Influence Of Baffles Research Articles

Numerical study on heat and mass transfer performance of a natural draft wet cooling tower based on baffle optimization

In the natural draft wet cooling towers (NDWCTs), the resistance of the packing layer to air and the effect of the circular design of its cross-section, the air reaches the tower center area to overcome the maximum resistance. The air velocity in the center of the tower is low and the heat transfer is poor. To improve the performance of the cooling tower, the optimized design of the cooling tower distribution pipe surface with baffles is firstly investigated. Then, the three-dimensional numerical model of NDWCTs is developed and validated with power plant data. Finally, the effect of plates on cooling tower performance is analyzed through the influence of baffles on the cooling tower air field and combined with the circulating water temperature drop, evaporation, and ventilation. Results show that the air field uniformity inside the cooling tower is effectively improved by adding baffles. The cooling efficiency of the circulating water inside the cooling tower is improved. The air velocity in the packing zone is significantly increased by adding the a1a2 type baffle and the air temperature and circulating water in the central area of the tower decreases significantly and the a1a2 baffles performed best in terms of circulating water temperature drop in the packing zone and were able to significantly improve the cooling effect. The cooling tower with pro-wall baffles can cool the circulating water better than the conventional cooling tower. This study provides ideas for subsequent structural and energy efficiency studies.

Study of Baffle Height and Wind Velocity Effect on the Characteristics of Pool Fires in a Wind Tunnel

Wind-blown pool fire accidents in a ventilated tunnel usually pose and present serious risks to properties and personal safety. In this paper, the flame characteristics and flow field changes of pool fires under the combined influence of baffles and crosswinds were investigated using wind tunnel experiments and numerical simulations. The fire experiments reveal that the flame length increases first, then decreases with increasing crosswind speeds up to 3 m/s and then becomes almost constant. Finally, as the wind speed continues to increase, the flame length remains constant. The flame height decreases with crosswind speed up to 3 m/s and then remains almost unchanged. As for the flame tilt angle, the flame above the baffle increases first and then remains unchanged when the velocity of crosswind increases from 2 to 5 m/s. According to the simulation results, the clockwise rotating eddy will be generated downstream of the baffle. The recirculation zone on the surface of the pool transfers the fresh air to the flame. The vortex zone downstream of the pool can retain heat and send back unignited fuel vapor to be burned rather than being blown away. The results may provide beneficial suggestions for understanding flame development behind obstacles for ventilated tunnels.

A 2D low-order thermoacoustic network model of annular combustor with baffles in the plenum

Experimental results showed that configuring different baffles (a regular flat, a single- or double-layer perforated plate and a Helmholtz resonator) in the plenum can well suppress the self-excited oscillation in annular combustor. In this paper, a 2D low-order network model is proposed to describe this phenomenon and predict the modal frequencies and growth rates of longitudinal and circumferential thermoacoustic modes for annular combustor with different baffles. In the plenum, only the circumferential acoustic propagation and the influence of baffles on it are accounted for as the longitudinal geometry size is much smaller than the acoustic wavelength of the longitudinal mode. Pure longitudinal acoustic propagation is considered in burners and both longitudinal and circumferential ones are accounted for in the combustion chamber. These three modules are connected by jump conditions. The numerical prediction matches the experimental results. Baffles using Helmholtz resonators feature the best damping performance. The circumferential mode is converted to two unfolded non-degenerate modes when configuring perforated plates baffles. Best damping effect for the configuration of the baffles in the plenum can be achieved based on the proposed model.

Numerical simulation of half-full cylindrical and bi-lobed storage tanks against the sloshing phenomenon

This paper examines sloshing dynamics in cylindrical and bi-lobed liquid storage tanks including horizontal cylinders, vertical cylinders, horizontal bi-lobes, and vertical bi-lobes. The influence of baffle was evaluated, and the analysis presented accounts for sway induced hydrodynamic force as the criterion to compare different scenarios. To do this, the sloshing phenomenon was modeled by OpenFOAM based on coupled RANS solver and VOF method, and the RANS equations were discretized by the Finite Volume Method, and solved by using the PIMPLE algorithm. Finally, an engineering method suggesting the find the best dimension of the tank and baffle for the case of a cylindrical and bi-lobed tanks is presented to minimize the horizontal force exerted along the tank motion.

