the turbine. Optimizing the shape of the runner vane decre... [more]
Simulation of Flexible Fibre Particle Interaction with a Single Cylinder
Naser Hamedi, Lars-Göran Westerberg
October 12, 2022 (v1)
Keywords: Computational Fluid Dynamics, fiber flexibility, fiber model, fiber suspension, particulate flow
In the present study, the flow of a fibre suspension in a channel containing a cylinder was numerically studied for a very low Reynolds number. Further, the model was validated against previous studies by observing the flexible fibres in the shear flow. The model was employed to simulate the rigid, semi-flexible, and fully flexible fibre particle in the flow past a single cylinder. Two different fibre lengths with various flexibilities were applied in the simulations, while the initial orientation angle to the flow direction was changed between 45° ≤ θ ≤ 75°. It was shown that the influence of the fibre orientation was more significant for the larger orientation angle. The results highlighted the influence of several factors affecting the fibre particle in the flow past the cylinder.
Computational Fluid Dynamics Modeling of Rotating Annular VUV/UV Photoreactor for Water Treatment
Minghan Luo, Wenjie Xu, Xiaorong Kang, Keqiang Ding, Taeseop Jeong
October 14, 2021 (v1)
Keywords: Computational Fluid Dynamics, MB, photoreactor, VUV, water treatment
The ultraviolet photochemical degradation process is widely recognized as a low-cost, environmentally friendly, and sustainable technology for water treatment. This study integrated computational fluid dynamics (CFD) and a photoreactive kinetic model to investigate the effects of flow characteristics on the contaminant degradation performance of a rotating annular photoreactor with a vacuum-UV (VUV)/UV process performed in continuous flow mode. The results demonstrated that the introduced fluid remained in intensive rotational movement inside the reactor for a wide range of inflow rates, and the rotational movement was enhanced with increasing influent speed within the studied velocity range. The CFD modeling results were consistent with the experimental abatement of methylene blue (MB), although the model slightly overestimated MB degradation because it did not fully account for the consumption of OH radicals from byproducts generated in the MB decomposition processes. The OH radical... [more]
Comparative Study on CFD Turbulence Models for the Flow Field in Air Cooled Radiator
Chao Yu, Xiangyao Xue, Kui Shi, Mingzhen Shao, Yang Liu
July 29, 2021 (v1)
Keywords: Computational Fluid Dynamics, engine compartment, heat transfer, turbulent model, vortex
This paper compares the performances of three Computational Fluid Dynamics (CFD) turbulence models, Reynolds Average Navier-Stokes (RANS), Detached Eddy Simulation (DES), and Large Eddy Simulation (LES), for simulating the flow field of a wheel loader engine compartment. The distributions of pressure fields, velocity fields, and vortex structures in a hybrid-grided engine compartment model are analyzed. The result reveals that the LES and DES can capture the detachment and breakage of the trailing edge more abundantly and meticulously than RANS. Additionally, by comparing the relevant calculation time, the feasibility of the DES model is proved to simulate the three-dimensional unsteady flow of engine compartment efficiently and accurately. This paper aims to provide a guiding idea for simulating the transient flow field in the engine compartment, which could serve as a theoretical basis for optimizing and improving the layout of the components of the engine compartment.
