Baffle Height Research Articles

Experimental studies and 3D simulations for the investigation of thermal performances of a solar air heater with different spiral-shaped baffles heights

A new design of Solar Air Heater (SAH) with spiral flow path is studied experimentally and numerically. The spiral-shaped SAH performance is studied at various mass flow rates, inlet temperatures, radiation intensity and baffle heights. Similarly, a CFD model is developed using “ANSYS Fluent” software to study the fluid flow and heat transfer in the SAH. Mesh independence is performed in order to choose the appropriate mesh. The discrete ordinate (DO) radiation model and the k-ω Shear Stress Transport (SST) turbulence model are used to study the radiative heat transfer and the turbulent flow, respectively in the SAH. Effects of different baffle heights (42 mm,50 mm,70 mm,90 mm, 110 mm and 130 mm) for different mass flow rates (input velocities:5 m/s,10 m/s,15 m/s, 20 m/s and 25 m/s) are numerically investigated. Local flow characteristics are presented and discussed. The results show a good agreement between the numerical model and the experimental data with an average error of 3.6%. The maximum outlet air temperature of the SAH during the test days reached 77.7 °C with input velocity of 5 m/s. The maximum thermal efficiency is founded for geometries having 110 mm and 130 mm baffle-heights ranges between 40% and 59% for an airflow of 0.0075 kg/s and 0.038 kg/s, respectively. The geometry having a 110 mm baffle-heights shows the optimum thermal performance of 13% higher than standard geometry (50 mm baffle height).

Study of relative energy dissipation of trapezoidal and arced piano key weirs equipped with baffles

Abstract Energy dissipation is one of the important issues in piano key weirs (PKWs). Excessive energy at the weir's toe can cause scouring. In the previous studies, energy dissipation of the arced piano key weirs (APKWs) has not been investigated. In this experimental study, the effect of weir height as well as the height and arrangement of the baffles located on the outlet key slope on the amount of dissipated energy were examined in trapezoidal piano key weirs (TPKWs) and APKWs. Experiments were performed on models with two weir height to the width of a cycle ratios equal to 0.9 and 1.2, three baffle height to the width of a cycle ratios equal to 0.06, 0.12 and 0.18 and two A and B-arrangements. The results showed that with the increase in discharge, the amount of relative energy dissipation decreases. The amount of relative energy dissipation is higher in weirs with higher height and also in weirs with larger baffles. Also, the arrangements of the baffles located on the outlet key slope has a significant effect on the amount of dissipated energy.

Heat transfer augmentation in solar heat exchanger duct with louver-punched V-baffles

A vortex generator's ability to create secondary flow and accelerate rapid fluid mixing allows it to effectively improve thermal performance in a solar heat exchanger duct. A newly created louver-punched V-baffle (LPVB) vortex generator was tested experimentally in the current study and the flow and thermal patterns were also investigated using a three-dimensional CFD simulation. The Realizable k–ε turbulence model was utilized in the simulation and the predictions were verified using experimental data and correlations. By directing the impinging air onto the duct's heated surface, the square louver on the baffle served the primary function of reducing pressure drag. Air was used as the test fluid, flowing at Reynolds numbers (Re) from 5300 to 23,000 into the constant heat-fluxed duct. On the heated wall that was set up by letting the V-apex direct upstream, the LPVBs with a 45° attack angle (α) were repeatedly positioned. There were two aspects to the current investigation. First, the optimal relative baffle pitches (PR) and louver angles (β) conditions were determined by looking at the LPVB characteristics, which included four β and three PR at a fixed relative louver size (LR = 0.5) and baffle height (BR = 0.4). Second, three relative louver sizes (LR = 0.3–0.9) were investigated at the optimal PR and β. According to the results, the solid-baffle friction loss is significantly reduced by the LPVB with β > 0° while the heat transfer is slightly lower. In the first part, the LPVB with PR = 1.5, β = 45° has the optimal performance while in the second part, the one with LR = 0.9 yields the greatest performance. A numerical flow model was computed to understand the flow and thermal patterns. The findings were verified using the available measurements, and there is close agreement between the experimental and numerical results.