Numerical Simulation on Windage Power Loss of High-Speed Spur Gear with Baffles

Windage power loss (WPL) is significant and cannot be neglected in a study on transmission efficiency and reducing the energy consumption of high-speed gear. The influence mechanism of the baffle on the reduction of WPL needs to be further studied. Based on computational fluid dynamics (CFD) technology, this paper puts stress on analyzing the influence of axial and radial baffles on viscous and pressure effects in WPL and the influence of baffles with groove structures on reducing WPL. The numerical calculation model of windage torque considering the baffle’s regulation is established, and the calculation results of WPL with different baffle configurations are obtained. The results indicate that the radial baffle mainly reduces pressure loss, while power loss caused by the viscous effect is mainly affected by the axial baffle. The baffle with the smallest clearance achieves the most significant suppression effect on windage. On this basis, adding groove structures to a smooth baffle can have a positive or negative impact on reducing WPL, and the baffles with circular grooves can further promote the reduction of WPL by 8.2%, compared with smooth baffles. This paper provides a reference for the optimal design of baffles in engineering applications.

Study on the influence of baffles on the aerodynamic coefficients of long-span flexible bridge section

In the study of wind resistance performance of Bridges, the study of aerodynamic coefficients directly affects the accuracy of wind resistance performance of bridges. In this paper, the aerodynamic coefficients of main girder section of single-tower single-side suspension curve suspension cable footpath bridge are studied by numerical simulation and wind tunnel test. In order to improve the wind resistance performance of the bridge, the aerodynamic performance of the bridge section was improved by optimizing the bridge section and adding baffles, and the aerodynamic coefficient was obtained by wind tunnel test. The first section in your paper

Numerical Study on the Effect of Transverse Baffles on the Stability of Iron Concentrate in a Cargo Hold

Cargo fluidization is one of the main causes of ship capsizing accidents, which has been concerned by International Association of Classification Societies. Iron concentrate is regarded as the research object, its movement in the cargo hold is simulated using discrete element method. To effectively reduce the sloshing amplitude of cargo in the cargo hold, four conditions that considering the transverse baffles are designed. The stability of cargo is analyzed in detail from the offset of cargo gravity center and the contact force on the bulkhead induced by the cargo movement. Numerical simulation results show that the installation of transverse baffles can effectively reduce the sloshing amplitude of cargo in the cargo hold. Especially, it can better restrain the variation of center of gravity of cargo in the y-direction. The study focuses on the influence of baffles with different lengths on the stability of cargo in the cargo hold, which can provide a reference for the prevention of bulk carrier accidents.

Influence of baffles on mixing and heat transfer characteristics in an internally heated rotating drum

Baffles can effectively improve the mixing and heat transfer in internally heated rotating drums. To explore the performance of baffles, discrete element method (DEM) is employed in this work, and the influence of the placement and length of baffles on the mixing and heat transfer in an internally heated drum is investigated. The simulation results show that a central cross baffle promotes the mixing and heat transfer significantly, and the optimal length varies with material properties, for example, at the length-to-diameter ratio L/D = 0.4 for monodispersed glass particles, 0.6–0.7 for binary glass-steel mixtures. The peripheral baffle generally weakens the mixing and heat transfer performance, and effects only for a sufficiently long peripheral baffle at the length-to-radius ratio L/R = 0.9. Baffles promote the heat transfer process and do not change the thermal contribution of heat transfer paths.