Thermal Hazard Analysis of Styrene Polymerization in Microreactor of Varying Diameter
Junjie Wang, Lei Ni, Jiawei Cui, Juncheng Jiang, Kuibin Zhou
July 29, 2021 (v1)
Keywords: Computational Fluid Dynamics, microreactor, styrene polymerization, thermal runaway
Polymerization is a typical exothermic reaction in the fine chemical industry, which is easy to cause thermal runaway. In order to lower the thermal runaway risk of polymerization, a microreactor was adopted in this study to carry out styrene thermal polymerization. The hydrodynamic model and the fluid−solid coupling model of thermal polymerization of styrene were combined by using the computation fluid dynamics (CFD) method to build a three-dimensional steady-state model of the batch and the microreactor and compare. The results indicated that the maximum temperature of the polymerization in the microreactor was only 150.23 °C, while in the batch reactor, it was up to 371.1 °C. Therefore, the reaction temperature in the microreactor could be controlled more effectively compared with that in the batch reactor. During the reaction process, jacket cooling may fail, which would lead to an adiabatic situation. According to the divergence criterion (DIV), the thermal runaway of the polymeri... [more]
Predicting By-Product Gradients of Baker’s Yeast Production at Industrial Scale: A Practical Simulation Approach
Christopher Sarkizi Shams Hajian, Cees Haringa, Henk Noorman, Ralf Takors
June 21, 2021 (v1)
Keywords: bioprocess engineering, bioreactor, Computational Fluid Dynamics, concentration gradients, digital twin, mechanistic kinetic model, Saccharomyces cerevisiae, scale-down, scale-up
Scaling up bioprocesses is one of the most crucial steps in the commercialization of bioproducts. While it is known that concentration and shear rate gradients occur at larger scales, it is often too risky, if feasible at all, to conduct validation experiments at such scales. Using computational fluid dynamics equipped with mechanistic biochemical engineering knowledge of the process, it is possible to simulate such gradients. In this work, concentration profiles for the by-products of baker’s yeast production are investigated. By applying a mechanistic black-box model, concentration heterogeneities for oxygen, glucose, ethanol, and carbon dioxide are evaluated. The results suggest that, although at low concentrations, ethanol is consumed in more than 90% of the tank volume, which prevents cell starvation, even when glucose is virtually depleted. Moreover, long exposure to high dissolved carbon dioxide levels is predicted. Two biomass concentrations, i.e., 10 and 25 g/L, are considered... [more]
Numerical Investigation of the Characteristics of the In-Cylinder Air Flow in a Compression-Ignition Engine for the Application of Emulsified Biofuels
Mohd Fadzli Hamid, Mohamad Yusof Idroas, Mazlan Mohamed, Shukriwani Sa'ad, Teoh Yew Heng, Sharzali Che Mat, Muhamad Azman Miskam, Muhammad Khalil Abdullah
June 10, 2021 (v1)
Keywords: biofuel, compression-ignition (CI) engine, Computational Fluid Dynamics, emulsified biofuel, guide vanes, piston
This paper presents a numerical analysis of the application of emulsified biofuel (EB) to diesel engines. The study performs a numerical study of three different guide vane designs (GVD) that are incorporated with a shallow depth re-entrance combustion chamber (SCC) piston. The GVD variables were used in three GVD models with different vane heights, that is, 0.2, 0.4 and 0.6 times the radius of the intake runner (R) and these were named 0.20R, 0.40R and 0.60R. The SCC piston and GVD model were designed using SolidWorks 2017, while ANSYS Fluent version 15 was used to perform cold flow engine 3D analysis. The results of the numerical study showed that 0.60R is the optimum guide vane height, as the turbulence kinetic energy (TKE), swirl ratio (Rs), tumble ratio (RT) and cross tumble ratio (RCT) in the fuel injection region improved from the crank angle before the start of injection (SOI) and start of combustion (SOC). This is essential to break up the heavier-fuel molecules of EB so that... [more]
Digital Twinning Process for Stirred Tank Reactors/Separation Unit Operations through Tandem Experimental/Computational Fluid Dynamics (CFD) Simulations