Numerical Study on the Effect of an Improved Three-Partition Baffle Flow Field on Proton Exchange Membrane Fuel Cell Performance.

The proton exchange membrane fuel cell (PEMFC) is a type of efficient and environmentally friendly battery. The structure of its bipolar plate directly affects reactant transport and liquid water removal and thereby affects the fuel cell performance. An improved three-partition trapezoidal baffle flow field based on the conventional trapezoidal baffle flow field design is proposed in this paper. A three-dimensional multiphase PEMFC model was established by considering the Forchheimer inertial effect. The mass-transfer characteristics and fuel cell performance of the improved three-partition baffle flow field were compared with those of the conventional parallel flow field and ordinary trapezoidal baffle flow field. It was observed that both improved three-partition baffle flow field and ordinary trapezoidal baffle flow field reduced the flow velocity near the baffle to enhance the inertial effect and mass transfer. In addition, improving the three-partition baffle flow field by further optimizing the baffle heights in different regions of the ordinary trapezoidal baffle flow field improved the transverse flow transmission and the inertial effect near the three-partition baffles. The water removal capability of the porous electrode and the PEMFC performance also improved. The net power of the improved three-partition baffle flow field increased by 4.8% compared with that of the conventional parallel flow field. This study provides an effective reference for the study of the PEMFC bipolar plate structure.

Hollow trapezoidal baffles in a rectangular channel: Thermal/hydraulic assessment with ANN numerical approach

In this study, thermal/hydraulic performance (THP) of a heated bottom surface channel, on which hollow straight, elliptic, and wavy top surface trapezoidal baffles are attached, have been investigated. Artificial neural network modeling (ANN) and 3D ANSYS numerical valuations are presented and validated using experimental data obtained by Sahin et al. (2019). Six parameters are studied: baffle height (H), baffle width (S), baffle length (L), corner angle (α), inclination angle (β), and Reynolds number (Re). This study is carried for both aligned and staggered baffles configuration. Air is considered to be the working fluid at a range of Reynolds number (5 × 103 ≤ Re ≤ 2.3 × 104). Backpropagation technique used to determine the optimal ANN size with the Bayesian regularization algorithm. Results show that the most effective parameters on THP are Re, α, and H. Based on the thermal hydraulic efficiency values, the optimum condition is obtained at α= 16°, β = 0°, and baffle dimensions of H = 20 mm, L = 25 mm, S = 26 mm. The average value of thermal enhancement factor (TEF) shows that the staggered arrangement is superior to aligned one for all baffle shapes at the optimum condition. The largest TEF is 1.2 which is captured for the case of the wavy top surface trapezoidal baffles in staggered arrangement at Re = 5000.

Entropy generation and thermal performance of tubular heat exchanger fitted with louvered corner-curved V-baffles

The current article deals with an experimental study on entropy generation analysis and thermohydraulic performance of a uniform heat-flux tube equipped with louvered corner-curved baffle tape (LCBT). Air was drawn into the inserted tube for the Reynolds number (Re) between 4760 and 29,300. The V-shaped LCBT arranged by V-tip in downstream direction was introduced with three baffle pitch ratios (PR = 1–2) and six louver angles (θ = 0–90°) for a fixed attack angle (α) of 30° and baffle height ratio (BR = 0.25). The impacts of investigated parameters on the thermal enhancement factor (TEF), Nusselt number (Nu), friction factor (f), and total entropy generation (S˙gen′) were examined. The measurements showed that the LCBT with the smallest values of PR = 1, θ = 0° give the largest Nu and f at about 4.4 and 19.2 times above the plain tube values, respectively. However, the greatest TEF around 2.23 was seen for employing the LCBT at PR = 1, θ = 45°. The entropy analysis also showed that the S˙gen′ is found to decline with the increment of PR and θ, whereas the minimal S˙gen′is at PR = 1, θ = 0° for lower Re but at PR = 1, θ = 45° for higher Re. Furthermore, the Nu and f empirical correlations for employing LCBTs were also proposed.

