Baffle Arrangements Research Articles

A modified resistance model for simulating baffle arrangement impacts on cross-flow microfiltration performance for oily wastewater

As a principal problem in the microfiltration processes, cake formation and concentration polarization phenomena cause permeate flux reduction. In the industrial scale, baffle as a turbulence promoter is an efficient method to decrease the fouling phenomenon. In the current study, eleven baffle arrangements in the feed channel were considered for an oily wastewater emulsion. The baffles with four general configurations of wall baffle, central baffle, baffles installed near the membrane surface, and a combination of them are used. The effects of baffle arrangements on turbulent kinetic energy, turbulent dissipation rate, pressure drop, and shear rate, and oil concentration on the membrane surface are examined under steady-state conditions. A modified model of total resistance is proposed to predict the baffle impacts on the CP and cake layer thicknesses and decrease the computational time. The predicted values are compared against experimental data and the absolute relative error is decreased from 6.54 % to 0.03 % by applying the modified resistance model. As the main results, the baffles installed near the membrane surface are more efficient to separate oil from oil-in-water emulsion but it may be caused some problems at higher processing times and the central baffles are recommended for the industrial applications.

Numerical studies of premixed hydrogen/air flames in a small-scale combustion chamber with varied area blockage ratio

The increasing use of hydrogen as a renewable source of energy underlines the need to be able to assess the safety risks involved in the event of an accidental explosion. This paper presents numerical studies for hydrogen/air propagating flames at an equivalence ratio of 0.7 in a laboratory-scale combustion chamber equipped with turbulence generating baffles and a solid square cross section obstruction. The large eddy simulation (LES) modelling technique is used with an in-house computational fluid dynamics (CFD) model for compressible flows to study the flow turbulence and the flame propagation characteristics. The study is carried out using four different baffle arrangements and two different solid obstructions with area blockage ratios of 0.24 and 0.5. Results for the generated peak overpressure and the timing at which it occurs following ignition are considered as the primary safety factors. The time histories of the flame speed and position relative to the ignition source are validated against published experimental data. Good agreement is obtained between numerical results and experimental data which enables further predictions where measurements are limited in the study of vented hydrogen explosions. It was concluded that adding successive baffles and increasing the area blockage ratio escalates the maximum rate at which pressure rises and raises the generated peak explosion overpressure.

Numerical and experimental study of the heat transfer and hydraulic performance of solar air heaters with different baffle positions

This study presents the results of a numerical and experimental study of the position of the baffles in a solar air heater in order to improve its thermal and hydraulic performance. The numerical study was performed on four cases corresponding to different placements of baffles with Reynolds numbers ranging from 2370 to 8340. The experimental model of the solar air heater was designed, manufactured and used for the validation of the numerical model. The new baffle placements show that effective thermo-hydraulic performance is not just a function of the shape or changes in the geometric parameters of the baffles. The correct placement of baffles dramatically improves the thermo-hydraulic performance of solar air heaters. The effect of baffle positions on local convective heat transfer coefficients has been discussed. The optimum thermo-hydraulic performance factor is achieved in the case where the baffles are located in the first part of air channel which occupies 50% of the solar air heater.

Enhancement of the cooling of shear-thinning fluids in channel heat exchangers by using the V-baffling technique

The present work is a study of the performance of a channel heat exchanger equipped with V-baffles. The study is carried out numerically by using a multidimensional CFD model (the Software ANSYS CFX v.18). Among the different techniques available to improve the efficiency of heat exchangers, we choose in this work the technique of vortex generators (baffles). The simulated fluid is a complex shear-thinning solution and the flow regime is laminar. The influence of some parameters on the efficiency of such heat exchanger has been verified, namely the flow rate (Reynolds number), the orientation of baffles and their arrangements. Two orientations of baffles are selected: +V and −V, corresponding to the counter direction of flow and the same direction of flow, respectively. Also, the staggered and aligned arrangements of +V baffles are studied. The predicted results revealed that +V baffles inserted in the staggered arrangement may give a considerable superiority in enhanced heat transfer ratio, compared to the (−V) baffles’ insertion and the aligned arrangement. Values of the thermal performance factor for the +V aligned arrangement, −V aligned arrangement and +V staggered arrangement of baffles are: 1.44, 1.32 and 1.52, respectively.