An optimization of microtube heat exchangers for supercritical CO2 cooling based on numerical and theoretical analysis

This paper presents a new simulation method with lower computation consumption for microtube heat exchangers (MSTEs) used for supercritical CO2 cooling, which maintains high precision. The heat transfer characteristics in the shell pass and tube pass and the relationship between them are both analyzed. Baffles lead to various regions with different follow patterns and heat transfer features in the shell pass. Furthermore, higher heat transfer performance in the shell pass leads to heat transfer enhancement in the tube pass due to the CO2 near-pseudocritical characteristics. The optimization method based on the eigenfunction of ΔPi = F(Ai) which characterizes the influence of baffles on the comprehensive performance of MSTEs focuses on the difference among local heat exchange and pressure loss in multiple segments and guides to reduce the pressure loss while the heat transfer load and area remain unchanged. The optimized baffles arrangement is found according to the numerical results and the optimization method. The comparison between the simulation results of the original and optimized MSTEs shows that the optimization method is effective for heat exchangers with variable local heat exchange features and pressure loss performances.

Computational investigation of baffle influence on windage loss in helical geared transmissions

The calculation model of enclosed helical gear is established to investigate the effect of baffle arrangements and clearances on windage loss, and the multivariate interactions of the baffle features for windage loss are examined. The results elucidate that the outlet and bilateral baffle configurations have roughly equal contributions on reducing windage loss, while the inlet baffle contributes less. The joint effect of the outlet and radial clearance was largely higher than that of each alone on windage loss; while for the outlet and inlet clearance, the individual effects were significantly stronger. These results indicate that the windage loss and flow mechanism of gear channel are mainly dominated by axial outlet baffle and radial baffle, rather than by axial inlet baffle.

Performance evaluation of thermoelectric generator using CFD

The aim of this study is to analyze various ways to increase the performance of Thermoelectric (TEG) by using Computational Fluid Dynamics (CFD) techniques. For this study a three-dimensional model of TEG is developed using design modeling software SOLIDWORKS and the developed geometry is exported to CFD package which is ANSYS-FLUENT for further analysis. Mass flow rate of exhaust gas is 0.279 kg/s at a temperature of 800 K and mass flow rate of the coolant is 0.26Kg/s at a temperature 350 K are taken as boundary conditions. For this analysis various parameters are investigated such as heat exchanger material, inclination and exit gap of heat deflector and use of baffles. The effect of heat exchanger material on the performance of TEG is investigated. For this investigation pure copper, pure aluminum, aluminum alloy and low-carbon steel are chosen as heat exchanger material. Results show that pure copper has given better performance than others with 184.98 K of temperature difference. To study the effect of exit gap between heat deflector and exhaust pipe on TEG performance, exit gap is varied from 10 mm to 15 mm with an increment of 2.5 mm. The inclination angle of heat deflector is varied from 1° to 3.5° with an increment of 0.5°. Results show that 2°inclination angle of deflector with 10 mm exit gap has given better performance than other inclinations and exit gaps. The influence of baffles on TEG performance is also studied. Introducing a baffle in inclined position directs the flow direction of exhaust gas effectively to achieve better heat distribution. Finally, it can be concluded TEG has good performance with copper material as heat exchanger material, 2° inclination angle of deflector and 10 mm exit gap between heat deflector to the exhaust pipe.

Numerical analyses of the influence of baffles on the dynamics of debris flow in a gully

After the 2008 Ms 8.0 Wenchuan earthquake, a huge amount of loose debris materials were accumulated on the surface of slopes in the mountainous areas of Southwestern China. Under heavy rainfalls and earthquakes, these loose debris materials can flow, washed away, and subsequently enter the mountainous rivers due to landslides and debris flows. They can change the sediment supply of the river channel and result in the adjustment of riverbed. To mitigate the adverse impacts, baffles are usually installed on slopes in front of the protected areas to reduce the kinetic energy of incoming debris flows. In order to clarify the interacting mechanism between debris materials and baffles structure, the dynamics of granular transportation and deposition in a typical gully have been analyzed via the three-dimensional discrete element method (DEM). The numerical results indicate that the arrangement of baffles (e.g., spacing distance, layout row, and height) has a significant influence on the dissipation of debris energy and the final sediment deposition pattern. The kinetic energy, the velocity of granular flow, and the total mass of debris materials entering the river channel decrease with the increase of the baffles lateral spacing distance, layout row, and height. Correspondingly, the amount of debris materials retained by the baffles will increase. Thickness and volume of particle deposits in the upstream region increased with increase in lateral spacing, rows, and height of the baffles, but decreased in the downstream area. In addition, the baffle configuration can affect the particle size distribution along the channel. The results of this research can provide a theoretical basis for baffle designs and the prevention of debris flows in mountainous areas.

