Effect Of Baffles Research Articles

Effect of Bottom Baffles and Air Inlet Position on Mass Transfer Performance of a Water-Sparged Aerocyclone

Water-sparged Aerocyclone (WSA) is a new type of gas-liquid mass transfer equipment with a coupling field of liquid jet with gas cyclone, which can be widely used in wastewater treatment process. To further optimize the structural design of WSA, the effect of bottom baffles and air inlet position on mass transfer performance of WSA was comparatively studied by air stripping of ammonia from wastewater. The results indicated that the separation space configuration of a WSA affects its mass transfer performances. Under the same condition, the axial air inlet position has no effect on mass transfer performance, but moving air inlet position downward could reduce the gas pressure drop in WSA by about 10%, which was probably caused by abating the friction loss between the gas cyclone and the wall. In case of high air inlet velocity and low liquid flow rate, the bottom baffles in the WSA could intensify the mixing effect between gas and liquid phases, thereby improving the mass transfer performance, and the effect is more pronounced with the increase of air inlet velocity. The results could be used as a guide for the design of WSA with excellent mass transfer performance.

The effect of conductive baffles on natural convection in a power-law fluid-filled square cavity

This research involves the numerical study of the conjugate natural convection of a power-law fluid in a two-dimensional square cavity with a pair of conducting baffles. The lower wall of the cavity contains a heat source with constant heat flux, while a pair of conductive baffles is embedded on its upper wall. The left and right side walls and some parts of the lower wall of the cavity are thermally insulated and its upper wall is kept at a low temperature. The governing equations along with the corresponding boundary conditions are solved using the numerical finite difference method based on the control volume formulation and SIMPLE algorithm. The effects of pertinent parameters on flow and temperature fields and heat transfer rate are investigated. From the results of the numerical solution, increasing the Rayleigh number and baffles thermal conductivity enhance the thermal performance of the cavity. So that for $$ Ra = 10^{6} , $$ with an increase in the thermal conductivity ratio from $$ 1 $$ to $$ 100, $$ the average Nusselt number increases by about 14% for both cases $$ n = 0.6 $$ and $$ n = 1.2 $$ . As well as a decrease in power-law index, except in low Rayleigh numbers, increases the heat transfer rate. Based on the results, the increase of the average Nusselt number is about 283% for a power-law index reduction in the range of $$ 0.6 \le n \le 1.2 $$ at $$ Ra = 10^{6} $$ . Also, an increase of the length of the baffles deteriorates the thermal performance of the cavity at high Rayleigh numbers, while enhances it at low Rayleigh numbers.

Effect of baffle block configurations on characteristics of hydraulic jump in adverse stilling basins

The construction of stilling basin with adverse slope change the characteristics of hydraulic jump such as sequent depth ratio, length of jump ratio, length of roller and energy dissipation ratio, consequently the dimensions of stilling basin are changed, also using baffle blocks with different configurations develop these characteristics. In this study different shapes of baffle block (models (A), (B), (C) and (D)) installed in the stilling basins at adverse slopes (- 0.03, - 0.045, - 0.06) in addition to horizontal bed, all these models are tested in the stilling basin to show their effects on the characteristics of hydraulic jump, the experiments applied for the range of Froude number (Fr1) between 3.99 and 7.48. The baffle block model (D) showed good results when compared with models (B) and (C), therefore it used with arrangement of (single and double row) and compared with baffle block model (A) at slopes (0, - 0.03, - 0.045, - 0.06) to study the effects of baffle blocks on hydraulic jump when bed slopes are changed. In general using baffle block caused a reduction in sequent depth ratio, length of jump ratio and the length of the roller, but the energy dissipation ratio increased.

Study of Shell and Tube Heat Exchanger with the Effect of Types of Baffles

For evaluation of shell and tube heat exchanger, thermal performance and pressure drop are considered as major factors. Both, thermal performance and pressure drop are dependent on the path of fluid flow and types of baffles in different orientations respectively. Increasing the complexity of baffles enhances heat transfer which also results in higher pressure drop which means higher pumping power is required. This reduces the system efficiency. This paper presents the numerical simulations carried out on different baffles i.e. single segmental, double segmental and helical baffles. This shows the effect of baffles on pressure drop in shell and tube heat exchanger. Single segmental baffles show the formation of dead zones where heat transfer cannot take place effectively. Double segmental baffles reduce the vibrational damage as compared to single segmental baffles. The use of helical baffles shows a decrease in pressure drop due to the elimination of dead zones. The less dead zones result in better heat transfer. The lower pressure drop results in lower pumping power, which in turn increases the overall system efficiency. The comparative results show that helical baffles are more advantageous than other two baffles.