Effect of flow rates on segmental baffle shell and tube heat exchanger using CuO-W nanofluids

Purpose Nanofluid exhibits higher density, higher viscosity, higher thermal conductivity and reduced specific heat capacity along with improved heat transfer characteristics. It is comparatively better than conventional fluids in terms of thermo-physical properties. This paper aims to investigate experimentally the overall performance of the shell and tube heat exchanger operated under two different configurations – without baffles (STHX_1) and with baffles (STHX_2) using 0.01 Vol.% and 0.02 Vol.% of CuO-W nanofluid. Design/methodology/approach Two different configurations, one without baffles (STHX_1) and other with single segmental baffles (STHX_2), are chosen with all other dimensional details of shell and tube remaining same. Water is used as base fluid. CuO nanoparticle is chosen, as its thermal conductivity is higher compared to other metal oxides. A comparative study on the thermal performance of these shell and tube heat exchangers are performed by considering different Vol.% concentrations of CuO-W nanofluid and the outcome are compared with the base fluid (i.e., water). The influence of varying the mass flow rate of the tube side fluid by keeping shell side fluid mass flow rate as constant and vice versa on the thermal performance of shell and tube heat exchanger are studied. Findings The modified shell and tube heat exchanger with baffles (STHX_2) give an improved performance. The heat transfer coefficient improved by about 11.28 and 7.54 per cent for 0.02 and 0.01 Vol.% of CuO-W nanofluid compared to water. Overall heat transfer coefficient for STHX_2 enhanced between 118.26% to 123.06% in comparison with base fluid for 0.02 Vol.% of CuO-W nanofluid whereas, it improved between 79.20% to 87.51% for 0.01 Vol.% of CuO-W nanofluid. Similarly, the actual heat transfer enhanced between 71.79% to 77.77% and between 48.71% to 55.55% for 0.02 and 0.01 Vol.% of CuO-W nanofluid, respectively. Moreover, mass flow rates of the working fluids significantly influence the performance of the shell and tube heat exchanger. Originality/value Two cases are considered here. first, by varying the shell side fluid mass flow rate and keeping the tube side fluid mass flow rate as constant. Later, tube side fluid mass flow rates are varied and shell side fluid mass flow rate is kept constant. It is found that in Case 2, for both 0.01 and 0.02 Vol.% of CuO-W nanofluid, highest performance is obtained for 150 kg/h of shell side and tube side fluid flows involving STHX_2. Finally, the modified shell and tube heat exchanger with baffle arrangement gives the best performance by using 0.02 Vol.% of CuO-W nanofluid.

Improving the efficiency of an exhaust thermoelectric generator based on changes in the baffle distribution of the heat exchanger

A significant amount of the heat is lost in the vehicle exhaust and simply transferred to the environment. Using a thermoelectric generator (TEG), it is becoming possible to convert this heat potential into the electrical energy. In this study, nine types of the heat exchangers in three different groups, namely A, B, and C are modeled in three dimensions and studied using computational fluid dynamics (CFD) analysis with various baffle arrangements to obtain electrical energy from the vehicle exhaust. The modeling of the group A is focused on the effect of the angle and thickness of the baffles at the inlet of the heat exchanger. In the group B, the distances between the baffles and their heights are changed, and group C is focused to model larger baffles with different arrangements. The results show that, the pressure drop is in the permissible range in all the models, and the gas flow velocity in group A is almost similar to what studied in other models; however, the power produced in it is at least 7.25% higher than other models. The best model for the highest generated power is also recommended and discussed. It is also shown that implementation of a deflector will lead to a non-uniform and unidirectional distribution of temperature. The results also reveal that under identical conditions in the middle section of the heat exchanger, reducing the height of the baffles from 8.46 mm to 2.30 mm will result 10.88% decrease in the output power. Furthermore, increasing the distance between the baffles from 5.2 mm to 16.8 mm will cause 3.91% increase in the output power.

