According to the structure of the air channel in the drying chamber of an automobile factory, a model of the original structure of the drying chamber was established. The air flow of this structure ...is analyzed based on the CFD simulation, and the velocity at specific points of the car shell being dried is also analyzed. The results show that the original drying chamber structure is optimized, the air flow is uniform in the drying air chamber and short circuit of air between inlet and outlet in the drying chamber is decreased.
As an essential part of hydrogen removal system in nuclear power plants, PARs could effectively eliminate released hydrogen and prevent potential hydrogen combustion during severe accidents. Serving ...as a basic composition in the catalytic section of PARs, catalytic element has a direct influence on the hydrogen removal capability of the PAR device. The CFD software STAR-CCM+ was utilized to develop models of catalytic channels containing three common catalytic elements (including catalytic plates, catalytic cylinders, and catalytic spheres). The elementary reaction mechanism was employed as the reaction kinetics model to define the chemical reaction process. This paper aims to evaluate the hydrogen removal capability of the catalytic elements in same operating conditions and analyze important factors for designing the structure of catalytic elements. All the catalytic surface area of catalytic elements was set to 0.045 m2 and inlet boundary conditions were settled identically. Our findings show that catalytic sphere exhibits the best hydrogen removal capability, which is attributed to the large lower half catalytic surface area of spheres. Catalytic plate with a lower height also demonstrates excellent hydrogen removal capability because of the presence of a larger catalytic area in the leading section. However, the hydrogen removal capability of catalytic cylinder is affected by the boundary layer separation vortex. A noticeable decrease in reaction rate occurs on the lower part of the sidewall surface, especially in the catalytic cylinder with a larger radius. In the structure design of catalytic elements, enlarging the catalytic surface area in the leading section and avoiding boundary layer separation on the catalytic surface are essential to further improve the hydrogen removal capability.
•Investigation on hydrogen removal capability of common catalytic elements.•Catalytic sphere exhibits the best hydrogen removal capability.•Enlarging catalytic surface area in the leading section eliminate more hydrogen.•Boundary layer separation retards the hydrogen removal rate.
The effect of H2O2 addition to the air on ammonia combustion was investigated in the current research using a computational fluid dynamics approach. The numerical simulation was conducted in a 10-kW ...laboratory-scale furnace. The oxidizer and fuel were injected into the furnace in a non-premixed mode. Furthermore, a kinetic study was carried out to analyze the sensitivity of NO production during combustion and to determine reaction pathways under various conditions. The findings indicate that the addition of H2O2 to the mixture increases flame temperature and NO levels, while decreasing N2O levels. Moreover, the study demonstrates that, with a maximum concentration of only 10 ppm, the amount of NO2 is very low under various percentages of H2O2 and different operating conditions. Furthermore, it is concluded that during ammonia/air combustion, lowering the oxidizer inlet temperature and increasing wall heat extraction may cause the combustion to become unstable. Under pure air oxidizer conditions, where Tin = 973 K and Twall = 1273 K, the combustion is stable. However, instability occurs when Twall falls to 1173 K. In this instance, adding merely 5 % H2O2 to the oxidizer is sufficient to provide self-sustaining and stable burning. More H2O2 must be introduced into the furnace to maintain stable combustion as Tin and Twall continue to decline. Interestingly, while adding H2O2 raises NO levels, decreasing the inlet and wall temperatures at higher H2O2 concentrations can help regulate NO emissions. These findings clearly indicate that introducing H2O2 into the fuel mixture could be a promising strategy for reducing the inlet temperature and enhancing heat extraction, which will both reduce energy consumption and increase system efficiency.
•A comprehensive CFD-kinetic model was developed to study NH3/H2O2/air combustion.•The addition of H2O2 to the oxidizer enhances flame temperature.•Adding H2O2 to the oxidizer raises NO levels, while reducing N2O.•The addition of H2O2 makes higher wall heat extraction achievable in NH3 combustion.