Sloshing of liquid in partially liquid filled toroidal tank with various baffles under lateral excitation

A technique to study effect of various baffles on liquid oscillations in partially filled rigid toroidal tanks is first developed by extending the semi-analytical scaled boundary finite element method (SBFEM), which utilizes the advantages of both the boundary element (BEM) and finite element methods (FEM). As found in the BEM, only the boundary is discretized to reduce the space by one, and no fundamental solution is needed unlike the BEM. The calculated liquid domain is divided into several simple sub-domains so that the liquid velocity potential in each liquid sub-domain becomes the class C1 with continuity boundary conditions. Based on the linear potential theory and weighted residual method, the semi-analytical solutions of the liquid velocity potential corresponding to each sub-domain are obtained by means of SBFEM, where the geometry of each sub-domain is transformed into scaled boundary coordinates, including the radial and circumferential coordinates by using a scaling centre, and the finite-element approximation of the circumferential coordinate yields the analytical equation in the radial coordinate. By discretizing the flow boundaries, the integral equation governed on the boundary is formulated into a general matrix eigenvalue problem. Based on the eigenvalue problem and multimodal method, an efficient methodology is adopted to computer the sloshing masses and sloshing force. Accuracy, simple and fast numerical computations are observed by the convergence study, and excellent agreements have been achieved in the comparison of results obtained by the proposed approach with other methods. Meanwhile, several baffle configurations are considered including the horizontal bottom-mounted and surface-piercing ring baffles as well as their combination form, bottom-mounted and surface-piercing ring baffles as well as their combination, and free surface-touching baffles. The effects of baffled arrangement, the ratio b/a of elliptical cross section, liquid fill level, and baffles' length upon the sloshing frequencies, the associated sloshing mode shapes and sloshing forces are investigated in detail and some conclusions are outlined. The results show that the present method allows for the simulation of complex 3D sloshing phenomena using a relative small number of degrees of freedom while the mesh consists of two-dimensional elements only.

Three-dimensional numerical investigation of flow through screens as energy dissipators

Screens, perforated units to dissipate energy in hydraulic structures, are investigated numerically in this study. These units are part of a physical setup exposed to supercritical flows, normally created by sluice gates. The interaction of perforated screens and supercritical flows results in local complex three-dimensional flows, which can be analyzed by the application of RANS-based flow equations. The most important controlling parameters include supercritical Froude number between 2 and 10 and screen porosity of 40% and 50%. Numerical water surface profiles and energy dissipation are validated by the author’s experimental data. This paper derives a set of equations in terms of depth ratio of the hydraulic jump through the perforated screens and assesses the effect of baffles on energy dissipation. This study seeks a proof-of-concept for the application of the RANS-based technique for further application of the result to real hydraulic structures in due course.

Effect of baffles on performance of fluid catalytic cracking riser

Increasing demand of automobile fuel and a need to process heavier crude oil makes it imperative to find improvements to the design of existing fluid catalytic cracking (FCC) units. Several modifications to the design of the riser section of FCC units have been suggested in previous studies including: improved feed nozzle designs, multiple nozzle configurations, internal baffles, and novel two-stage-riser systems. In this study, we investigate the effects of baffles on the performance of FCC risers using computational fluid dynamics simulations. In this study, predictions from a basis model (without baffles) are compared with those from four different configurations including: (i) 5-cm baffles at 5-m spacing, (ii) 7.5-cm baffles at 5-m spacing, (iii) 10-cm baffles with 5-m spacing, (iv) 10-cm baffles at 2.5-m spacing, and (v) 10-cm baffles at 1-m spacing. The baffles force the catalyst away from walls toward the center of the riser, enhancing the radial dispersion of the catalyst and the heat transfer inside the riser. The use of longer baffles and smaller spacings further increases the dispersion, yielding more homogeneous radial profiles. The changes in the radial dispersion result in variations in the conversion, yields, and pressure drops. The baffles increase conversion of vacuum gas oil (VGO) and the yield of gasoline. However, the simulations showed that longer baffles and a larger number of baffles did not always give a higher yield or higher conversion. Among the simulated configurations, the 5-cm baffles at 5-m spacing gave the highest conversion of VGO, whereas the 10-cm baffles at 1-m spacing resulted in the highest yield of the gasoline. Thus, rational optimization of baffle configurations is required to achieve optimal performance.