Heat transfer and pressure drop evaluation of different triangular baffle placement angles in cross-corrugated triangular channels

Plate heat exchangers have a widespread usage and the simplest parallel plate channel structures. Cross-corrugated ducts are basic channel geometries used in the plate heat exchangers. In this study, the increasing of heat transfer from the cross-corrugated triangular ducts by inserting triangular baffles with different placement angles into the channel upper side and pressure drop have been numerically investigated. Numerical calculations have been carried out to solve Navier-Stokes and energy equations by employing k-? turbulence model as 3-D and steady with ANSYS-FLUENT program. While inlet temperature of the air used as working fluid is 293 K, constant surface temperature values of the the lower corrugated channel walls are 373 K. The height of the baffle and apex angle of the corrugated duct have been taken constant as 0.5 H and 60?, respectively. Investigated Reynolds number range is 1000-6000 while the baffle placement angles are 30?, 45?, 60?, and 90?. Numerical results of this study are within 3.53% deviation with experimental study existed in literature. The obtained results have been presented as mean Nusselt number temperature and pressure variations of the fluid for each baffle angle. The temperature and velocity vector contour distributions have been also assessed for different Reynolds numbers and baffle angles. The value of the Num for the corrugated channel with 60? baffle angle is 8.2% higher than that of the 90? for the Re = 4000. Besides, for Re = 1000 the value of the pressure drop is 39% lower in the channel with 60? baffle angle than that of 90?.

Thermohydraulic characteristics of inline and staggered angular cut baffle inserts in the turbulent flow regime

In the present work, heat transfer and pressure drop characteristics in flow through a tube with inline and staggered baffles having angular cut at the edge are reported for various operating conditions. An experimental test rig is designed and developed to investigate heat transfer and pressure drop behavior for different conditions. Effects of different geometrical parameters, i.e., pitch ratios, baffle arrangement and cutting angle of baffles on heat transfer rate and pressure drop characteristics, have been investigated for turbulent flow regime. Reynolds number ranging from 10,000 to 52,000 has been considered in the present study. The maximum heat transfer rate has been observed for staggered arrangement with pitch ratio of 0.1 and cutting angle of 60°, while minimum heat transfer rate has been observed for inline arrangement with pitch ratio of 0.2 and cutting angle of 30°. Empirical correlations for Nusselt number and friction factor have been developed as a function of geometrical and flow parameters. The deviations between experimental and predicted values of Nusselt number and friction factor for staggered arrangements have been observed as ± 10%, ± 4%, respectively, whereas for inline arrangement the deviation has been observed as ± 12%, ± 5%, respectively. Results from empirical correlations are well agreed with the experimental data.

Predicting and analyzing the performance of biomass-burning natural draft rocket cookstoves using computational fluid dynamics

Nearly three billion people in the world today rely on biomass for their cooking needs. Indoor cooking using biomass has been identified as a major cause of respiratory illnesses, resulting in four million premature deaths every year. Improved biomass cookstoves may help mitigate this challenge. This paper presents a two-dimensional axisymmetric steady-state computational fluid dynamics (CFD) model of a biomass burning, natural draft rocket cookstove. The CFD model includes coupled sub-models representing combustion, turbulence, and heat transfer. The model is validated against experimental data and used to predict temperatures and flow inside the cookstove, including the airflow rate through the cookstove and heat transfer to the cookpot. We find that the excess air is typically many times stoichiometric air during standard operating conditions and is sensitive to flow field obstructions. We analyze the effects of geometric and operational features such as the pot support height, secondary air entrainment, cone-deck shape, and baffle placement within the cookstove on the flow, airflow rate, mixing, and stove thermal efficiency. The model shows that secondary air entrainment, though ineffective by itself, increases turbulent mixing when used in conjunction with a central baffle but reduces thermal efficiencies due to enhanced heat transfer to the walls. We find that a lower pot support height decreases the airflow rate and increases thermal efficiency. We model thirty-six cone-deck configurations and find that the cone-deck shape primarily affects the airflow rate through the stove, with more constricted designs leading to higher thermal efficiencies.

