Baffle Arrangements Research Articles

Microcontaminants Removal in Constructed Wetlands with Different Baffle Arrangements and Cultivated with Pennisetum setaceum

Microcontaminants Removal in Constructed Wetlands with Different Baffle Arrangements and Cultivated with Pennisetum setaceum

Experimental tests and prediction of insertion loss for cubical sound insulating enclosures with single homogeneous walls

Limiting the excessive noise of machines and devices can be performed with the use of screens in the form of baffles or acoustic enclosures. Knowledge of their acoustic properties is essential in the proper construction of baffles. The basic properties include the airborne sound insulation of the baffle, and the insertion loss in the case of the arrangement of several baffles constituting the acoustic enclosure. Both parameters can be determined through experimental tests, including laboratory ones and using theoretical computational models.The article presents the results of both experimental and model tests of the sound insulating effectiveness of enclosures. The proposed calculation model for the insertion loss of sound insulating enclosures, intended for mid- and high-frequency ranges, was determined on the basis of the sound transmission loss of a homogeneous baffle, which was calculated from its material data using a theoretical model developed within previous studies, based on the Davy and Sharp models. For the low-frequency range, the use of a modified Oldham model for close-fitting enclosures was proposed. The new calculation model was validated for six enclosure variants consisting of five identical square plates, made of materials such as steel, aluminium, plexiglass, polypropylene and gypsum. For this purpose, the developed prototype stand for testing acoustic enclosures was used, with the possibility of mounting walls of different thickness. A good correlation between the results of the insertion loss spectral characteristic calculations and the results from experimental tests was obtained using the proposed model, in the entire considered frequency range of 100–5000 Hz.

Reduction of bubble coalescence by louver baffles in fluidized bed gasifier

Bubble coalescence is a cause of decrease in gas–solid contact in a bubbling bed gasifier. This study used computational fluid dynamics (CFD) to explore a louver baffles arrangement that could reduce the bubble coalescence in the bubbling bed gasifier fueled by biomass. The results showed that 20 mm-gap baffles were not able to reduce the bubble coalescence while the 10 mm-gap baffles were effective to reduce the bubble size and slow down the bubble coalescence. The 10 mm-gap baffles also provided better gas–solid contact thorough the system. In addition, these baffles arrangement would steadily maintain full fluidization above the baffles.

SIMULASI KESTABILAN PROTOTYPE UAV-SPRAYER BERBASIS QUADCOPTER TERHADAP PENAMBAHAN SEKAT PADA PENAMPUNG CAIRAN

The use of UAVs has begun to penetrate the world of agriculture. One of the functions of UAVs in agriculture is to spray pesticides. The pesticides used are liquid so that when the UAV is airborne and maneuvering, the fluid experiences fluid motion or sloshing. Sloshing that occurs can cause the balance of the UAV to be disturbed. To overcome this, a bulkhead or baffle is needed in the reservoir in order to reduce fluid movement. In the case of the research studied, the simulation of sloshing in the reservoir with the presence of baffles and without the presence of baffles. This research uses different reservoir variations and different water levels, namely 55 mm, 35 mm and 15 mm. Simulations are carried out during cruising and maneuvering flights at a speed of 2 m/s. The container modeling uses the Catia V5R20 software and the simulation uses the Ansys 14.5 software. The simulation results show that the effect of baffle placement is more visible if the baffle is placed in the xy plane, while for the baffle placement in the yz plane, the force caused by sloshing is greater. In spraying the UAV-Sprayer will more often fly forward (cruise), while for maneuvers (right or left) it is only done occasionally/not too often. So that giving baffles is more effective in the xy plane because it can reduce sloshing better than the baffles in the yz plane.