Effect of baffle and shroud designs on discharge of a thermal storage tank using an immersed heat exchanger

Heat exchangers immersed in thermal storage tanks are an increasingly popular way to charge and/or discharge energy from the tank. The present experimental study investigates the effects of different baffle and shroud configurations on heat transfer to an immersed copper coil heat exchanger during discharge of a thermal storage tank. The baffle-shrouds create annular regions with the tank wall within which the heat exchanger is located. Negatively buoyant plumes form from the heat exchanger and are directed by the shroud, which surrounds the heat exchanger, into the annular baffle below and through the baffle to the bottom of the tank, while water from the top of the tank is drawn into the top of the shroud to flow over the heat exchanger. Experiments are conducted in 300L unpressurized storage tank filled with initially isothermal water at 60°C. Water flows through the coiled copper tube heat exchanger placed at the top of the tank at a rate of 0.1kg/s and with an inlet temperature of 20°C. Transient heat transfer rate, produced water temperature, fractional energy discharge, temperature distributions in the tank, and NuD–RaD correlations are used to assess how the baffle-shrouds affect tank performance. The three baffle-shroud configurations represent different degrees of fidelity to numerical optimization studies in the literature. However, the simplest design and the one with the least fidelity to those studies—a straight baffle-shroud with a constant width of twice the heat exchanger diameter—performs best by all measures considered. The straight baffle-shroud increases the storage-side convective heat transfer by 27% in the first 90min of discharge relative to a control experiment with no baffle-shroud. The improved heat transfer is attributed primarily to increased velocity over the heat exchanger, though the ∼2°C thermal stratification generated by the baffle-shroud also contributes. The other baffle-shrouds have increasingly narrow baffle regions, which results in lower velocities but slightly higher thermal stratification. The benefit of the slight improvements in thermal stratification is outweighed by the cost of the decreased velocity over the heat exchanger.

Performance and flow field assessment of settling tanksusing experimental and CFD modeling

Settling Basins are one of the most important and popular methods for removal of suspended sediments irrigation and drainage networks or power canals taking off from an alluvial river and wastewater treatment plant. Improving the performance and so increasing sediment removal efficiency of settling basins by an alternative method is necessary. In the present work, the effect of baffle and its angle of attack with the flow (9) on the sediment removal efficiency is investigated by conducting a series of experiments on a straight canal with 8 m length, 0.3 m width and 0.5 m height and 3 m length of basin equipped with an adjustable glass baffle. A numerical analysis has been carried out using ANSYS Fluent 3D software (a general purpose computational fluid dynamics simulation tool) for three Froude numbers from the experiments. The numerical and experimental results were found to match reasonably well.

Investigation of Low-Sidelobe Beampattern Controlling Methods for Acoustic Transmitting Array of Underwater Vehicles

Abstract In underwater unmanned vehicles, complex acoustic transducer arrays are always used to transmitting sound waves to detect and position underwater targets. Two methods of obtaining low-sidelobe transmitting beampatterns for acoustic transmitting arrays of underwater vehicles are investigated. The first method is the boundary element model optimization method which used the boundary element theory together with the optimization method to calculate the driving voltage weighting vector of the array. The second method is the measured receiving array manifold vector optimization method which used the measured receiving array manifold vectors and optimization method to calculate the weighting vector. Both methods can take into account the baffle effect and mutual interactions among elements of complex acoustic arrays. Computer simulation together with experiments are carried out for typical complex arrays. The results agree well and show that the two methods are both able to obtain a lower sidelobe transmitting beampattern than the conventional beamforming method, and the source level for each transmitting beam is maximized in constraint of the maximum driving voltage of array elements being constant. The effect of the second method performs even better than that of the first method, which is more suitable for practical application. The methods are very useful for the improvement of detecting and positioning capability of underwater unmanned vehicles.