Impact behaviour of dry granular flow against baffle structure: coupled effect of Froude and particle characteristics

The baffle design resisting dry granular flow is still impeded by the effect of the particle size distribution coupled with the influence of Froude characteristics on baffle performance – for example, the deceleration process and run-up process. Based on discrete-element method simulation, this study investigated the baffle deceleration and granular flow run-up. Baffle deceleration is controlled by the change of particle contact behaviour behind the baffle slits and is more sensitive to the particle size than the Froude characteristics of granular flow. Although the granular flow run-up height is also affected by the debris–slit interaction, it is mainly dominated by the flow climbing along the baffle, which is more sensitive to the Froude characteristics and stress-transfer mechanism. Bidisperse granular flow has more complex interaction with the baffle compared with monodisperse flow. The effect of material inhomogeneity on baffle performance depends on the particle content. For baffle design, the first array can be considered as a reference. The estimation of the baffle deceleration potential and height with consideration to unsteady dynamics and material inhomogeneity is also presented in this paper.

SPH-Based Numerical Study on the Influence of Baffle Height and Inclination on the Interaction between Granular Flows and Baffles

Arrays of baffles are widely used to prevent and mitigate granular flows (e.g., debris flows and landslides) in mountainous areas. A thorough understanding of the decelerating effect and the impact force of the baffle arrays is essential for engineering design and hazard mitigation. However, the interaction mechanism of granular flows and baffles is still not fully understood. In this work, numerical simulations based on the smoothed particle hydrodynamics (SPH) method are performed to investigate the influence of baffle height and inclination on the interaction between granular flows and baffles. It is found that the SPH model can well capture the flow kinematics of granular materials through the baffles and can obtain the impact force acting on the baffle structures. The results indicate that the performance of baffles is affected by the overflow of granular flows and increasing baffle height can effectively improve the deceleration effect on granular flows. However, the impact force analysis shows that the strength of higher baffle structures also needs to be increased in engineering design. In addition, the peak impact force is found to be closely related to the Froude number Fr.

Experimental and numerical investigation of natural convection for a fully closed cabinet subject to chimneys

This study focuses on the improvement of the natural convection heat dissipation performance of a fully closed cabinet. Both experiments and simulations are performed for eight different cases to examine the effect of the heat sink with chimney effect, baffle, ceiling and ceiling angle with different perforation. A heat sink is introduced to form dual chimneys to separate/facilitate the airflow circulation in the interior and exterior of the cabinet. The heat generation is 90 Watts and the exterior ambiance is around 25 °C. The chimney effect of the heat sink with baffle improved the airflow circulation by reducing 11–14% of the thermal resistance (TR) than the reference case. TR was found to increase with the increase in baffle height and decrease with the increase of perforation and ceiling angle, respectively. The overall analysis recommends the optimized parameters namely, baffle length 175 mm, 20 mm opening height under the baffle, length of ceiling plate to be 75 mm with 20% perforation, ceiling height 75 mm with 20% perforation and 27-degree ceiling angle. The optimized design reduced the TR by 17.9% than the base case standardizing the natural convection potential that can enhance the airflow and heat transfer.

Flow field structure design modification with helical baffle for proton exchange membrane fuel cell

To effectively improve the fuel cell (FC) mass transport capacity, a new flow field (FF) design with helical baffle at the cathode is proposed, which facilitates gas flow and mass transfer in both through- and in-plane directions. To fully understand the influence of various design parameters on the FC performance, a series of studies were carried out with a semicircular baffle as an example. The effect of the baffle structure on the complex heat and mass transport process is studied in detail to obtain the optimal baffle structure parameters. To simulate the complete transport process, a three-dimensional, multiphase, non-isothermal steady-state model was developed, embedding the anisotropic transport properties caused by the porous layer structures and the heterogeneous model of the actual agglomerate structure of the catalyst layer in the model. The results show that the helical baffles induce cross flow under the ribs while inducing forced convection, enhancing the oxygen supply in both directions. The FF structure with baffle height and pitch of 0.4 mm and 1.0 mm respectively has the maximum net power density. Taking the relative humidity = 50 % and 100 % as an example, the net power density is increased by 11.42 % and 5.72 % respectively compared with the original FF.