Blaž Oblak, Simon Babnik, Vivian Erklavec-Zajec, Blaž Likozar, Andrej Pohar
June 10, 2021 (v1)
Keywords: Computational Fluid Dynamics, dissolution modelling, mixing simulation, reactor design
Computational fluid dynamics simulations (CFD) were used to evaluate mixing in baffled and unbaffled vessels. The Reynolds-averaged Navier−Stokes k−ε model was implemented in OpenFOAM for obtaining the fluid flow field. The 95% homogenization times were determined by tracer tests. Experimental tests were conducted by injecting sodium chloride into the vessel and measuring the conductivity with two conductivity probes, while the simulations replicated the experimental conditions with the calculation of the transport of species. It was found that the geometry of the system had a great effect on the mixing time, since the irregular flow distribution, which can be obtained with baffles, can lead to local stagnation zones, which will increase the time needed to achieve the homogenization of the solute. It was also found that measuring local, pointwise concentrations can lead to a high underestimation of the global mixing time required for the homogenization of the entire vessel. Dissolution... [more]
The Effect of Root Clearance on Mechanical Energy Dissipation for Axial Flow Pump Device Based on Entropy Production
Yanjun Li, Yunhao Zheng, Fan Meng, Majeed Koranteng Osman
June 10, 2021 (v1)
Keywords: axial-flow pump, Computational Fluid Dynamics, energy dissipation, entropy production, root clearance radius
The axial flow pump is a low head, high discharge pump usually applicable in drainage and irrigation facilities. A certain gap should be reserved between the impeller blade root and the impeller hub to ensure the blade adjustability to broaden the high-efficiency area. The pressure difference between its blade surface induces leakage flow in the root clearance region, which decreases hydraulic performance and operational stability. Therefore, this study was carried out to investigate the effect of root clearance on mechanical energy dissipation using numerical simulation and entropy production methods. The numerical model was validated with an external characteristics test, and unsteady flow simulations were conducted on the axial flow pump under four different root clearance radii. The maximum reductions of 15.5% and 6.8% for head and hydraulic efficiency are obtained for the largest root clearance of 8 mm, respectively. The dissipation based on entropy theory consists of indirect dis... [more]
A Numerical Study on the Pilot Injection Conditions of a Marine 2-Stroke Lean-Burn Dual Fuel Engine
Hao Guo, Song Zhou, Jiaxuan Zou, Majed Shreka
May 25, 2021 (v1)
Keywords: Computational Fluid Dynamics, dual-fuel engine, pre-combustion chamber, Simulation, two-stroke
The global demand for clean fuels is increasing in order to meet the requirements of the International Maritime Organization (IMO) of 0.5% global Sulphur cap and Tier III emission limits. Natural gas has begun to be popularized on liquefied natural gas (LNG) ships because of its low cost and environment friendly. In large-bore marine engines, ignition with pilot fuel in the prechamber is a good way to reduce combustion variability and extend the lean-burn limit. However, the occurrence of knock limits the increase in power. Therefore, this paper investigates the effect of pilot fuel injection conditions on performance and knocking of a marine 2-stroke low-pressure dual-fuel (LP-DF) engine. The engine simulations were performed under different pilot fuel parameters. The results showed that the average in-cylinder temperature, the average in-cylinder pressure, and the NOx emissions gradually decreased with the delay of the pilot injection timing. Furthermore, the combustion situation gra... [more]
A CFD-Based Shape Design Optimization Process of Fixed Flow Passages in a Francis Hydro Turbine
Ujjwal Shrestha, Young-Do Choi
May 24, 2021 (v1)
Keywords: Computational Fluid Dynamics, fixed flow passage, flow uniformity, Francis turbine, shape optimization
