Porous Baffles Research Articles

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.

Performance and Parameter Sensitivity Analysis of the PEMFC Flow Channel with Porous Baffles

In this paper, a method to improve the performance of PEMFCs using porous material as a flow channel baffle is proposed. The results show that PEMFCs with four porous baffles flow channels have better performance at high current density compared with the traditional flow channel. The structural parameters of the flow channel explored in this study include porosity, the thickness of the baffle and the number of baffles, and their influence on the performance of PEMFCs. Sensitivity analysis results show that the performance of the PEMFCs with the porous baffle channel is the most sensitive to baffle thickness, and the thickness and baffle could be appropriately adjusted. The number of plates and porosity of the baffle are adjusted to improve the performance of the PEMFCs.

Numerical study on modelling perforated elements using porous baffle interface and porous region

PurposeThis study aims to analyze simplified methods for modelling the flow through perforated elements (i.e. porous baffle interface and porous region), searching for a faster and easier way to simulate these components. The numerical simulations refer to a muffler geometry available in literature as a case study.Design/methodology/approachThe installation of scrubber onboard ships to satisfy the International Maritime Organization emissions regulations is a reliable and efficient solution. However, scrubbers have considerable dimensions, interfering with other exhaust line components. Therefore, scrubber installation in the funnels requires integration with other elements, for example, silencers. Perforated pipes and plates represent the main elements of scrubber and silencers. The study of their layout is, therefore, necessary to reduce emissions and noise. Numerical simulations allow evaluating the efficiency of integrated components.FindingsThe study highlights that velocity and pressure predicted by the simplified models have a strong correlation with the resistance coefficients. Even though the simplified models do not accurately reproduce the flow through the holes, the use of such models allows a fast and easy comparison between concurrent muffler geometries, giving aid in the early design phases.Originality/valueThe lack of general guidelines and comparisons in the literature between different modelling strategies of perforated elements supports the novelty of the present work and its impact on design applications. Study the flow inside scrubbers and mufflers is fundamental to evaluate their performances. Therefore, having a simple numerical method is suited for industrial applications during the design process.

Numerical Investigation of Simultaneous Effects of Nanofluid Flow and Porous Baffle on Thermal Energy Transfer and Flow Features in a Circular Channel

Abstract In the present work, the forced-convection heat transfer features of different nanofluids in a circular channel with porous baffles are numerically investigated. Nanofluid flow in the porous area is simulated by the simultaneous use of Darcy-Brinkman-Forchheimer and two-phase mixture models. The flow is considered to be laminar, two-dimensional, steady, axially symmetric, and incompressible. The simulations are conducted in fluent software and by using the finite volume method and SIMPLE algorithm. The influences of various parameters, including Reynolds number, volume fractions of nanoparticles, Darcy number, porous region height, and various nanofluid types on the nanofluid flows and their thermal energy transfer features, are investigated. Results show that porous blocks significantly change the flow characteristics and thermal energy transfer features. For instance, at low Darcy numbers, the permeability of the porous region decreases, and the porous baffles have greater resistance against the nanofluid flow. As a result, the vortex area becomes stronger and taller, and streamlines near obstacles are tighter. However, in high Darcy numbers, due to the high permeability of the porous medium, the flow will be the same as the flow in the channel without barriers, and the porous baffles will not have much influence on the flow. For example, at Darcy number Da = 10−4 the vortex area almost disappears. The growth of conductivity ratio increases the local Nu in the vicinity of the barriers. Properties of the porous medium and nanofluid flow affect the thermal energy transfer rate, and it can be improved by making appropriate changes to these features.

Anti-slosh effect of a horizontal porous baffle in a swaying/rolling rectangular tank: Analytical and experimental approaches

The horizontal porous baffle and its effect as an anti-slosh device have been investigated intensively in a swaying and rolling rectangular tank. To accurately assess the level at which porous baffles reduce liquid sloshing, the Matched Eigenfunction Expansion Method (MEEM) has been utilized as an analytical tool. The velocity potentials in the horizontal baffle-covered fluid region are expressed by the sum of the homogeneous and particular solutions to avoid solving the complex dispersion equation. By applying an equivalent linearized quadratic loss model, the nonlinear algebraic equation is derived and solved by implementing the Newton–Raphson iterative scheme. To prove the validity of the present theoretical model, a series of experiments have been conducted with different centered horizontal porous baffles with varying porosities and submerged depths in a swaying and rolling rectangular tank. Reasonably good agreements are obtained regarding the analytical solutions and the experiment's findings. The influence of porosity, submerged depth, and length of a centered horizontal porous baffle on anti-slosh performance have been analyzed, especially at resonance modes. The developed predictive tool can potentially provide guidelines for optimal design of the horizontal porous baffle.