Experimental Study on the Impact Dynamics of Cylindrical Baffles with a Rigid Barrier against Debris Flows

The use of baffle arrays behind a rigid barrier is an effective method to reduce impact force by dissipating flow energy with filtering boulders from debris flows. To prevent structural damage of the rigid barrier, appropriate configurations of the baffle arrays are needed; however, design guidelines for the geometric construction of baffle arrays have not yet been proposed. One of the major challenges in designing multiple structures (baffles and a rigid barrier, etc.) is to set up a framework for a safe and economical design. The flow–structure interaction and impact force of debris flows on a rigid barrier are affected by the configuration of baffles installed behind the rigid barrier. In this study, to evaluate the flow behavior and the dynamic impact force on the terminal barrier after the flow has passed through the baffle arrays, we conducted a series of small-scale flume tests under various baffle heights and a number of rows. The test results revealed that the installation of baffles reduced the run-up height and the impact force on the terminal rigid barrier. The flow impedance induced by baffles had a significant influence on the dissipation of the kinetic energy of debris flows. Moreover, additional baffle rows produced a greater reduction in the run-up and impact force by decreasing debris flow and boulder mobility.

INSIGHT INTO AN EFFICIENT MICROMIXER WITH STAGGER ABREAST BAFFLES

Passive micromixers utilize no external energy input. It mainly depends on the structure change of microchannel to produce chaotic convection effect, which increases the contact surface and contact time between the fluid. The mixing efficiency of stagger non-abreast baffles (SNB) micromixer and stagger abreast baffles (SAB) micromixer is compared at five kinds of Reynolds (Res). It may affect the mixing efficiency including the height ([Formula: see text]) and number ([Formula: see text]) of baffles, the distance between two adjacent baffles, non-abreast baffles, and abreast baffles. As the [Formula: see text] of the baffles changes, it contributes to enhance the chaotic convection of the micromixer. When Re [Formula: see text], the worst mixing efficiency of the most efficient seven SABs ([Formula: see text], [Formula: see text] mm, [Formula: see text] mm, [Formula: see text]) micromixer reaches an astonishing 98%. The concentration change along the microchannel is studied in this paper. At low Re, SAB makes fluid contact zigzag in microchannel and enhances molecular diffusion. At high Re, SAB causes chaotic convection in the microchannel and completes the mixing quickly.

Influence of a vertical baffle on suppressing sway motion response of a tank coupled with sloshing actions in waves

The present work is a direct extension of our previous work in Jiang and Bai (2020) where the sway motion response of a box section coupled with an internal sloshing flow was studied. In the present work, vertical baffles are equipped at the bottom of the internal tank, and the influence of the vertical baffles on suppressing the internal sloshing flow as well as the sway response of the system in waves is assessed. The IRF method and the CFD simulation are applied to consider the internal and external fluid flows, respectively. Numerical simulations show that the increased vertical baffle height can generate a more significant effect on suppressing the coupled sloshing action, where the sway motion amplitudes of the baffled sloshing tank tend to the empty tank results. Whether the internal sloshing flow breaks or not seems to play an important role in affecting the sway response of the tank. The vertical baffle can block the sloshing flow and generate a significant effect on the sway motion response when the sloshing flow is of the breaking pattern. For a specific relative vertical baffle height, the shallow filling depth or the large incident wave amplitude is more prone to generate the breaking sloshing flow, and hence better suppressing action can be obtained. As for the non-breaking sloshing flow motion, the vertical baffle is hard to generate the evident effect on the minimal and maximal sway motion amplitudes, but it can cause the variation of frequency range of the essential coupled sloshing action. Generally speaking, the vertical baffle is an effective method for suppressing the sway motion response of the sloshing tank in waves.