Experimental study of a solar air heater by adding an arrangement of transverse rectangular baffles perpendicular to the air stream

ABSTRACTThe aim study in the solar air collector is a focus on the matter of the deficiency of the thermal transfer between the fluid and the absorber plate, so we built a thermal solar flat plate collector and made some adjustments. The collector was built in the hall of Department of Mechanical Engineering based in the University of Biskra, by considering to minimize the thermal losses to the minimum and increasing the difference between the inlet and the outlet temperatures (thermal efficiency) by adding a rectangular baffles perpendicular to the air stream. The experiment was divided into different modes. Each mode has its own specific number and placement of baffles. This article represents the results that were taken from the experimental study, which shows the increase in the thermal efficiency by a significant value. We also present the effects of other variations on the thermal efficiency itself. It has also been found that thermal efficiency with median and all placement transversal baffle of solar air heater is greater than another mode, using same air flow rate and number of baffles. Finally, the pressure drop associated with increasing number of baffles and air flow rate was deliberated.

An isogeometric boundary element method for liquid sloshing in the horizontal eccentric annular tanks with multiple porous baffles

Boundary element method (BEM) coupled with the isogeometric boundary based on Non-Uniform Rational B-Splines (NURBS), which is termed IGABEM, is a new numerical method and has attracted wide attention in recent years. In this paper, IGABEM is first applied to the liquid sloshing problem in the horizontal rectangular, circular or elliptical annular tanks with multiple porous baffles, assuming incompressible, irrotational and inviscid flows. As a key improvement compared with the conventional polynomial shape function in BEM, the IGABEM for the analysis of liquid sloshing can exactly represent the geometry no matter how coarse discretize the studied boundary, which then produces no geometrical errors. A zoning method is carried out to study arrangement of the multiple porous baffles in the tanks. Neighboring zones is joined together by the boundary conditions of the porous baffles and virtual interface which correlate the flux and velocity potential. By discretizing boundaries of each zone using the isogeometric function, the governing integral equation on the boundary by using BEM can be formulated into the dynamic equation in frequency domain. Three configurations of baffles are taken into account such as the top-mounted baffles, bottom-mounted baffles and annular baffles. The results obtained by the proposed method are verified by comparing with the reported solutions and very good agreement is obtained. The effects of tank's geometry, liquid filling level and the baffle's parameters with various lengths, submergence depths, number of baffles, and porosities on the natural sloshing frequency, wave surface elevation, sloshing force and velocity field are investigated and several conclusions are achieved.

Experimental and numerical investigation on shell-and-tube exhaust gas recirculation cooler with different tube bundles

The heat transfer characteristics of shell-and-tube exhaust gas recirculation (EGR) coolers with different tube bundles were studied by experiment and numerical simulation. The overall heat transfer coefficient and shell-side pressure drop were determined. The influences of tube spacing, baffle form, baffle arrangement and number on the overall heat transfer coefficient and shell-side pressure drop were investigated. The maximum differences between the numerical and experimental results are approximately 4.1% for overall heat transfer coefficient and 3.3% for shell-side pressure drop, respectively. The results indicate that the overall heat transfer coefficient of EGR cooler with wave fin arrays internally finned tubes is 1.3~1.7 times than that of EGR cooler with longitudinal plate-rectangle internally finned tubes. And the comprehensive heat performance is more reasonable when tube spacing and baffle number are equal to 12 mm and 9, respectively. It is confirmed that the trisection ellipse helical baffle is superior to the segmental baffle, but the influence of improving overall thermal performance by setting baffles is limited for small EGR cooler.

3D optimization of baffle arrangement in a multi-phase nanofluid natural convection based on numerical simulation

PurposeThe purpose of this study is investigating the effect of using multi-phase nanofluids, Rayleigh number and baffle arrangement simultaneously on the heat transfer rate and Predict the optimal arrangement type of baffles in the differentiation of Rayleigh number in a 3D enclosure.Design/methodology/approachSimulations were performed on the base of the L25 Taguchi orthogonal array, and each test was conducted under different height and baffle arrangement. The multi-phase thermal lattice Boltzmann based on the D3Q19 method was used for modeling fluid flow and temperature fields.FindingsStreamlines, isotherms, nanofluid volume fraction distribution and Nusselt number along the wall surface for 104 < Ra < 108 have been demonstrated. Signal-to-noise ratios have been analyzed to predict optimal conditions of maximize and minimize the heat transfer rate. The results show that by choosing the appropriate height and arrangement of the baffles, the average Nusselt number can be changed by more than 57 per cent.Originality/valueThe value of this paper is surveying three-dimensional and two-phase simulation for nanofluid. Also using the Taguchi method for Predicting the optimal arrangement type of baffles in a multi-part enclosure. Finally statistical analysis of the results by using of two maximum and minimum target Function heat transfer rates.