The aim of this study is to combine numerical and experimental approaches to evaluate the influence of pleat geometrical parameters on the pressure drop and air velocity field at the vicinity of ...pleated fibrous filters. For a given filter, three different geometrical pleat configurations (with various pleat heights and widths) are investigated at similar filtration velocities. Numerical simulations are validated based on experimental measurements in terms of pressure drop versus filtration velocity, and enable the influence of the filter geometry on the air flow pattern in its vicinity to be investigated. The influence of filter geometry on the pressure drop is evaluated from experiments carried out in a lab-scale air handling unit. For this purpose, pleated filter prototypes were designed in the laboratory.
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•CFD simulation, coupling interphase mass transfer, population balance model and kinetics for CO2 capture.•Prediction of CO2 absorption efficiency with 20% deviation from experimental ...data.•Illuminating internal transport and CO2 absorption process.•Reactor design guidelines for energy-efficiency CO2 capture.
This study employs non-thermal Computational Fluid Dynamics (CFD) simulations to explore the efficacy of a gas–liquid vortex reactor (GLVR) for intensifying CO2 capture. The investigation concentrates on the multiphase flow and mass transfer behavior in diverse GLVR experimental units. Employing a multiphase Euler-Euler CFD model integrated with a Population Balance Model (CFD-PBM), a mass transfer model, and reaction kinetics, allows us to accurately simulate the reactive absorption of CO2 into aqueous Monoethanolamine (MEA). Experiments are conducted using a 30 wt% MEA solution for CO2 absorption, serving the purpose of model validation. This comprehensive approach enables a simulation of complex dynamics within the GLVR, emphasizing bubble breakage, coalescence, and reactive mass transfer processes. Examining bubble size distribution, pressure drop, CO2 absorption efficiency, and energy input systematically across various reactor geometries and operational conditions, our findings demonstrate that an optimized GLVR configuration significantly enhances CO2 absorption compared to the original design. Furthermore, the optimized GLVR outperforms state-of-the-art process intensification equipment in terms of CO2 absorption rate per unit reactor volume and energy efficiency.
•Proppant transport is studied in fractures with intersections.•The equilibrium sand bed height decreases as the shear rate increases.•Proppant placement in the bypass slot increases as the shear ...rate increases.
Slickwater fracturing is a popular stimulation treatment in the unconventional oil and gas industry. It creates thin and long fractures that connect to pre-existing natural fractures and generate complex fracture networks. A large fraction of the fractured area is not usually propped due to the high density of typical proppants (sand) and low viscosity of the fracturing fluid. The goal of this work is to understand and optimize proppant transport in complex fracture networks. In this paper, proppant transport in fracture intersections is studied experimentally (using laboratory size slots) and numerically (using a multiphase dense discrete phase model). The orientation of natural fractures, proppant size and shear rate have been varied and the injected proppant volume is kept constant. Both experiments and simulations show three zones: bottom immobile sand bed zone, middle flowing slurry zone, and top clear fluid zone. The sand injected early forms the bottom of the sand bed; the sand injected later moves downstream and forms the top part of the bed. The entrance eroded region increases as the shear rate (or equivalently the water injection rate) increases. The sand bed length increases as the shear rate increases. The equilibrium sand bed height decreases as the shear rate increases and the sand size decreases. Proppant placement in the bypass slot increases as the shear rate increases and the bypass angle decreases. The numerical model using a dense discrete phase model (DDPM) captures the key features of the sand bed formation and transport.
Using solar stills in arid regions is one of the affordable solutions to provide the drinking water from brackish water sources. Improvement of the configuration of conventional solar stills to ...enhance the productivity has always been the concern of engineers and researchers in the field of solar energy and related branches. Time-consuming and costly processes of solar still fabrication motivate the scholars to perform mathematical and computational fluid dynamics (CFD) simulations of solar stills to estimate the productivity. This paper presents the latest numerical studies on various types of solar stills including single slope, double slope, multi-effect, tubular and so on. The review unveils that many other studies can be conducted in the future on CFD simulation of solar stills where various techniques such as utilizing nanotechnology, reflectors, storage materials, fans, and fins have been considered for the efficiency enhancement of solar desalination systems.
•A fast prediction method of temperature for two-phase flow and solids is proposed.•The accuracy of the novel joint algorithm is verified by a full flight profile.•The algorithm has good robustness ...under variable boundary conditions.•The computational efficiency is about 160 times faster than traditional algorithms.