A new combination approach for optimal design of sedimentation tanks based on hydrodynamic simulation model and machine learning algorithms

The current study aims to propose a novel approach to design rectangular primary sedimentation tanks using computational fluid dynamics (CFD) and artificial intelligence. Hybrid adaptive neuro-fuzzy inference system and particle swarm optimization algorithm (ANFIS-PSO) is trained using CFD model's results. ANFIS-PSO is coupled with two multi-objective algorithms to optimize two objectives: Mean velocity and baffles' configurations. For the single-baffle tank, the optimal baffle position regarding flow velocity was approximately at 0.13 of the basin length, with the height ratio (ratio of baffle height to weir height) of 0.21, but the most cost-effective design was obtained when the single baffle was placed at about 0.06 of total length, with the height ratio of 0.17. Using two baffles could enhance the tank's hydraulic performance, especially when the first and second baffles were at 0.11 and 0.25 of the tank's length, respectively, with the height ratio of 0.33 and 0.22, respectively.

The Baffle Length Effects on the Natural Convection in Nanofluid-Filled Square Enclosure with Sinusoidal Temperature.

The proper process of applying heat to many technological devices is a significant challenge. There are many nanofluids of different sizes used inside the system. The current study combines this potential to improve convection effects, considering numerical simulations of natural convection using Cu/water nanofluids in a square enclosure with bottom blocks embedded in baffles. The enclosure consists of two vertical walls with isothermal boundary conditions; the left wall is the sinusoidal heat source, whereas the right wall is cooled. The investigations dealt with the influences of nanoparticle concentration, Rayleigh number, baffle length, and thermal conductivity ratioon isotherms, stream functions, and average Nusselt number. The results present that, when the Rayleigh number rises, the fluid flow velocity increases, and the heat transfer improves. Furthermore, the baffle length case (Lb = 0.3) provides higher heat transfer characteristics than other baffle height cases.

Impact response of a partially filled fuel tank subjected to high-velocity projectiles

ABSTRACT This study investigates the effects of baffles and various other design changes on a partially filled fuel tank subjected to high-velocity projectile impact. Modelling of the tank filled with water is done using ANSYS software. The Eulerian domain is used to analyse water, whereas the Lagrangian domain is used to assess the tank and bullet. The developed finite element model is verified with available results in the literature. The effect of design parameters like edge fillet, number of baffles, thickness of baffles, orientation of baffles, height of baffles, position of the projectile and projectile speed on the impact responses of the fuel tank is studied. From the analysis results, it could be observed that the edge fillet provided the minimum stress due to the lower stress concentration on the fuel tank, but it was not effective in decreasing the velocity of the projectile. Therefore, the baffles are introduced inside the fuel tanks, which are highly effective in reducing the velocity and generating huge stress on the tanks. The velocity and position of the projectiles are also varied to understand their effect on the fuel tank.

Turbulence and thermo‐flow behavior of air in a rectangular channel with partially inclined baffles

AbstractIn this paper, the thermal performance improvements of a heat removal system like an electronic system have been analyzed. The studied case is a horizontal channel in which two partially inclined baffles are attached with variable height and number. The channel is crossed by a forced convective flow of a cooling fluid (air). This numerical work evaluates the influences of the height and number of the baffles on the enhancement of the heat transfer rate. The mathematical model of this system is composed of nonlinear partial equations that the analytical solution for them is very complex, hence the need for numerical analysis is mandatory with the aid of a finite volume method. Accordingly, The numerical results are presented in axial and transverse velocity, temperature, local and average Nusselt number, local friction coefficient, pressure drop, heat transfer rate, and turbulence kinetic energy. The results revealed that it is possible to improve the thermal performance of the considered system by adopting designs that allow the maximum heat transfer rate with the minimum energy loss. In addition, results show that at the lowest Reynolds number (Re = 10,000), as the height of baffles rises from 0.01 to 0.03 m (growth by 200%), the heat transfer rate augments about 59.09%. Moreover, at the highest evaluated Reynolds number (Re = 87,300), by increasing the height of baffles up to 200%, the heat transfer rate increases by approximately 50.53%. Furthermore, employing a higher number of baffles leads to more heat transfer rates and a significant pressure drop.

