Cylindrical Baffle Research Articles

Effects of an Annular Baffle on Heat Transfer to an Immersed Coil Heat Exchanger in Thermally Stratified Tanks

Abstract The effect of a cylindrical baffle on heat transfer to an immersed heat exchanger is investigated in initially thermally stratified tanks. The heat exchanger is located in the annular region created by the baffle and the tank wall. Three different cases of initial thermal stratification are explored, and in each case, experiments are conducted with and without the baffle in the stratified tank and in a comparable isothermal tank with the same initial energy, enabling exploration of the role of the baffle in a stratified tank and the role of stratification in tanks with or without the baffle. The baffle maintains the high initial temperature of the upper zone of the stratified tank for 10–16 min, as cool plumes that form on the heat exchanger are confined to the annular baffle region until they exit at the bottom of the tank. Regardless of stratification, the baffle always improves heat transfer to the immersed heat exchanger. In the isothermal tanks, the baffle increases total energy extracted in the first 30 min of discharge by over 20%. In stratified tanks, the baffle increases total energy extracted in 30 min of discharge by 9–16%. Initially, improvement in heat transfer in stratified tanks is due to the higher driving temperature differences around the heat exchanger. Later, after all the water from the hot zone has entered and flowed through the baffle, the tank is basically isothermal, and velocity increases as the fluid temperature drops, maintaining rates of heat transfer higher than that in the tank without the baffle. Stratification improves heat transfer in tanks without a baffle because, by design, the driving temperature difference between the heat exchanger wall and the surrounding fluid is considerably higher. However, in tanks with the baffle, stratification has only a modest positive effect on heat transfer to the immersed heat exchanger.

Frequency-invariant direction-of-arrival estimation of circular acoustic vector sensor array for wideband signals on the cylindrical baffle

This passage discusses a method for estimating the DOA (direction-of-arrival) of broadband signal targets on the surface of a cylindrical baffle using a circular acoustic vector sensor array and based on the Minimum Variance Distortionless Response (MVDR) algorithm with joint processing of sound pressure and particle velocity. The approach employs a cylindrical baffle scattering sound field model and, according to the theory of frequency-invariant response, transforms signals at various frequency points within the bandwidth of the circular acoustic vector sensor array. It uses the transformed sound pressure and different velocity components to construct the sound pressure and particle velocity cross-covariance matrix. The spatial correlation between sound pressure and velocity components is utilized to suppress isotropic noise fields. Subsequently, the extended cross-covariance matrix for the summed and vertically arranged broadband signals is obtained, followed by singular value decomposition and reconstruction. Finally, the reconstructed cross-covariance matrix is employed for MVDR beamforming to achieve DOA estimation of targets under cylindrical baffle conditions with frequency-invariant response. Simulation and experimental data processing results indicate that, for broadband DOA estimation with a circular acoustic vector sensor array under cylindrical baffle, the joint processing of sound pressure and particle velocity using the MVDR method exhibits stronger noise suppression capabilities and higher DOA estimation performance compared to the Nehorai method. Additionally, for the joint processing of broadband signal sound pressure and particle velocity, vertically arranged cross-covariance matrices outperform summed cross-covariance matrices in terms of DOA estimation performance.

Novel design and numerical investigation of a windward bend flow field for proton exchange membrane fuel cell

3D flow field design usually improves the performance of proton exchange membrane fuel cell (PEMFC) with the penalty of a dramatically increasing pressure drop. To surmount this issue, a novel windward bend flow field that exhibits superior mass transfer performance under a constant pumping power is proposed in this study. The performance of PEMFC with windward bend flow field is numerically compared with two canonical 3D flow fields, namely 3D wave flow field and cutting cylindrical baffles flow field. Results demonstrated that compared with two canonical 3D flow fields, windward bend flow field gets a better water management capability. The optimal distance, tilt angle and direction for the windward bend structure embedded in channel are 2.0 mm, 15° (at the direction of the front section of the windward bend structure tilts towards membrane electrode assembly). Furthermore, the average enhancement rate of the maximum power density of PEMFC with optimal windward bend flow field is 7.6 % and 12.4 % compared with cutting cylindrical baffles flow field and 3D wave flow field owing to the larger Sherwood number of optimal windward bend flow field under the specified pumping power range.