Numerical Analysis of Enhanced Heat Transfer Using a Pair of Similar Porous Baffles in a Backward-Facing Step Flow

Numerical Analysis of Enhanced Heat Transfer Using a Pair of Similar Porous Baffles in a Backward-Facing Step Flow

Finite element method for analyzing effects of porous baffle on liquid sloshing in the two-dimensional tanks

Purpose The purpose of this paper is to analyze the liquid sloshing behaviors in two-dimensional tanks with various porous baffles under the external excitation. Design/methodology/approach Adopting the finite element method (FEM) and control variable method to study the impacts of the height, length, number, location, shape, porous-effect parameter of the porous baffle, the external load frequency and the shape of the tank on the liquid sloshing response. Findings The amplitude of the free surface can be reduced effectively when the baffle opening is appropriate. The anti-sway ability of the system increases in pace with the baffle’s height growing. Under the same conditions, the shapes of the baffles have an important effect on improving the anti-sway ability of the system. Originality/value As there exist the differences of the velocity potential between each side of the porous baffle, which means that there are two different velocity potentials at a point on the porous baffle, the conventional finite element modeling technologies are not suitable to be applied here. To deal with this problem, the points on the porous baffle are regarded as two nodes with the same coordinate to model and calculate.

The influence of obliquely perforated dual-baffles on sway induced tank sloshing dynamics

This paper examines the influence of oblique perforated baffles on the sloshing dynamics of rectangular liquid storage tanks. The analysis presented accounts for sway induced hydrodynamic forces and entropy generation. Internal liquid free surface oscillation is modelled by the volume of fluid method. The effect of baffle geometric parameters, orientation and porosity on loads is examined and numerical results are compared against a set of experiments. Consequently, an engineering method suggesting the optimum size, angle of inclination and topology of baffles for the case of a rectangular tank is presented. It is shown that implementation of optimized oblique porous dual baffles may reduce sloshing loads by up to 15%.

Anti-sloshing effects of a vertical porous baffle in a rolling rectangular tank

The anti-sloshing effects of a vertical porous baffle placed at the center of a rolling rectangular tank have been investigated rigorously. The potential-based analytical solutions were developed using the matched eigenfunction expansion method (MEEM) with an equivalent linearized quadratic loss model. For this, the empirical formula of the drag coefficient was obtained through the curve-fitting with the CFD results for the channel flow with a circular void hole. In parallel with the analytical model, a 3D implicit turbulent model based on incompressible unsteady Reynolds-averaged Navier–Stokes (RANS) equations was used with the volume of fluid (VOF) multiphase model. To validate the analytical and numerical model, experiments were conducted in a rolling rectangular tank with a fully/partially submerged porous baffle of different porosities. The acceptability and limitation of the present analytical model was quantified and qualified using experimental and numerical approach. The presented analytical and 3D turbulent numerical model will provide a mutually complementary tool for the understanding of the energy dissipation mechanism and efficient design of the porous baffle as an anti-sloshing device.

Shape optimization of segmental porous baffles for enhanced thermo-hydraulic performance of shell-and-tube heat exchanger