In recent times, optimization began to be popular in the turbomachinery field. The development of computational fluid dynamics (CFD) analysis and optimization technology provides the opportunity to maximize the performance of hydro turbines. The optimization techniques are focused mainly on the rotating components (runner and guide vane) of the hydro turbines. Meanwhile, fixed flow passages (stay vane, casing, and draft tube) are essential parts for the proper flow uniformity in the hydro turbines. The suppression of flow instabilities in the fixed flow passages is an inevitable process to ensure the power plant safety by the reduction of vortex-induced vibration and pressure pulsation in the hydro turbines. In this study, a CFD-based shape design optimization process is proposed with response surface methodology (RSM) to improve the flow uniformity in the fixed flow passages of a Francis hydro turbine model. The internal flow behaviors were compared between the initial and optimal sha... [more]
Aerodynamic Performance of an Octorotor SUAV with Different Rotor Spacing in Hover
Yao Lei, Yuhui Huang, Hengda Wang
May 17, 2021 (v1)
Keywords: aerodynamic performance, Computational Fluid Dynamics, hover, octorotor SUAV, rotor spacing, vortices distribution
To study the aerodynamic performance of hovering octorotor small unmanned aerial vehicles (SUAV) with different rotor spacing, the computational fluid dynamics (CFD) method is applied to analyze the flow field of an octorotor SUAV in detail. In addition, an experimental platform is built to measure the thrust and power of the rotors with rotor spacing ratios L/D of 1.0, 1.2, 1.4, 1.6, and 1.8, sequentially. According to the theory of momentum, rotor aerodynamic performance is obtained with qualitative analysis. Further analysis with numerical simulation is presented with the flow field of the octorotor SUAV, the vorticity distribution, velocity distribution, pressure distribution, and streamline. The results show that the aerodynamic performance varies with the rotor spacing. Specifically, the aerodynamic performance is poor at L/D = 1.0, which is accompanied with strong interaction of wake and tip vortexes and interaction with each other. However, the aerodynamic efficiency is much im... [more]
CFD Modeling of Spatial Inhomogeneities in a Vegetable Oil Carbonation Reactor
Attila Egedy, Alex Kummer, Sébastien Leveneur, Tamás Varga, Tibor Chován
May 17, 2021 (v1)
Keywords: biomass valorization, carbonation modeling, Computational Fluid Dynamics, spatial coordinate-based material properties
Fossil materials are widely used raw materials in polymerization processes; hence, in many cases, the primary goal of green and sustainable technologies is to replace them with renewables. An exciting and promising technology from this aspect is the isocyanate-free polyurethane production using vegetable oil as a raw material. Functional compounds can be formed by the epoxidation of vegetable oils in three reaction steps: epoxidation, carbonation, and aminolysis. In the case of vegetable oil carbonation, the material properties vary strongly, with the composition affecting the solubility of CO2 in the reaction mixture. Many attempts have been made to model these interactions, but they generally do not account for the changes in the material properties in terms of spatial coordinates. A 2D CFD model based on the combination of the k-ε turbulence model and component mass balances considering the spatial inhomogeneities on the performance of the reactor was created. After the evaluation o... [more]
Numerical Simulation of Combustion in 35 t/h Industrial Pulverized Coal Furnace with Burners Arranged on Front Wall
Jiade Han, Lingbo Zhu, Yiping Lu, Yu Mu, Azeem Mustafa, Yajun Ge
April 29, 2021 (v1)
Keywords: combustion characteristics, Computational Fluid Dynamics, industrial pulverized coal furnace, swirling burner
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]
The Hydrodynamics and Mixing Performance in a Moving Baffle Oscillatory Baffled Reactor through Computational Fluid Dynamics (CFD)
Hamid Mortazavi, Leila Pakzad
April 27, 2021 (v1)
Keywords: Computational Fluid Dynamics, dynamic mesh, hydrodynamics, mixing indices, OBR
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]
Thermal Assessment of a Micro Fibrous Fischer Tropsch Fixed Bed Reactor Using Computational Fluid Dynamics