Underwater soundfield visualisation using directionally constrained acoustic parameters.

This paper presents an underwater soundfield visualisation method for passive-sonar applications employing circular hydrophone arrays. The method operates by segregating the space by means of beamforming into angular sectors scanning the whole horizontal plane and then computing acoustic parameters within each sector. The information from these directionally constrained parameters is fused in order to produce spatial spectra which depict the distribution of acoustic energy over bearing. The evaluation is performed on simulated data of circular hydrophone arrays mounted on rigid cylindrical baffles. Comparisons against baseline methods of similar computational complexity suggest that, for moderate to high signal-to-noise ratio levels, the proposed method offers improved performance in terms of background noise suppression, angular resolution, and direction-of-arrival estimation accuracy. Additionally, it is demonstrated that, with the appropriate choice of sector pattern, the proposed method can, at least in some cases, achieve superior performance to the baseline methods in the presence of interferers even at low signal-to-interference ratio levels. Last, the sector-based parameter diffuseness, which is directly related to the direct-to-diffuse ratio, may be used both as a weight function to further attenuate the background noise level and as a confidence measure of the estimation accuracy.

Method of acoustic separation on the surface of cylindrical baffle

This paper suggests a statistically optimal near-field acoustic holography method based on the combination of plane waves and cylindrical waves, which is used for underwater cylindrical baffles. The method addresses the issue that the extraction of scattered acoustic waves from the surface of underwater cylindrical baffles requires too many measurement points in practical applications: separation of incident and dispersed sound fields and near-field measurements of sound fields at baffle surfaces.The underwater detection sound source is situated in the scatterer's far-field region, so in the actual application scenario for the surface acoustic scattering separation of the cylindrical baffle, the plane wave expansion is used to represent the surface incident acoustic wave and the cylindrical wave expansion is used to describe the scattered acoustic wave on the baffle surface. As a result, fewer expansion orders are required to describe the entire sound field on the baffle's surface. It is verified by simulation that the method is valid and efficient for near-field total sound field measurement and dispersed sound field separation of roughly cylindrical targets under underwater far-field incidence situations because the measurement holographic surface of the surface permits unlimited geometries.

Acoustic radiation from a baffled finite shell in an underwater waveguide

Analytical modelling of vibroacoustic systems can help us to understand the physical phenomena involved in more complex problems, and it provides a benchmark solution and reference upon which more complex systems can be built. In the present work, the system of interest consists of a finite elastic cylindrical shell inserted in infinitely rigid cylindrical baffles and immersed in an underwater acoustic waveguide. The latter consists of a finite fluid layer bounded by an upper free surface and a lower rigid floor. In such a fluid domain, the acoustic waves radiated from the excited shell will exhibit reflections off the boundaries. This phenomenon is modelled by the image-source theory and embedded in the fluid loading term, which intervenes in the shell equations. Investigations into the influence on the finiteness of the elastic shell, types of supports (i.e., simply supported, clamped, free, and combinations of these), and depth of the waveguide on the shell’s acoustic radiation are presented.

Investigation of a novel Couette flow with cylindrical baffles

The high-precision measure instrument for flow velocity is essential for industrial applications because the high-precision velocity can well reflect the physical characteristic of the flow. A restricted laminar Couette flow with cylindrical baffles, using a synthetic heat conduction liquid, was designed to obtain a steady vortex flow and wider work scope, according to Couette flow and Suspension flow characteristics. The heat transfer mechanism was investigated with a laminar flow model by the Fourier law. The research indicates that the heat transfer enhancement is related to the Temperature Boundary Layer (TBL). The TBL is affected by the Velocity Boundary Layer (VBL). The TBL thickness and Nusselt number (Nu) have a dependent relationship. The Reynolds number (Re) and the gap between the baffle and plate wall (Δh/h) can further affect Nu. The vortex flow generated by Couette flow can significantly enhance the heat transfer performance by a double spiral structure, which can rapidly mix heat fluxes and make the temperature converge to uniform. There is a sensitive and stable relationship between flow velocity and heat transfer. Notably, it is linear when Δh/h or Re is small, which can be used to design a high-precision thermal flow velocity meter.