This study presents the development and evaluation of a novel shell-and-tube heat exchanger (STHX) design with segmental porous baffles. Computational fluid dynamics (CFD) in combination with machine learning tools are utilized to investigate the thermo-hydraulic impacts of segmental porous baffles on shell side flow of a STHX. Three geometric parameters (number of baffles, baffle angle, and baffle thickness) of these baffles, which are placed inside the STHX, are selected to perform the parametric study and multi-objective optimization. Higher number of baffles are beneficial to increase the rate of heat exchange; however, it would escalate the pressure drop considerably. Results also show that baffles angle plays a critical role on the performance of a STHX. An artificial neural network (ANN) is trained to predict the system’s performance. As lowering the pressure drop and increasing the heat transfer are the two main objectives in STHX, a multi-objective optimization study is conducted. Different decision-making algorithms are also applied to find the best alternative among the Pareto frontier points. Results of optimization show that a STHX with 10 porous baffles, baffle angle of 111.9, and baffle thickness of 16.69 mm would be the best geometrical configuration which results in a heat transfer rate of 523.81 kW while the pressure drop of the shell side flow would be 48.87 kPa. With this novel design, it is also possible to improve both pressure drop and heat transfer rate of STHX, simultaneously. A particular configuration of the introduced STHX could reduce the pressure drop by 61.3% while heat transfer enhances by 11.15% simultaneously.

Performance assessment of porous baffle on liquid sloshing dynamics in a barge carrying liquid tank

ABSTRACT A comprehensive experimental work is done to investigate sloshing dynamics in a partially liquid-filled baffled tank, equipped with a floating barge. An aspect ratio(hs /l, liquid depth, hs to length of tank, l) of 0.488 (above critical fill level), which corresponds to 75% fill level, is considered. The barge was subjected to regular wave excitations with a wave height of 0.1 m and frequencies ranging from 0.45Hz to 1.54Hz under beam sea condition. In addition, porous baffles are placed inside a rectangular tank to study its effectiveness in reducing the sloshing energy. Three different porosities of 15%, 20.2% and 25.2% at l/2 are considered. The effectiveness of baffles is explored and the salient results for a single porous baffle are discussed. It is learnt that the effect of baffles on sway and roll responses is significant, whereas it is insignificant on heave. Porous baffles are effective in suppressing the sloshing oscillation in the vicinity or at wave excitation, fw =f 1, whereas the sloshing is amplified at fw =f 2 and fw =f 3 due to the resonance condition of modified natural frequencies.

Effect of porous baffle on sloshing pressure distribution in a barge mounted container subjected to regular wave excitation

An experimental study has been carried out to assess the sloshing pressure expected on the side walls of the tank and on top panel. A liquid fill level with an aspect ratio (hs /l, where hs is the static liquid depth and l is the tank length) of 0.488 is considered which corresponds to 75% liquid fill level. In view of suppressing sloshing oscillation and consequent sloshing pressure, the baffle wall configurations such as porous wall at l/2 and porous walls at l/3 and 2l/3 were adopted. Three porosities of 15%, 20.2%, and 25.2% were considered. The sloshing tank is fitted into the freely floating barge of model scale 1:43. The barge is kept inside the wave flume in the beam sea conditions. The effects of wave excitation frequencies and on the sloshing pressure variation have been studied in detail. For comparison purpose, solid wall placed at l/2 (Nasar and Sannasiraj, 2018) is also considered and, the salient results are herein reported.

Assessment and optimization of exhaust gas heat exchanger with porous baffles and porous fins

The shell and tube heat exchanger with segmental baffles is widely applied in industry owing to its low cost and easy maintenance. However, when adopted it as the exhaust heat exchanger in engine waste heat recovery system, the large pressure drops on shell side and low thermal efficiency greatly affect the efficiency of the whole system. To overcome the aforementioned shortcomings, a structure of shell and tube heat exchanger with porous baffles and porous fins is put forward and numerically analyzed in this study. Comparisons on the pressure drop, heat transfer and comprehensive performance are firstly conducted between the proposed heat exchanger and other five heat exchangers with different structures. The results show that adding porous baffles and porous fins can increase heat transfer by 92.14%, decrease pressure drop by 64.70%, and reduce weight by 11.35% under the mass flow rate is 0.1280 kg/s, hence the proposed heat exchanger owns the best overall performance among six heat exchangers. Subsequently, the effects of key design parameters (fins number per meter, inner tube pitch and porosity) on the performance of the proposed heat exchanger are analyzed and optimized by artificial neural network and genetic algorithm to achieve the best for comprehensive performance. The results are as follows: when the above three parameters are 94 m−1, 58.6 mm and 0.702 respectively, the performance achieved the best.

Experimental and Numerical Evaluation of a Porous Baffle Design for Contact Tanks

AbstractIn water treatment plants, the design of contact tanks is of critical importance for effective disinfection of potable water. The most important design problem in these flow-through systems...