Aya E. Abusrafa, Mohamed S. Challiwala, Benjamin A. Wilhite, Nimir O. Elbashir
April 26, 2021 (v1)
Keywords: Computational Fluid Dynamics, entrapped cobalt catalyst, Fischer Tropsch, Syngas, thermal management
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]
A Numerical Investigation on De-NOx Technology and Abnormal Combustion Control for a Hydrogen Engine with EGR System
Hao Guo, Song Zhou, Jiaxuan Zou, Majed Shreka
April 16, 2021 (v1)
Keywords: Computational Fluid Dynamics, exhaust gas recirculation, hydrogen engine, knocking, pre-ignition
The combustion emissions of the hydrogen-fueled engines are very clean, but the problems of abnormal combustion and high NOx emissions limit their applications. Nowadays hydrogen engines use exhaust gas recirculation (EGR) technology to control the intensity of premixed combustion and reduce the NOx emissions. This study aims at improving the abnormal combustion and decreasing the NOx emissions of the hydrogen engine by applying a three-dimensional (3D) computational fluid dynamics (CFD) model of a single-cylinder hydrogen-fueled engine equipped with an EGR system. The results indicated that peak in-cylinder pressure continuously increased with the increase of the ignition advance angle and was closer to the top dead center (TDC). In addition, the mixture was burned violently near the theoretical air−fuel ratio, and the combustion duration was shortened. Moreover, the NOx emissions, the average pressure, and the in-cylinder temperature decreased as the EGR ratio increased. Furthermore,... [more]
Large Eddy Simulations of Reactive Mixing in Jet Reactors of Varied Geometry and Size
Krzysztof Wojtas, Wojciech Orciuch, Łukasz Makowski
March 1, 2021 (v1)
Keywords: Computational Fluid Dynamics, confined impinging jet reactors, large eddy simulation, Mixing, parallel chemical reactions
We applied large eddy simulation (LES) to predict the course of reactive mixing carried out in confined impinging jet reactors (CIJR). The reactive mixing process was studied in a wide range of flow rates both experimentally and numerically using computational fluid dynamics (CFD). We compared several different reactor geometries made in different sizes in terms of both reaction yields and mixing efficiency. Our LES model predictions were validated using experimental data for the tracer concentration distribution and fast parallel chemical test reactions, and compared with the k-ε model supplemented with the turbulent mixer model. We found that the mixing efficiency was not affected by the flow rate only at the highest tested Reynolds numbers. The experimental results and LES predictions were found to be in good agreement for all reactor geometries and operating conditions, while the k-ε model well predicted the trend of changes. The CFD method used, i.e., the modeling approach using c... [more]
Experimental and Numerical Study on Hydraulic Performance of Chevron Brazed Plate Heat Exchanger at Low Reynolds Number
Yi Zhong, Kai Deng, Shenglang Zhao, Jinlin Hu, Yingjie Zhong, Qingyong Li, Zenan Wu, Zhiming Lu, Qing Wen
February 22, 2021 (v1)
Keywords: analysis, brazed plate heat exchanger, Computational Fluid Dynamics, corrugated, Darcy friction factor, low Reynolds number, pressure drop
Few experiments have been performed to investigate the hydraulic performance in a chevron brazed plate heat exchanger (BPHE) with the narrow channel at lower Reynolds number. The hydraulic characteristics of seven types of chevron BPHEs were investigated experimentally and numerical simulation revealed the effects of structural parameters on hydraulic performances. The correlations between friction factor f and Re were fitted out based on more than 500 sets of pressure drop data. The research results show that there is a power-law between f and Re; which has a similar trend but a different amplitude for different plates, and the exponent of the power-law could be approximate to a constant. Numerical results show that the pressure drop Δp is positively correlated with the corrugated angle and spacing, however, negatively correlated with the corrugated height. Research on the hydraulic performance is significant for the optimal design of BPHE.