Baffle and fixed media effects on coliform removal and bacterial die-off rate coefficient in waste stabilization ponds (a case study in Ahvaz)

Background: The use of waste stabilization ponds is one of the cheapest wastewater treatment processes. This study evaluated the effects of baffles and fixed media on coliform removal in facultative lagoons. Methods: In this study, the settled wastewater from four pond systems of the city of Ahvaz was used as input. Each system was composed of two ponds that were connected to each other serially. Three of them were equipped with two, three, and four baffles. Packages of fixed media were installed in the first baffled pond equal to the number of baffles. During a 12-month sampling period from March 2016 to February 2017, the capability of each system to remove coliform with different detention times was studied. Results: The control system with no baffle and no media reduced the coliform index by an average of 67% in a detention time of 6 to 12 days. Increasing the baffles and fixed media in the ponds improved the coliform removal efficiency; systems with two, three, and four baffles achieved coliform removal in the amounts of 77%, 81%, and 83%, respectively. The coliform die-off coefficients (Kb) were higher in the attached growth systems than in the control system. The coefficients were determined to be 0.21, 0.26, 0.29, and 0.31 d-1 for the second ponds of the control, two-, three-, and four-baffle systems, respectively. Conclusion: This method can be used to upgrade the existing waste stabilization pond and to design new ponds with at least two baffles in the facultative lagoons.

Convective heat transfer of molten salt in the shell-and-tube heat exchanger with segmental baffles

In this paper, a special flow layout with U-shaped tubes applied in the laboratory was designed for testing the heat transfer performances (HTPs) of molten salt in the shell side of a shell-and-tube heat exchanger (STHE). Based on this design, the transitional convective HTPs (6142<Re<9125) of molten salt with higher temperature (209.41–241.49°C) in the STHE with segmental baffles (STHE-SBs) were experimentally studied, and the corresponding heat transfer correlations were fitted. Then the validation of the traditional correlation applied in the molten salt STHE-SBs was conducted. Finally, the comparison of heat transfer enhancement in the molten salt STHE-SBs was discussed. The results show that a good agreement with 2% deviations exists between the fitted correlations and the test data. Meanwhile, the traditional Kern correlation, with a 7.1% maximum deviation compared with the test data, is still appropriate to analyze the HTPs of molten salt STHE-SBs. The effects of segmental baffles on the molten salt heat transfer enhancement in lower flow rate region are better than those in higher flow rate region, and the maximum increment of Nusselt number is 26%.

Structural and petrophysical effects of overthrusting on highly porous sandstones: the Aztec Sandstone in the Buffington window, SE Nevada, USA

Abstract Little is known about the effect of thrusting on lithological and petrophysical properties of reservoir sandstone. Here we use field observations, probe permeability measurements and thin-section analysis along ten transects from the Muddy Mountain thrust contact downwards into the underlying Jurassic Aztec Sandstone to evaluate the nature and extent of petrophysical and microstructural changes caused by the thrusting. The results reveal a decimetre- to metre-thick low-permeable (≤50 mD) and indurated (0–3% porosity) zone immediately beneath the thrust contact in which dominant microscale processes, in decreasing order of importance, are (1) cataclasis with local fault gouge formation; (2) pressure solution; and (3) very limited cementation. From this narrow zone the petrophysical and microstructural effect of the thrusting decreases gradually downwards into a friable, highly porous ( c. 25%) and permeable (≤2 D) sandstone some 50–150 m below the thrust, in which strain is localized into deformation band populations. In general, the petrophysical properties of the sandstone as a result of overthrusting reveal little impact in overall primary reservoir quality below some tens of metres into the footwall, except for the relatively minor baffling effect of deformation bands.