Sloshing dynamics and performance of porous baffle arrangements in a barge carrying liquid tank

An experimental investigation is conducted to explore the effectiveness of porous baffles placed at l/3 and 2l/3 in the sloshing tank. A tank aspect ratio, hs/l of 0.488 which corresponds to 75% filled condition is considered. The sloshing tank is kept inside the freely floating barge and subjected to regular beam sea waves. A wave height of 0.1 m and excitation frequencies ranging from 0.45 Hz to 1.54 Hz is adopted. Baffles with three different porosities of 15%, 20.2% and 25.2% are used. The effectiveness of baffles placed at l/3 and 2l/3 is explored on comparison with the performance of single porous baffle kept at l/2 and a solid submerged baffle place at l/2. Sloshing dynamics for the baffles placed at l/3 and 2l/3 and barge responses are also discussed.

Implication of fluid rheology on the hydrothermal and entropy generation characteristics for mixed convective flow in a backward facing step channel with baffle

The present study numerically investigates a two-dimensional, steady, laminar, incompressible and mixed convective flow of non-Newtonian fluid through a backward facing step channel with different baffle configurations. The power-law model is used to capture the confluence of fluid rheology and buoyancy for varying step to baffle distance, varying number of baffles and different arrangement (inline and staggered) of baffles. Different values of power-law index viz. n = 0.5, 0.8, 1, 1.2 and 1.5 are considered to encompass the shear-thinning (n < 1), shear-thickening (n > 1) as well as Newtonian fluids (n = 1) as a special case. The Reynolds number is fixed equal to 100 whereas the Richardson number has been varied within the range of 0.1–1 in the present investigation. The results obtained from the present investigation reveal the implications of power-law index, Richardson number and baffle configuration on the reattachment length, Nusselt number, pressure drop and entropy generation. The results show that the length of the recirculation zones formed in the backward facing step channel increases with increase in Richardson number and decreases with increase in power-law index. It is also found that the variation of heat transfer rate, pressure drop and entropy generation characteristics for varying step to baffle distance, different number of baffles and different arrangement and number of pairs of baffle is dictated by the interplay of power-law index and Richardson number. The findings of this study bear utility towards designing efficient thermodynamic system that can deliver maximum heat transfer with minimum irreversibility.

Analysis of the Impact of the Baffle Placement in the Supersonic Flow in the Differentially Pumped Chamber

The thesis follows to the work of G.D. Danilatos occupy Differential Pumping System with fast stopper focusing on dew design for environmental scanning electron microscope. Thesis concern divider located in the chamber differential pumping and its influence on the nature of the flow. Simulation of individual variants was evaluated using the program Ansys Fluent, which calculates with the method final volumes as opposed to calculations performed by G. D. Danilatos which uses the statistical method Monte Carlo.

Locally resonant stop band acoustic metamaterial muffler with tuned resonance frequency range

Exhaust noise and pollution are the main environmental drawbacks of internal combustion engines. Although humans may seem to have become accustomed to noise, but they are continuously exposed to its risks. This paper aims to investigate exhaust noise and provide an improved design for the construction of muffler internal baffles. In this regard, locally resonant acoustic metamaterial baffles (AMB) were shown to be promising in the sense of transmission loss at desired high, medium and low-frequency domains. Hence, in terms of acoustic performance, a specific frequency range was targeted to be influenced by the changes made in the design of AMB resonators. To better characterize the AMBs, the arrangement and number of baffles were studied using resonators with different natural frequencies. Results were compared to those related to an empty cylindrical muffler model and previous studies. Findings indicate that the AMBs clearly enhance the muffler transmission loss to values up to 85 dB and that not only resonator dimensions, but also spacing of the baffles play an important role in the improvement of the transmission loss. Finally, to evaluate the real operational performance of the muffler, important factors such as flow and pressure drop are also considered and highly reasonable results are obtained.