Thermohydraulic performance of a semi-alternated twisted tape insert and cylindrical baffles in a tube with ternary nanofluid under sinusoidal wall temperature

This study numerically evaluates the thermohydraulic performance of a circular tube consisting of semi-alternated twisted tape mounted with cylindrical baffles and ternary nanofluid (SiO2 + ZnO + CaO) as a working fluid. The circular tube wall was exposed to a sinusoidal temperature that axially varied along the wall. The investigation was performed in the laminar flow regime over the Reynolds number 500–2000 and for nanofluid volume fraction 0.01%-0.05%. The semi-alternated twisted tape has pitch ratio 1.77–5.77, width ratio 0.38–0.68 and thickness ratio 0.019–0.033. The performance was analyzed for Nusselt number, pressure drop, thermal performance factor and pumping power. The results indicate, no significant pressure drop increment with volume fraction of the ternary nanofluid. For a fixed volume fraction of 0.01%, width ratio of 0.48 and thickness ratio of 0.019, there is an improvement in Nusselt number by 35–107%, pressure drop increased from 0.26 Pa to 3.5 Pa, pumping power was found to increase by 40%, and thermal performance factor by 1.35–1.67 times that of the smooth tube, when the pitch ratio decreases from 5.77 to 1.77. For a fixed pitch ratio of 1.77 and width ratio 0.38–0.68, the Nusselt number increased by 50–114%, pressure drop increased from 0.207 Pa to 11.1 Pa and thermal performance factor by 1.18–1.76 times as compared with smooth tube. The Nusselt number increased by 100–115% and thermal performance factor increased from 1.08 to 1.16 times the performance of the smooth tube when the thickness ratio was increased from 0.019 to 0.033.

Multi-scale flume investigation of the influence of cylindrical baffles on the mobility of landslide debris

Debris flows travel downslope at high speed and often cause damage to the infrastructure of societies around the world. With increasing extreme rainfall events and urbanization in mountainous regions, effective structural countermeasures are in increasing demand. Over recent years, engineers have proposed the installation of an array of cylindrical columns, called baffles, to reduce the velocity of debris flows in catchments. However, existing design methods are highly empirical in nature, so it is unclear whether they are adequate or over designed, and appropriate specifications and arrangement of cylindrical baffles have still not been suggested. Moreover, previous experimental studies have predominantly modeled debris flows as dry granular flows at a laboratory scale. In this study, to investigate the effect of cylindrical baffles on the dynamic characteristics of debris flow, a series of small-scale flume tests was conducted using a flume equipped with devices to measure the flow interaction between baffles and the dynamic loads of debris flow. In addition, to investigate the scale effect of debris flows and cylindrical baffles on flow characteristics, large-scale tests were also performed according to different numbers of rows of baffles for similar baffle configurations confirmed by small-scale tests. Using the small- and large-scale test results, this study analyzed the energy dissipation and dynamic impact characteristics according to the height and number of rows of baffles. The analysis results showed that the use of baffles increased the energy dissipation of debris flows, and an additional row of baffles produced greater effects on the energy dissipation in the debris flows. Based on the test results, the average dynamic pressure coefficient for cylindrical baffles was 0.31.

Numerical investigation of baffle shape effects on performance and mass transfer of proton exchange membrane fuel cell

Flow channels with baffles can enhance the transport of reactants and improve the performance of proton exchange membrane fuel cell (PEMFC). In this study, five different structures of flow channels with baffles are proposed, and the mass transfer and cell performance of PEMFC with different baffled channels are compared by CFD method. The results show that the PEMFC with a cutting cylindrical baffle has the best performance with an output current density of 1.82 A/m2 when the voltage is 0.4 V. Baffle design can promote reaction gas transmission while also increasing reaction gas concentration in the channel. Due to the circular arc surface design of the cylindrical section, the mass transfer enhancement effect of cutting baffles is better. When the fluid passes through the baffles, the velocity magnitude also changes abruptly due to the disturbance effect, and the more effective convection brought about by the reactants being pushed into the catalytic layer can enhance the mass transfer in the PEMFC and obtain better performance. The presence of baffles will increase the accumulation of water, the smaller the cross-sectional area, the better the water removal effect. Vortex generation will result in large parasitic power, which is detrimental to the performance of the PEMFC.