Seismic mitigation performance and optimization design of NPP water tank with internal ring baffles under earthquake loads

The shield building of AP1000 is designed to protect the steel containment vessel of nuclear power plant. Therefore, the safety and integrity must be ensured during the plant life in any conditions such as earthquake. The purpose of this paper is to study the fluid-structure interaction of water in water tank and effects of internal ring baffle on the response of AP1000 shield building under strong ground motions. For this purpose, a fluid-structure interaction algorithm of finite element technique is employed to investigate the seismic response of water tank with internal baffles of different shapes and arrangements under artificial, El-Centro and Kobe earthquakes with peak acceleration of 0.3g. Four optimal designed schemes of different ring baffle types are considered and the influences of various parameters such as vertical baffle height, arrangement locations, baffle height ratio and length of baffle on the dynamical response of shield building are discussed. The numerical results clearly show that the water tank with vertical ring baffle near the bottom of tank can limit the vibration of shield building and can more efficiently dissipate the kinematic energy of the shield building under different earthquake.

Investigation of baffle configuration effect on the performance of exhaust mufflers

Using baffles in exhaust mufflers is known to improve their transmission loss. The baffle cut ratio should affect the muffler performance analogous to a shell-and-tube heat exchanger. To the authors’ knowledge, there is no previous assessment reported in literature of the effects that the baffle cut ratio configuration has on acoustic response and back pressure. This investigation presents a parametric study on the effect of baffle configuration on transmission loss and pressure drop predicted. The effect of (i) the baffle cut ratio and baffle spacing, (ii) the number of baffle holes, and (iii) the hole distribution for their effect on transmission loss was investigated. Results show that decreasing the baffle cut ratio tends to increase the transmission loss at intermediate frequencies by up to 45%. Decreasing the spacing between muffler plates was shown to enhance the muffler transmission loss by 40%. To assess the baffle effect on flow, the OpenFoam CFD libraries were utilized using the thermal baffle approach model. Baffles were found to cause sudden drop in fluid temperature in axial flow direction. The outlet exhaust gases temperature was found to decrease by 15% as the baffle cut ratio changed from 75% to 25%.

Experimental study on vertical baffles of different configurations in suppressing sloshing pressure

The effectiveness of four types of the baffles in suppressing pressure is experimentally investigated under a wide range of forcing frequencies. The dynamic impact pressure variations alongside the central line of the tank wall and the baffle response to different excitation frequencies were measured for tanks without baffles and with immersed bottom-mounted vertical baffles, vertical baffles flushing with free surface, surface-piercing bottom-mounted vertical baffles and perforated vertical baffles, respectively. The maximum impact pressure on the tank wall generally increases with decreasing the distance of the pressure sensor away from the free surface. In the frequency range from 0.4ω1 to 1.4ω1, the vertical baffle flushing with free surface is an more effective tool on reducing impact pressure comparing with the immersed bottom-mounted vertical baffle, especially near the first-mode natural frequency, and effects of the perforated vertical baffle in suppressing sloshing pressure is more significant than that of the surface-piercing bottom-mounted vertical baffle, especially in high forcing frequency region. It is found that the first-mode natural frequency of liquid-tank is altered by the vertical baffles. The experimental results show that changing flow fields and altering natural frequency may effectively suppress the impact pressure on the tank walls.

Experimental and numerical study of air-gap membrane distillation (AGMD): Novel AGMD module for Oxygen-18 stable isotope enrichment

In this article, a novel module is presented to enhance the performance of air gap membrane distillation (AGMD) process. Experimental examinations were performed to modify a conventional AGMD module by presenting a new geometry and analyze the influence of this modification on the performance of the process. Also, three-dimensional (3D) numerical simulation was performed to reveal all aspects of this modification. In numerical study, the momentum, heat and mass transfer equations are solved with turbulent model (k-ε realizable) to observe the flow feature inside the new AGMD geometries. Furthermore, the effect of radial baffles as well as feed flow rate (0.25, 0.50 and 0.75kg/min) are investigated. In order to verify the numerical results, the simulated permeate flux was compared to the experimental data and low discrepancy (less than 6%) was observed. The results also indicate that the mass flux was improved (about 6%) as the rectangular-type module was replaced by the disk-type one. Moreover, our findings show that applying four, six and eight radial baffles to disk type modules significantly enhanced the permeate flux by 10, 13 and 14.7%, respectively. Most importantly, the applicability of the membrane distillation (MD) process for enrichment of 18O water isotope of distilled water was studied using a laboratory operating disk-type AGMD module. This module was employed based on the best-performed geometry obtained from the numerical results. The achieved separation factor was 0.9823 which shows that this approach is a reliable method for isotope separation.