Numerical Modelling of Fish Passage with Turning Pools

Abstract An assessment of operating conditions in a baffled fish passage with pool dimensions of 2.2 × 3.0 m, and 180° horizontally turning pools, was carried out using numerical computations and a site survey of water flow velocity distribution. Velocity was measured with a PMS electromagnetic flowmeter and a hydrometric current meter in representative cross-sections of the fish passage in the pool centres and in the baffle barrier cross-section area. Numerical computations were also performed for two alternative baffle locations in the fishway. One reflected the actual conditions, and the other was an alternative arrangement designed to improve hydraulic conditions for fish migration. The numerical model used the Large Eddy Simulation (LES) method, which makes it possible to detect large vortexes. The study pays close attention to the velocity field analysis as well as the distribution and sizes of vortexes in the turning pool of the culvert. The results of numerical computations and the site survey show high consistency, and the proposed baffle placement modification significantly improves flow conditions, especially in the entry section of the passage.

Hydrothermal performance and entropy generation analysis for mixed convective flows over a backward facing step channel with baffle

In this work, we numerically investigate the thermo-hydraulic characteristics and entropy generation for mixed convective flow through a backward facing step channel with baffle. The effect of baffle geometry is studied by considering three different shapes for the baffle viz. square, triangular and elliptical and two different baffle sizes viz. hb × wb = 1 × 1 and hb × wb = 2 × 2 designated as B1 and B2 configuration respectively. Parametric studies are also carried out to analyse the effects of baffle to step obstruction distance, number of baffles and arrangement of baffles in inline and staggered order on the fluid flow, heat transfer and entropy generation characteristics. Local and average Nusselt number, pressure drop and entropy generation are computed for all the configurations at a fixed Reynolds number Re = 100 and for a range of Richardson number Ri = 0.1–1. Our study reveals that the reattachment length decreases with the addition of the baffle inside the channel and the length is inversely proportional to the size of the baffle. Peaks of local Nusselt number are observed in the region near the baffle and the magnitude of these peaks are dependent on the baffle shape and size. It is observed that local entropy generation is minimum within the re-circulation zone while the same is maximum at the reattachment point. The larger the distance of baffle from step, the smaller is the total irreversibility associated with it and its magnitude is the least in case of elliptical baffle for both the configurations. For any baffle shape having B1 configuration, the average Nusselt number, the average pressure drop and the total entropy generation are minimum for two baffles both mounted on the top wall, while these parameters predict an increasing trend with increasing number of baffles for B2 configuration. In case of pair of baffles mounted both on the top and bottom walls, inline arrangement of baffles always incur higher heat transfer performance, pressure drop penalty and entropy generation as compared to staggered arrangement. For all the number of pairs of baffles in staggered arrangement, elliptical baffles always provide the highest heat transfer performance, least pressure drop penalty and least entropy generation among all the baffle geometries and as such in staggered arrangement, elliptical baffles in backward facing step channel is an optimum design choice from the perspective of both the thermo-hydraulic performance and entropy generation.

Dynamic response of AP1000 water tank with internal ring baffles under earthquake loads

AP1000 is a standard design developed by Westinghouse for an advanced generation III+ nuclear power plant (NPP) utilizing passive features. Water storage tank of AP1000 plays an important role in cooling down the temperature of the inside of the NPP. However, the water sloshing and fluid-structure interaction effects of AP1000 water storage tank have an important influence on the dynamic response and safety of the nuclear power plant under strong ground motions. In this study, a fluid-structure interaction algorithm of finite element technique is employed to investigate the seismic response of water tank with internal baffles. Four schemes of ring baffle types are considered and the effects of various parameters, such as vertical baffle height, arrangements, and length of baffle on the dynamical response of shield building are investigated. It is indicated that the case 1 with vertical ring baffle near the bottom of tank is the best scheme for reducing dynamic response of shield building in AP1000.