CFD simulation of the aeration process and baffle influence in a full-scale commercial flat sheet module

The goal of the present paper is to investigate the aeration process and the enhanced effect of baffles in a full-scale commercial membrane bioreactor (MBR) system configured with a flat sheet (FS) membrane module. Through a computational fluid dynamics (CFD) simulation, two aerated FS membrane modules for full-scale applications with 26 membrane sheets were simulated. The numerical results indicate that the presence of baffles and the distances between the baffle and the outmost membrane sheet have a minor influence on the area-weighted shear stress for full-scale MBRs. In addition, bubble size and the bottom distance between the aerator and membrane bottom do not affect the average shear stress of full-scale FS membrane modules much. However, an increase in air flow rate has a significant effect on the area-weighted shear stress. A large FS membrane module is recommended, as it could achieve the same cleaning effect as the small one with a lower specific aeration demand for membranes.

Investigation of influence of baffles on landslide debris mobility by 3D material point method

In mountainous terrain, landslide debris is a common occurrence around the world that can potentially result in catastrophic consequences to downstream residents and facilities. Arrays of baffles are increasingly used as energy dissipaters for the protection from debris flow due to their low cost and environmental impact. However, the development of a numerical tool for the rational design of such structures is still a challenge. In this work, a material point method computational framework is presented, using two contact models to describe the landslide debris movement and interaction with structures, respectively. Flume model experiments are adopted as calibration and good agreements are exhibited in flow kinematics between computed results and physical model tests. Simulations on an idealized scenario of landslide debris flow show how the baffle geometry/arrangement has key effects on the debris movement and deposition. The impact force in soil-structure interaction has also been studied, showing the ability of this method on evaluation force characteristics acted on baffle structures.

Thermal Behaviour Analysis of Baffled Multi Heat pipe Induced Heat Exchanger

Thermal behaviour of a multi-heat pipe induced in compact heat exchanger has been analysed with the influence of baffles. The heat transfer fluid and working fluid used for the investigation are water and acetone. In this investigation, baffles are used to improve performance. In this research, different parameters like temperature range of hot and cold water were 50ºC, 60ºC, 70ºC and 32ºC throughout the analysis. The mass flow rates of hot and cold water ranges as 40 LPH to 120 LPH and 20 LPH to 60 LPH with an increase of 20 LPH and 10 LPH. The result shows that for an optimum revealed conditions of an angle of 0º with 60ºC and 100 LPH there is an increase in effectiveness occurs as 82.05% while comparing to without baffled conditions.

Computational investigation of hydrodynamics and solid circulation in fluidized bed column

Gas–solid fluidized beds are commonly used in applications where high heat and mass transfer is required, which are influenced by the quality of mixing in the bed. This largely depends on the design of gas distributor and operating conditions. Hence, in the current work, the influence of distributor design on hydrodynamics in a 3D bubbling fluidized bed column is investigated using CFD. Here, Euler-Euler model is used to predict the flow field. The predicted bed pressure drop is analyzed for various superficial gas velocities, and it has been validated with the experimental data. The solid circulation rate is calculated to quantify the flow field, and it is improved by incorporating various gas distributors such as flat, convex and concave perforated plates. The magnitude of solid circulation rate is found to be the highest for convex plate, showing that it is more advantageous than the conventional flat plate configuration. Further, the effect of operating temperature and the influence of baffle on gas–solid flow are analyzed. The rate of solid circulation is found to decrease with increase in temperature and in the presence of baffle.