Coupled multimodal fluid-vehicle model for analysis of anti-slosh effectiveness of longitudinal baffles in a partially-filled tank vehicle

An efficient model is formulated for analysis of a coupled fluid slosh-vehicle dynamic system to study the effects of different baffle designs on directional dynamic performance of a partially-filled tank vehicle. A multimodal model of fluid sloshing within a baffled cylindrical tank is initially formulated using potential flow equations and linearized free-surface boundary condition considering maneuver-induced vehicle motions along the lateral, vertical and roll axes. Natural slosh modes/frequencies, hydrodynamic coefficients and Stokes-Joukowski potential associated with the multimodal model are then obtained by solving the eigenvalue problem of free fluid sloshing using a higher order boundary element method. Significant improvement in computational time is achieved by reducing the generalized eigenvalue problem to a standard one involving only the velocity potentials on the half free-surface length using the zoning method. The hydrodynamic force and moment obtained from the multimodal model are subsequently coupled with the TruckSim vehicle dynamic simulation platform through a MATLAB/Simulink model to obtain dynamic responses of a partially-filled tank vehicle with and without baffles under step-turn and double-lane change maneuvers. Two different designs of longitudinal baffles are considered: bottom- and top-mounted baffles. The validity and efficiency of the present boundary element method is demonstrated by comparing the results with those obtained using the boundary element method employing linear elements. The effective mass moment of inertial of the fluid in a clean-bore tank is also obtained as a function of fill ratio and compared with the reported analytical solutions for a half-full tank to further verify the model. The results suggest that directional dynamic responses of partly-filled tank vehicles can be efficiently analyzed using the coupled multimodal slosh-vehicle models with significantly lower computational effort than the methods employing computational fluid dynamic (CFD) fluid slosh models. The results further reveal that top-mounted baffles are most effective in suppressing the fluid slosh force under more likely loading conditions in road tankers.

Effects of Baffles on Sloshing Impact Pressure of a Chamfered Tank

In the following study, the classical Fluid-Structure Interaction (FSI) analysis of sloshing flows is given a new dimension to analyse the stability of the ship by utilization of several mitigating factors. Sloshing near the natural frequency of the tank can result in severe ullage collapse or ballast, whereas in the stable regions sloshing generally leads to cyclic stress and fatigue in thin walled tank structures. The aim is to model the generation and propagation of free surface waves in a tank having bottom baffle arrangements. Important parameters such as filling level and slosh frequency are parametrically varied to assess the impact of each of these parameters on the tank pressure. Further the geometries are studied for four phenomenon that affects the dynamic stability considerably viz. air pockets, flip through, hydraulic jump and roof impact. The comparison of simulated results show significant decline in the value of impact pressure (both maximum and average) in a chamfered tank with the use of baffles at the bottom.

Experimental investigation of the effect of baffles on the efficiency improvement of irrigation sedimentation tank structures

Sedimentation tanks are essential structures to filter the suspended sediments in the inlet flow which are constructed at the inlet of the basins forked from rivers and irrigation canals. The larger the constructed tank, the better the sedimentation process is conducted. However, the construction and dredging costs increase. In this regard, improving the performance and sedimentation efficiency seem necessary by alternative methods. One of these effective methods is using baffle plates. Most of the studies carried out in this field are on the use of these baffles in the primary and secondary sedimentation tanks. Hence, this study is carrier out with the objective of increasing the retention efficiency in the irrigation sedimentation tanks using baffles. To reach this goal, the experiments were carried out in a flume with length 8 meters, width 0.3 meters, and height 0.5 meters, considering a sedimentation tanks with a length of 3 meters, in three different inlet concentration, three flow rates and three Froude numbers. The baffles were mounted at the bottom of the tank and the effects of the angle, height and position in the tanks were investigated. The results showed that on average, employing the baffles increased the sedimentation efficiency 5 to 6% and the highest value was obtained for angle 60 with respect to the flow direction. According to the results of this study, the most favorable height and position of these baffles were obtained to be in 40% of the depth of the flow and 50% of the length of the sedimentation tank, respectively. Also, by increasing the number of baffles, the sedimentation efficiency decreased. Regarding the sedimentation regions in this case, more than 80% of the settled sediments were observed in the middle of the tank measured from the inlet.