DEVELOPMENT AND RESEARCH OF THE TOPOLOGY OF COOLING BAFFLES FOR BLADES OF THE AXIAL CARBON DIOXIDE TURBINES

Currently, there is an increase in average annual temperature and climate change across the various continents. Carbon dioxide emissions from energy facilities contributed to this condition. Implementation of oxy-fuel cycles is a promising solution for reducing carbon dioxide emissions from the energy sector. To date, the most efficient oxy-fuel cycle is the Allam cycle. In this cycle supercritical carbon dioxide acts as a working fluid of the cycle, wherein СО2’s temperature upstream of the turbine is 1,150 °С and the pressure is 30 MPa. Due to the high temperature of the working fluid, it is necessary to cool first stages of the carbon dioxide turbine. The feature of considered cooling system in this turbine is that carbon dioxide being used as a refrigerant too. This paper investigated two topologies of convective cooling systems in the carbon dioxide turbine’s nozzle blade as well as considers an option for increasing the intensity of heatexchange through the use of helical ribbing in the cylindrical cooling baffle. Numerical simulation involving the ANSYS software package was performed for two topologies of the cooling baffles arrangement in the nozzle blade body: configuration 1 -with 17 baffles of 1 mm diameter, configuration 2 -with three baffles of the blade profile shape. Configuration 1 proved to be more efficient: the Nusselt number has a value of 117, and average value of the heat transfer coefficient on the refrigerant side is 6,413 W/m2∙K. The effect of using helical ribbing in the cooling cylindrical baffle of the blade under study was investigated, which enabled to reduce the metal temperature by 54 °С on average and doubled the heat transfer coefficient.

Numerical simulation of sloshing flow in a 2D rectangular tank with porous baffles

Liquid sloshing in partially filled tanks can cause the structural damage and system instability in multiple fields, especially for the ocean transportation system. To improve the efficiency of anti-sloshing and wave-damping in the tank, the porous structures can be adopted. In this study, the porous media theory is applied to simulate the porous baffles for analyzing the influence of the porous baffles on the sloshing flow due to a roll motion. The numerical model of porous baffles is firstly validated by comparing with the dam-breaking and sloshing experiment, and then the effects of the baffle arrangement and excitation frequencies on the wave damping performance are analyzed in detail. It was found that the porous baffle has a poor wave-damping performance when the excitation frequency is close to the first-order natural frequency. The wave damping performance can be enhanced by increasing the height of the baffle and decreasing the porosity coefficient of the baffle, and moving the porous baffle to the water surface.

ASSESSMENT OF FLOW CHARACTERISTICS ALONG THE HYDRAULIC PHYSICAL MODEL OF A DAM SPILLWAY

Water flowing over a spillway has a very high kinetic energy because of the conversion of the entire potential energy to kinetic energy. This circumstance results in damage or significant erosion at the toes of the spillways, weir bed, and downstream of a river. To solve this problem, the water flow velocity must be minimised. Physical modelling was implemented to this conundrum in order to modify the current energy dissipating structure, the stilling basin, to enhance energy dissipation as much as achievable by downstream velocity reduction. Baffle blocks were adopted as the modification in this study because these are widely used to stabilize the jumps, shorten its length, and maximize energy dissipation. A selection of baffle arrangements was evaluated by positioning them in the stilling basin’s mid-span to identify the most effective outcome in minimizing downstream velocity. From the findings, it was clearly shown the arrangement of baffles blocks at the stilling basin impacts velocity reduction in various discharge cases. The formation of cross-waves was also assessed at the discharge channel at every discharge value with its relative distance from the sump and the width of the channel prior to the site. For discharge situations of 70.0 L/s and 100.0 L/s, modifications to the Type II stilling basin were recommended. Furthermore, constriction, expansion, or curvature should be avoided in chute spillways identical to the dam spillway to limit cross-wave generation and other unfavourable flow behaviours

Flash Smelting Settler Design Modifications to Reduce Copper Losses Using Numerical Methods

A mathematical modeling approach was used to test different design modifications in a flash smelting settler to reduce the copper losses in slag, which is economically disadvantageous for copper processing using the pyrometallurgical route. The main purpose of this study was to find ways to reduce copper losses in slag by improving the settling and coalescence of copper matte droplets, in particular, the smallest droplet sizes of ≤100 µm. These improvements inside the flash smelting (FS) settler were targeted through different settler design modifications. Three different design schemes were tested using the commercial computational fluid dynamics (CFD) software, Ansys Fluent. These settler design modification schemes included the impact of various baffle types, positioning, the height inside the settler, and settler bottom inclinations. Simulations were carried out with and without coalescence and the results were compared with normal settler design. The results revealed that the settling phenomenon and coalescence efficiency were improved significantly with these design modifications. It was concluded that a single baffle design was optimal for reducing copper losses and increasing coalescence efficiency instead of using multiple baffle arrangements. The top-mounted baffle outperformed the bottom-mounted baffle and inclined settler design.