Comprehensive Improvement of Mixed-Flow Pump Impeller Based on Multi-Objective Optimization
Mengcheng Wang, Yanjun Li, Jianpin Yuan, Fan Meng, Desmond Appiah, Jiaqi Chen
December 17, 2020 (v1)
Keywords: 3D inverse design, circulation, Computational Fluid Dynamics, mixed-flow pump, multi-objective optimization
The spanwise distribution of impeller exit circulation (SDIEC) has a significant effect on the impeller performance, therefore, there is a need for its consideration in the optimization design of mixed-flow pumps. In this study, a combination optimization system, including a 3D inverse design method (IDM), computational fluid dynamics (CFD), Latin hypercube sampling (LHS) method, response surface model (RSM), and non-dominated sorting genetic algorithm (NSGA-Ⅱ) was used to improve the performance of the mixed-flow pump after considering the effect of SDIEC on the performance of the impeller. The CFD results confirm the accuracy and credibility of the optimization results because of the good agreement the CFD results established with the experimental measurements. Compared with the original impeller, the pump efficiency of the preferred impeller at 0.8Qdes, 1.0Qdes, and 1.2Qdes improved by 0.63%, 3.39%, and 3.77% respectively. The low-pressure region on the blade surface reduced by 96.9... [more]
CFD and Experimental Characterization of a Bioreactor: Analysis via Power Curve, Flow Patterns and k L a
Luis A. Ramírez, Edwar L. Pérez, Cesar García Díaz, Dumar Andrés Camacho Luengas, Nicolas Ratkovich, Luis H. Reyes
November 9, 2020 (v1)
Subject: Biosystems
Keywords: bioreactors, Computational Fluid Dynamics, impellers, mass transfer, oxygen diffusion, stirred tank
Mixing operations in biological processes is of utmost importance due to its effect on scaling-up and heat and mass transfer. This paper presents the characterization of a bench-top bioreactor with different impeller configurations, agitation and oxygen transfer rates, using CFD simulations and experimental procedures. Here, it is demonstrated that factors such as the type of impeller and the flow regime can drastically vary the operation as in the preparation of cultures. It was observed that the bioreactor equipped with a Rushton generates a k L a of 0.0056 s−1 for an agitation velocity and airflow rate of 250 RPM and 5 L/min, respectively. It is suitable result for the dissolved oxygen (DO) but requires a considerable amount of power consumption. It is here where the importance of the agitator’s diameter can be observed, since, in the case of the two propeller types studied, lower energy consumption can be achieved with a smaller diameter, as well as a much smaller shear c... [more]
A Numerical Investigation on the Optimization of Uneven Flow in a Marine De-SOx Scrubber
Hao Guo, Song Zhou, Majed Shreka, Yongming Feng
November 9, 2020 (v1)
Keywords: Computational Fluid Dynamics, droplets distribution, exhaust gas cleaning, nozzles distribution, sodium-alkali method
According to regulations from the International Maritime Organization (IMO), the sulfur content of vessels must not exceed 0.5% outside the Emission Control Areas (ECAs) starting from 2020. The marine exhaust gas desulfurization (De-SOx) system is the most feasible technology to meet the increasing regulations, but there is always a large swirl at the bottom of the scrubber causing uneven flow past the sprays. Solving this problem by adjusting the spray is a feasible method. The exhaust gas at 485 K and injection liquid at 305 K are simulated to optimize the flow field in a De-SOx scrubber. The results indicated that the flue gas was easily concentrated in the left side area of the scrubber and this part of hot gas could escape from the scrubber. By controlling the nozzles distribution and the nozzles angle, it was possible to reduce the droplets to hit the wall and improve the utilization rate of the washing liquid. The nozzles were arranged up and down in different positions, which r... [more]
Nanofluid Flow Past a Stretching Plate
Gabriella Bognár, Mohamad Klazly, Krisztián Hriczó
November 9, 2020 (v1)
Keywords: Computational Fluid Dynamics, moving surface, nanofluid, Nusselt number, Sakiadis flow, similarity method, skin friction
Viscous nanofluid flow due to a sheet moving with constant speed in an otherwise quiescent medium is studied for three types of nanofluids, such as alumina (Al2O3), titania (TiO2), and magnetite (Fe3O4), in a base fluid of water. The heat and mass transfer characteristics are investigated theoretically using the boundary layer theory and numerically with computational fluid dynamics (CFD) simulation. The velocity, temperature, skin friction coefficient, and local Nusselt number are determined. The obtained results are in good agreement with known results from the literature. It is found that the obtained results for skin friction and for the Nusselt number are slightly greater than those obtained via boundary layer theory.
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