Numerical simulation of the influence of baffles on the impact force of heavy-duty tanker

The impact force of heavy-duty tanker is simulated and analyzed under liquid sloshing. Based on the finite volume method, the free liquid level capture technology (VOF) is used to establish a numerical calculation model for the sloshing analysis of heavy liquid tank trucks. FLUENT, a fluid simulation software, is used to simulate the impact of liquid on the front head of liquid tanker when the braking acceleration is 0.981m/s2, and the filling ratio is 0.5. The influence was studied that the number of rectangular baffles brings the changes of the impact force of the front head of the liquid tanker. The research provides a reference for the optimization design of baffles in heavy oil tanker manufacturers in the future and also validates the rationality of baffle set in the latest national standards.

Numerical analysis on gas-solid mixing in ceramic dry granulation room with baffles

In order to investigate the influence of baffles on the mixing effect of particles during ceramic dry granulation process.Air-particles interaction was analyzed by euler gas-solid two phases flow model, the granulation area was simplified.The three dimensional physical model of particles mixing process was constructed, granulation room rotary motion was simulated by sliding grid method and multiple reference frame method, turbulent motion was analyzed by modified RNG discrete model. The influence of different baffles on particles mixing was investigated according to the volume fraction distribution and velocity field, changed the position of the baffle can increase the blending effect by about 22%.The results showed: when there were no baffles, wall baffles and middle baffles in the granulation room, the average volume fraction of powder was about 0.22, 0.18 and 0.26 respectively. The average speed of powder was about 0.6m/s, 0.9m/s and 0.4m/s respectively. The wall baffle made the powder have significant axial movement, the experimental data showed: when granulation room had wall baffles, the content of active particles accounted for about 73%. It is helpful to improve the understanding of gas-solid two phase flow field in ceramic drying granulation room and provide some theoretical guidance for the design and optimization of the baffle.

Numerical studies on the effect of baffle on the heat transfer and flow in cross-corrugated triangular ducts

The cross-corrugated triangular ducts are suitable for plate heat exchanger because of its high heat transfer capability and strong mechanical strength. In this numerical study, a SST k-ω model is used, 6 different cases for installing different baffles in the cross-corrugated triangular ducts are involved. The frict ional resistance and heat transfer coefficient in the 1000-6000 range of Reynolds number are studied, the influence of baffle on flow-pattern and temperature distribution are analyzed. Combined with the comprehensive heat trans fer index, a good improvement plan was proposed. The results show that baffle can effectively increase the heat transfer area, change the mainstream direction, enhance the fluid disturbance, and enhance the heat transfer. In addition, case 6 is the best enhanced heat transfer scheme. Compared with the case without the baffle, the Nu of case 6 is 1.5-1.6 t imes that of the original duct, and the heat transfer efficiency can be increased by 13% under the same fan power. It is a feasible choice to set up baffles in the middle and lower part of the upstream channel of the cross-corrugated triangular plate flow channel.

Influence of baffles on upstream passage of brook trout and brown trout in an experimental box culvert

There is much to learn about improving baffle designs to increase successful fish passage through culverts. A fish’s motivation to attempt entry into the culvert is essential. Upon entry, successful passage will largely depend on the physiological ability of the fish to navigate the entire culvert length. In this study, the motivation of brook trout (Salvelinus fontinalis (Mitchill, 1814)) and brown trout (Salmo trutta Linnaeus, 1758) to attempt ascent of an experimental flume, which mimics a roadway culvert left bare (smooth) or fitted with either spoiler or weir baffles, is assessed. Performance, measured as maximum distance of ascent within the flume, is also quantified. The bare flume was the most motivating for brook trout, and the weirs were most motivating for brown trout. As a rule, brown trout showed less motivation to stage attempts than brook trout, except within the weir baffle treatments. Performance was greatest in the weirs for smaller trout and in the spoiler baffles for larger trout. Our findings suggest that baffle form influences passage rates at road crossings in ways previously unknown and further stresses the importance of considering fish motivation and performance together when assessing the efficacy of baffle forms.