CFD based analysis of chlorination contact tank design

Chlorination is the most widely used technique for disinfecting water. Disinfection by chlorination inactivates pathogenic micro-organisms, preventing water-borne diseases. The design of a chlorination contact tank (CCT) requires precise residence time during which the chlorine passes through the tank and the consumption of a substantial quantity of chlorine during the disinfection process. The arrangements of baffles, as well as the inlet–outlet configurations, are also important which leads to the formation of a complex flow pattern causing the short-circuiting of the fluid flow and dead zone formation inside the CCT. Short-circuiting results in inefficient mixing, whereas, dead zones indicate the presence of residual chlorine in the tank. The objective of the present work is to report the preliminary results of the Computational Fluid Dynamics (CFD) analysis undertaken to investigate the hydrodynamics, turbulent transport and mixing inside the chlorination tank. Two different types of CCT geometry (rectangular and spiral) are considered for comparing the hydraulic and mixing efficiencies. Two-dimensional steady-state and time-variable numerical simulations are carried out. Species Transport modelling provides the distribution of residence time as well as chlorine concentration inside the tank. The presence of recirculation and dead zones in the chlorination tank are analysed from the velocity contour using image analysis. It was observed that amount of dead zones is significantly higher in the case of a rectangular tank when compared to a spiral one. Different hydraulic and mixing indexes were analysed in this study to compare the disinfection efficiency of the two tanks. The presence of secondary flow due to the centrifugal force facilitates the mixing process in spiral tanks.

Analysis of the performance of the shell and tube heat exchanger: Influence of the baffles and the position of fluid inlet and outlet

The constant need for heat exchangers that are easy to manufacture and maintain, and that have a standardized and already known manufacturing technology, has led to the fact that shell and tube heat exchangers are one of the most common devices used in the process industry. In this paper, the analytical and numerical models of the basic shell and heat exchanger have presented with dimensions of 3750 x 1000 mm and a nominal heat capacity of 410 kW. Using the flow simulation, the influence of different numbers and arrangement of baffles and the changing the position of the inlet and outlet of warmer fluid are considered. The temperatures of the fluids on the inlet and outlet are taken into account as the main parameters for heat exchanger performance. From obtained results, it can be concluded that with the increase in the number of baffles, the performance of the heat exchanger is increased. The position of the inlet and outlet of the warmer fluid greatly influence the heat exchanger performance.

Study of Baffles Arrangement Influence on the Natural Convection into a Heated Square Channel

Study of Baffles Arrangement Influence on the Natural Convection into a Heated Square Channel

INFLUENCE OF DIFFERENT TYPES OF BAFFLE ARRANGEMENT AND SPACING ON HYDROTHERMAL FLOW PHENOMENA OVER A RECTANGULAR CHANNEL

INFLUENCE OF DIFFERENT TYPES OF BAFFLE ARRANGEMENT AND SPACING ON HYDROTHERMAL FLOW PHENOMENA OVER A RECTANGULAR CHANNEL

Optimization of the Internal Circulating Fluidized Bed Using Computational Fluid Dynamics Technology

The computational fluid dynamics (CFD) technology is analyzed and calculated utilizing the turbulence model and multiphase flow model to explore the performance of internal circulating fluidized beds (ICFB) based on CFD. The three-dimensional simulation method can study the hydrodynamic properties of the ICFB, and the performance of the fluidized bed is optimized. The fluidization performance of the ICFB is improved through the experimental study of the cross-shaped baffle. Then, through the cross-shaped baffle and funnel-shaped baffle placement, the fluidized bed reaches a coupled optimization. The results show that CFD simulation technology can effectively improve the mass transfer efficiency and performance of sewage treatment. The base gap cross-shaped baffle can improve the hydraulic conditions of the fluidized bed and reduce the system energy consumption. The cross-shaped baffle and funnel-shaped baffle can perfect the performance of the reactor and effectively strengthen the treatment in the intense aerobic process of industrial sewage.