Effects of Baffle Height and Baffle Location on Heat Transfer and Flow Profiles in a Baffled Duct: A CFD Analysis

CFD analysis of flow and heat transfer characteristics in a baffled duct is reported. The baffle locations ( s = 0.05 H – 0.40 H ), flow paths (V-apex directing Downstream or VD and V-apex directing Upstream or VU), and baffle heights ( b = 0.05 H – 0.30 H ) are investigated in the laminar flow regime with the Reynolds number based on the entry conditions between 100 and 2,000. Solutions of the present work are obtained by the finite volume method (a commercial code). Key mechanisms such as fluid streams, impinging streams, and disturbed thermal boundary layer in the baffled duct are observed. The baffle locations have high impact on flow and heat transfer behavior. The best heat transfer rate of the baffled duct is 15.55 times higher than that of the general duct with no baffle, while the optimum TEF is 4.06.

Investigation of Effects of Baffle Heights on Flow and Heat Transfer in a Trapezoidal Channel with Vertical Baffles

Bu çalışmada, üst duvarında dik bölmeler bulunan, alt duvarı trapez şeklinde dalgalandırılmış bir kanalda farklı bölme yüksekliğinin akış ve ısı transferine etkileri nanoakışkan ve taban akışkan akışı için sayısal olarak incelenmiştir. Nanoakışkan olarak TiO2 nanopartiküllerin su içerisinde süspansiyonu kullanılmış ve nanopartikül hacim oranı, φ=%1 sabit tutulmuştur. Sayısal çalışma, Hesaplamalı Akışkanlar Dinamiği (HAD) tabanlı FLUENT 15.0 programı ile iki boyutlu gerçekleştirilmiştir. Kanalın bölmeler içeren üst yüzeyinin adyabatik olduğu kabul edilmiş ve alt trapez yüzeyi Tw=360K sabit sıcaklıkta korunmuştur. İki farklı bölme yüksekliği (t=H/2 ve t=2H/3) kullanılarak farklı Reynolds sayıları (200≤Re≤1200) için nanoakışkanın ve taban akışkanın Nusselt sayısı (Nu), sürtünme faktörü (f) ve termo-hidrolik performansı (THP) hesaplanmıştır, ayrıca çalışma bölmelerin olmadığı kanal akışı ile de karşılaştırılmıştır. Kanal içerisinde farklı parametrelerde hız ve sıcaklık görüntüleri elde edilmiştir. Sayısal sonuçlar, trapez bir kanalda bölmelerin yüksekliğine ve nanoakışkana bağlı olarak ısı transferinin önemli ölçüde iyileştiğini, ancak sürtünmenin de bir miktar arttığını göstermiştir. En yüksek termo-hidrolik performans, bölmesiz kanalda taban akışkana göre, TiO2-su nanoakışkan akışında Re=400 ve t=2H/3 bölme yüksekliğinde 1,95 olarak elde edilmiştir.

The influence of baffle geometry on mass transfer and performance of proton exchange membrane fuel cells considering the compression of gas diffusion layer

In this paper, the effects of baffle geometric parameters on fuel cell performance and mass transfer are studied considering the geometric deformation of the gas diffusion layer and the changes in porosity and permeability caused by the assembly force of the stack. The parameters include the windward part length, the middle section length, the leeward part length, the height and the number. We find that changing the windward or leeward part length of baffles will not impact the net power density significantly; short leeward part will produce bimodal streamlines and relatively more power; the baffle height close to blockage is undesirable. In addition, we observe that the trapezoidal baffles can not improve the net power density and the distribution uniformity of the physical quantities inside the fuel cell at the same time.