A Design for Vortex Suppression Downstream of a Submerged Gate

Interaction of recirculating and mean flow downstream of a submerged gate may form significant vortex structures, which may affect the stability of the gate. Although these flow structures that appear in submerged hydraulic jumps received considerable attention in the literature, relatively less work was devoted to the analysis and suppression of the vortex structures downstream of a submerged gate. In this work, internal flow structure and vortex dynamics around a submerged gate were investigated through laboratory tests and large-eddy simulation (LES) using computational fluid dynamics (CFD). It is shown that numerical results obtained for mean velocity field are in good agreement with the experimental measurements. A helical vortex pair connected with a horseshoe vortex system was identified within the roller region using high-resolution numerical simulations. Damping performance of different types of anti-vortex elements placed on the downstream face of the gate are evaluated based on numerical studies. It is shown that the horizontal porous baffle mounted at an elevation below the free surface reduced the vortex magnitudes in the roller region by 26.8%. With the implementation of the proposed vortex breaker, lift forces acting on the gate lip were reduced by 9.4% and drag forces acting on the downstream face of the gate were reduced by 8.6%. Finally, in this study, we assess the performance of the vortex breaker under different flow conditions.

Enhanced heat transfer and flow analysis in a backward-facing step using a porous baffle

The backward-facing step or the sudden expansion in internal flows is an important problem in different areas. In this study, a porous baffle is mounted on the opposite wall of a sudden expansion to enhance heat transfer near the step. Unlike the solid baffle, which is extensively studied in the literature, the porous baffle has a lower pressure drop, and its properties can be tuned to reach the optimal prospected performance. Effects of different porous baffle geometrical parameters including its normalized height (Hb = 0.5, 1.0, 1.5, 1.75), width (Wb = 0.5, 1, 1.5, 2.0, 2.5), porous baffle-step relative distance (D = 1, 2, 3, 4), Darcy number (10−2, 10−3, 10−4, 10−6), and Reynolds number (100, 200, 300, 400, 500) on the heat transfer and pressure drop are investigated. The simulation indicates that higher Reynolds numbers enhance more the heat transfer (35% improvement at Re = 500 with respect to 10% at Re = 100). Also, longer baffles can lead to higher heat transfer rates (5% improvement in Hb = 0.5 with respect to 32% at Hb = 1.5).

A NURBS-based isogeometric boundary element method for analysis of liquid sloshing in axisymmetric tanks with various porous baffles

An isogeometric boundary element method (IGA-BEM) based on the non-uniform rational B-splines (NURBS) is firstly performed to investigate the liquid sloshing in axisymmetric tanks with the porous baffles. The proposed method can completely maintain the advantages of the BEM that only the boundary of a domain requires discretization. By applying the NURBS basis functions it can exactly describe the geometry of the boundary. Meanwhile, it can also be obtained better solution field approximation at the domain boundary. Furthermore, as to the axisymmetric geometries of the containers considered in this paper, the 3-D liquid sloshing problems can be effectively reduced to 2-D ones on half of the cross-sections of the containers, which can significantly increase the computational efficiency. Meanwhile, the zoning method is employed in this paper to treat the arbitrary mounted porous baffles, and the Laplace equation is utilized as the governing equation of the potential flow model by assuming the fluid motion to be inviscid, irrotational and incompressible. Additionally, the weighted residual method together with the Green’s theorem is applied to develop the BEM integral equation. The natural sloshing frequencies and dynamic sloshing forces solved by the proposed method are compared with the available literatures and the traditional boundary element method (BEM). Good agreements are observed in the comparisons between numerical results and those of the existing literatures. And higher accuracy and convergence can be achieved by the proposed IGA-BEM method with significantly fewer nodes than the traditional BEM. Moreover, spherical tanks with the coaxial hemispherical, wall-mounted conical or surface-piercing cylindrical porous baffle, ellipsoidal tanks with spheroidal or surface-piercing cylindrical porous baffle, and the toroidal tank with tubular porous baffle are considered to investigate the effects of the porous-effect parameter, radius, length, height, horizontal and vertical semi-axes of the porous baffle on the sloshing characteristics (i.e. dynamic sloshing forces and surface elevations). The results show that the surface-piercing cylindrical porous baffle offers more noticeable suppression on sloshing response than the hemispherical and spheroidal porous baffles. Changing the radius of the tubular porous baffle has almost negligible effect on the sloshing force acting on the toroidal tank. The excitation frequency corresponding to the maximal value of sloshing force can be altered evidently by changing the porous-effect parameter of the porous baffle. In addition, choosing reasonable porous-effect parameter, radius, horizontal semi-axes and relatively larger length, height as well as vertical semi-axes for the porous baffles yields considerable suppression on the sloshing response.