Optimal design of vertical porous baffle in a swaying oscillating rectangular tank using a machine learning model

The sloshing-induced impact loads on the tank wall are significant when the liquid in a tank is excited at and around its natural frequencies, which are highly reliant on the tank's geometry and liquid fill level. Herein, To design the optimal porous baffle for mitigation of liquid sloshing, a machine learning algorithm based on the MLPR model is adopted. First, a sloshing database comprising of different features such as porosity, baffle arrangement, submergence depth of the baffle, motion period, and free-surface elevation at the tank wall is prepared from the sloshing experiments in a swaying rectangular tank with the vertical porous baffle. Then, the detailed feature study is conducted on the database. The MLPR model is trained and validated after preprocessing the data, and the predictions on the free-surface elevation are made for 3520 combinations of feature values using the trained model. A comparison with the available experimental data shows that a well-trained machine learning model can predict well the physical characteristics that occurred in a sloshing tank. A fully submerged single baffle with a porosity of 0.1375 is obtained as the optimal baffle. It reduces significantly the liquid sloshing at resonance, especially the first-mode resonance peak, compared to the no-baffle tank.

Experimental and Numerical investigation of implementing a novel vortex generator: A Perforated Delta Wing Vortex Generator (PDWVG) on the performance of Solar Air Collector

Experiments were carried out for the numerical investigation of heat transfer enhancement in a solar air collector using different types of baffles and vortex generators. In this study, the vortex generator was implemented to increase the efficiency of the solar air collector. The variations in Nusselt number, pressure drop, friction coefficient, thermal and exergy efficiency in four collectors with different baffles arrangement (type A, B, C, D) were investigated. Type A was chosen as the optimum collector for implementing the vortex generator on the absorber surface. In the solar air collector the effects of using a novel vortex generator - the Perforated Delta Wing Vortex Generator (PDWVG), in comparison with a flat one - the Flat Delta Wing Vortex Generator (FDWVG), were considered. In order to determine the maximum efficiency of the solar air collector, four different pitch ratios of vortex generators were studied. The Nusselt number and pressure drop increased with Reynolds number but the friction coefficient decreased with Reynolds; the experimental and numerical results revealed that the thermal and exergy efficiency decreased from a specific range. The comparison of PDWVG and FDWVG showed that presence of holes on the novel vortex generator, led to reduced pressure drop and increased the heat transfer between the air flow and the absorber surface. Increasing the number of vortex generator rows had a slight effect on increasing the studied parameters. The results showed that collector type A with ep=0.55 of PDWVG improves the energy and exergy efficiency 4.43% and 5.29% respectively.

Numerical and experimental study of anti-slosh performance of combined baffles in partially filled tank vehicles

A numerical model based on VOF (Volume of Fluid) method is established to analyze liquid sloshing phenomenon in a partially filled cylindrical tank with or without various baffle arrangements. A series of slosh experiments were conducted on a scaled tank under harmonic acceleration excitations. The model is validated by comparing the slosh responses in terms of forces and moments with the measured data. The validated model is further employed to investigate the effect of combined baffles—proposed in the paper—on liquid sloshing motion. The results imply that conventional baffles could only limit liquid slosh in the longitudinal direction. The addition of combined baffles could suppress liquid slosh in both the longitudinal and lateral directions and the braking performance and roll stability limits of tank vehicles are thus improved.