In order to accelerate the temperature field calculation of fuel and tank wall protective materials, we propose a node-solid joint simulation method based on heat flow correction, in which the gas–liquid is used as a node for joint CFD (Computational Fluid Dynamics) calculation of the solid temperature field. Based on this method, we constructed a transient thermal analysis model of the fuel tank and performed a gas–liquid–solid conjugate heat transfer tight coupling simulation to obtain the wall heat transfer coefficient and the corrected heat flux under the specified thermal boundary conditions. The results show that the maximum relative errors of the average temperature of the gas–liquid node and the temperature field of the tank wall are less than 0.2 % and 6 %, respectively, and the calculation efficiency is about 160 times that of the traditional tight coupling calculation. When the solid boundary temperature is reduced by 200 K and increased by 500 K, the maximum relative error between the average temperature of the gas–liquid node and the solid temperature is less than 7 %. The algorithm has good robustness and accelerates the iterative design of the fuel tank. The accuracy of the algorithm was verified by the fuel temperature test experiment of the full flight profile.
•ANSYS® Forte simulation of a diesel engine converted to natural gas (NG) spark-ignition.•The model (G-equation, RANS) used a unique set of tuning parameters at all conditions.•NG composition had a ...relatively small effect on engine efficiency and emissions.•The model captured the double-peak heat release rate at advanced spark timing.•The model is suitable for flame behavior analysis inside a bowl-in-piston chamber.
The conversion of heavy-duty CI engines to natural gas (NG) SI operation have the potential to increase the use of NG in the transportation sector in the United States. More, the increased turbulence of a bowl-in-piston combustion chamber can increase the flame speed under more efficient lean conditions. The main objective of this study was to investigate if a 3D G-equation-based RANS simulation (i.e., reasonable computational costs and running times) can predict the efficiency and emissions of such converted engine, for various NG compositions and operating conditions. The model was validated with experimental data from a single-cylinder CI research engine that replaced the fuel injector with a spark plug and fumigated NG inside the intake manifold using a low-pressure gas injector. Using a unique set of model tuning parameters, the model was able to qualitatively predict the effect of NG composition on engine performance and emissions over a range of operating conditions that changed spark timing, equivalence ratio, and engine speed. The model also captured the double-peak heat release rate seen at advanced spark timing in the experiments. The results showed that a lower methane number (MN) increased peak pressure and indicated mean effective pressure. Higher H/C ratio advanced combustion phasing. More, higher MN lowered nitrogen oxides but increased unburned hydrocarbons emissions. However, while a lower MN increased carbon monoxide (CO) production during the combustion process, there was no clear trend for engine-out CO emissions. Overall, the predicted gas composition effects on engine efficiency and emissions were relatively small, at least for the range of operating conditions investigated here. However, the results suggest that the 3D CFD model described here is suitable for combustion phenomena analysis such the flame behavior in a bowl-in-piston combustion chamber.
Flow field structure can largely determine the output performance of Polymer electrolyte membrane fuel cell. Excellent channel configuration accelerates electrochemical reactions in the catalytic ...layer, effectively avoiding flooding on the cathode side. In present study, a three-dimensional, multi-phase model of PEMFC with a 3D wave flow channel is established. CFD method is applied to optimize the geometry constructions of three-dimensional wave flow channels. The results reveal that 3D wave flow channel is overall better than straight channel in promoting reactant gases transport, removing liquid water accumulated in microporous layer and avoiding thermal stress concentration in the membrane. Moreover, results show the optimal flow channel minimum depth and wave length of the 3D wave flow channel are 0.45 mm and 2 mm, respectively. Due to the periodic geometric characteristics of the wave channel, the convective mass transfer is introduced, improving gas flow rate in through-plane direction. Furthermore, when the cell output voltage is 0.4 V, the current density in the novel channel is 23.8% higher than that of conventional channel.
•A novel 3D wave flow channel is introduced to enhance the PEMFC performance.•The geometrical structure of 3D wave channel is optimized.•Current density in novel channel is 23.8% higher than conventional channel at 0.4 V.
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