Design and Verification of Tuned Liquid Column Dampers for High-rise Buildings Using CFD

BMT Fluid Mechanics conducted a comprehensive flow study on the effectiveness of a pair of Tuned Liquid Column Dampers (TLCDs) aimed at mitigating wind-induced accelerations in a high-rise building. The study successfully combined Computational Fluid Dynamics (CFD) with physical model tests performed at the 6 degree-of-freedom shake table facility located at the Department of Civil Engineering of the University of Bristol. The original TLCD concept discussed in this work was proposed at the early design stages of a slender 42-storey high-end residential building located in the Middle East. On-site full-scale measurements and High Frequency Force Balance (HFFB) wind tunnel tests performed by BMT Fluid Mechanics showed that the highest occupied floors could experience excessive wind-induced motion. Depending on the inherent damping of the finished structure, this motion had the potential to exceed standard occupant comfort criteria. A new CFD methodology was developed to assess the performance of the TLCD design using the multi-phase Volume-of-Fluid (VOF) solver and dynamic mesh motion libraries available in the CFD software tool HELYX®. The damping effects introduced by the array of internal porous baffles in the TLCD were approximated using a Darcy-Forchheimer porosity model. Comparisons of free-decay damping performance between CFD results and shake table experiments for a 1:20 scale model of a 3 baffles’ TLCD configuration were found to be satisfactory for design purposes. The results for the amplitude of the net forces acting on the TLCD, as well as the frequency response measured using the free-decay logarithmic decrement approach, confirmed that the proposed CFD methodology provides an accurate representation of real operating conditions. The same CFD approach was successfully applied to model the full-scale TLCD device. With the introduction of a pair of identical purposely designed TLCDs, a 30% increase performance of the structural response of the 42-storey building to wind loading excitation was achieved.

Thermal optimization of shell and tube heat exchanger using porous baffles

In this study, total heat transfer rate and pressure drop along a shell and tube heat exchanger (STHX) with 6 porous baffles are numerically investigated. To study the impacts of segmental porous baffles, three values for the permeability (10−9 m2, 10−12 m2, and 10−15 m2), porosity (0.2, 0.5, and 0.8), and baffle cut (25%, 35%, 50%) were considered, and the output parameters were calculated. Low baffle cuts provided the highest heat transfer; however, it generated a considerable amount of pressure drop as well. Although the porosity of 0.2 was superior in terms of heat transfer, higher pressure drop at lower baffle cut is the obstacle to consider it as the optimum value. The data was then utilized to train an Artificial Neural Network (ANN) to characterize the STHX and perform the sensitivity analysis. Baffle cut had the highest impact on the heat transfer as well as pressure drop while the porosity had the least in both by having 5% contribution. Finally, using genetic algorithm (GA), the optimum values for permeability, porosity, and baffle cut are calculated to gain the maximum heat transfer and minimum pressure drop in the system.

The experimental study of increasing the efficiency of emulsion separation

The aim of this research paper is to compare the operation efficiency of two types of coalescents: insert, made of high porous material and flat baffles. For this purpose, the method of physical experiment was applied. This research paper shows that the use of them in the settling tank allows to increase the efficiency and velocity of water-oil emulsion separation with an increase of oil concentration in the original mixture from 15 up to 25%. The experimental studies also show that the most effective coalescers are the baffles, than the inserts, made of highly porous cellular material, due to the fact that the cells are quickly clogged with heavy oil components, which leads to a more complex flow structure through them, therefore, the process of mixing oil and water compounds is intensified and prevails over the coalescence process. The velocity of oil-water emulsion separation when using the inserts, made of highly porous cellular material, and baffles in comparison with the settling tank without inserts, increases on average by 10.9 and 14.5%.