The use of passive baffles to increase the yield of a single slope solar still

Despite their relative simplicity, single slope solar stills remain one of the most viable solutions to the production of freshwater from saline and non-potable water sources. Over the years, numerous researchers have attempted to improve the yield of single slope solar stills through changes to their geometry and the use of various design modifications. Despite this long history of research, one modification that has not been fully explored is the use of passive baffles to alter the natural convection inside them.Though baffles have frequently been used to suppress natural convection in enclosures, there may also be the opportunity to use them to enhance natural convection. This judicious placement of baffles to enhance the natural convection could potentially improve the yield from single slope solar stills, however it has not been well explored in the literature.To address this issue, this work examined the effect of vertically mounted passive baffles on the natural convection inside a single slope solar still geometry. In this vein, a computational fluid dynamics simulation was conducted for a still containing a baffle, with the results validated experimentally using particle image velocimetry. On this basis, subsequent simulations explored the effect of baffle length and position on stills with cover angles from 10–60°. The results showed that baffles did have a marked influence on the natural convection flow field and could increase the natural convection heat transfer coefficient, which is directly proportional to a solar still’s yield, by up to 20%.It was also found that short baffles enhanced natural convection at low cover angles, while baffles mounted close to the front of a still provided an improvement to the transfer processes over the widest range of conditions. Finally, the work led to the development of a relationship to describe the effect of baffles on natural convection, as shown in Equation (1), that it is hoped will aid designers of single slope solar stills in the future.(1)Nu'=Ra'0.188∗AR-0.29∗cosθ-0.5∗bB0.08∗dD0.09

An experimental research on the net output power and current density distribution of PEM fuel cells with trapezoid baffled flow fields

The net output power and current density distribution uniformity of proton exchange membrane (PEM) fuel cells are particularly important evaluation criteria in the flow field design. In recent years, the flow field with baffles has become research hotspots, and the trapezoid baffled flow field has been proved to increase the performance of fuel cells. However, most of the research studies only stay at the level of single flow channel simulation and little experimental data on the flow field of the entire bipolar plate. In this study, the performance, pressure drop, and current density distribution of PEM fuel cells with different baffled flow field plates are tested experimentally. The results indicate that adding baffles in the conventional parallel flow field can significantly improve the output performance and current density distribution uniformity of the fuel cell, and the improvement effect is better with the increase in baffle height. However, increasing the baffle height will inevitably raise the pressure drop of the flow field. To solve this problem, the flow field with a half baffle arrangement is innovatively designed. The proposed half-baffled flow field can keep the uniformity of current density distribution and reduce the pressure drop at the same time. This method provides a new inspiration for the design of the flow field.

Design and simulation investigation of variable period passive anti-rolling tank

Objectives Aiming at the characteristics of semi-submersible vessels with large roll period changes under different working conditions, a passive controllable anti-roll tank with an adjust able harmonic period is designed. The harmonic period is changed by controlling the height of the T-shaped baffle in the tank, generating a better anti-roll effect that matches the ship's roll period. Methods First, the influence of the T-shaped baffle arrangement on the harmonic period of the tank is analyzed though Computational Fluid Dynamics software, and the design of the tank is optimized. Second, in order to adapt to semi-submersible vessels under different working conditions or encountering waves of different frequencies, the auto-regressive (AR) model is used to predict the ship's roll period and adjust the number of raised baffles according to the prediction, on the basis of which the designed water tank is simulated. Results The simulation results show that the designed anti-roll tank can adapt to the different working conditions of semi-submersible vessels with positive effects. Conclusions Changing the number of T-shaped baffles can increase the harmonic period of the tank to a certain extent, and it can be set to match the roll period of the semi-submersible vessel by controlling the baffles, thereby better adapting to ships with large roll period changes and providing strong anti-roll ability.

Effects of baffle on cycle‐to‐cycle variation in stirred vessel driven by paddle turbine using quadruple proper orthogonal decomposition

AbstractThe flow of stirring process is complex and multiscale. To analyze the effects of baffle on the flow characteristics driven by paddle turbine, particle image velocimetry (PIV) experiments were performed for the unbaffled stirred vessel and the standard baffled stirred vessel stirred by the single paddle turbine. Under the baffle arrangement, the flow discharge was strengthened, and the range of high‐velocity region was obviously expanded, and the velocity significantly fluctuated near the blade. The swirling intensity behind the blade decreased significantly, and no significant wake structure was formed, thereby helping reduce the local velocity difference attributed to the wake structure and facilitate the uniform mixing of materials. The instantaneous velocity field was decomposed into four parts at different scales by employing quadruple Proper Orthogonal Decomposition method. The quantitative analysis of different scale flow structures in stirred process was realized. Under the baffle arrangement, the flow process was facilitated in the measurement plane. In addition, the fluctuation velocity increased significantly, and the mass transfer was enhanced by vortex motion of the fluid elements, which was conducive to the uniform mixing of materials.