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.

Flume investigation of cylindrical baffles on landslide debris energy dissipation

Flume investigation of cylindrical baffles on landslide debris energy dissipation

The Effect of Pitch on Heat Transfer to an Immersed Heat Exchanger in a Solar Thermal Storage Tank With and Without a Baffle

Abstract The effect of the pitch of a copper coil heat exchanger immersed in a hot water storage tank on heat transfer from the storage tank to the heat exchanger working fluid is investigated. The storage tank is initially quiescent and full of hot water. The heat exchanger located at the top of the tank has a coil diameter just under the tank diameter and has a pitch of 2, 3, 4, 6, or 12 times the heat exchanger diameter, D. The effect of the pitch is explored both with and without a cylindrical baffle, which creates an annular region with the tank wall that has a width of 1.5D and within which the heat exchanger is located. In experiments without the baffle, increasing the heat exchanger pitch improves the rate of heat transfer to the working fluid. The improved heat transfer is attributed to the increased thermal stratification generated by the larger pitches. In experiments with the baffle, the results for experiments with pitches of 2D, 3D, 4D, and 6D are all very similar, with 3D slightly outperforming the others. Heat transfer to the heat exchanger with a 12D pitch was significantly lower than the others. In experiments both with and without the baffle, the larger pitches resulted in more variation in experimental results, despite strict standards for initial and operating conditions. As in the prior work, the presence of the baffle resulted in significantly higher heat transfer rates compared to respective experiments without the baffle.

DEVELOPMENT AND RESEARCH OF THE TOPOLOGY OF COOLING BAFFLES FOR BLADES OF THE AXIAL CARBON DIOXIDE TURBINES

Currently, there is an increase in average annual temperature and climate change across the various continents. Carbon dioxide emissions from energy facilities contributed to this condition. Implementation of oxy-fuel cycles is a promising solution for reducing carbon dioxide emissions from the energy sector. To date, the most efficient oxy-fuel cycle is the Allam cycle. In this cycle supercritical carbon dioxide acts as a working fluid of the cycle, wherein СО2’s temperature upstream of the turbine is 1,150 °С and the pressure is 30 MPa. Due to the high temperature of the working fluid, it is necessary to cool first stages of the carbon dioxide turbine. The feature of considered cooling system in this turbine is that carbon dioxide being used as a refrigerant too. This paper investigated two topologies of convective cooling systems in the carbon dioxide turbine’s nozzle blade as well as considers an option for increasing the intensity of heatexchange through the use of helical ribbing in the cylindrical cooling baffle. Numerical simulation involving the ANSYS software package was performed for two topologies of the cooling baffles arrangement in the nozzle blade body: configuration 1 -with 17 baffles of 1 mm diameter, configuration 2 -with three baffles of the blade profile shape. Configuration 1 proved to be more efficient: the Nusselt number has a value of 117, and average value of the heat transfer coefficient on the refrigerant side is 6,413 W/m2∙K. The effect of using helical ribbing in the cooling cylindrical baffle of the blade under study was investigated, which enabled to reduce the metal temperature by 54 °С on average and doubled the heat transfer coefficient.

CFD Simulation of a New Dynamic-Static Stirred Model and Its Application in the Leaching Process of Chromite

In the liquid phase oxidation leaching process of chromite salt, a new dynamic-static combined stirred mode is proposed. That is, a static cylindrical baffle is fixedly installed at a certain radius from the stirred blade to control the vicinity of the blade. The CFD numerical simulation method is mainly used to investigate the effect of dynamic-static combined mode on the flow field distribution. Meanwhile, the velocity distribution and trailing vortex near the blade are analyzed. Finally, the differences between traditional stirred blade and dynamic-static combined stirred blade in the oxidation leaching process of chromite are compared. The results show the new dynamic-static combined stirring mode can effectively improve the flow field distribution, reduce the occurrence of “dead zones” in the flow, and increase the chromite leaching efficiency. The leaching time can be reduced from 300 to 240 min, and the chromium-leaching rate has reached up to 99%.

Role of gas coal in sulfur regulation from the release behavior and mass transfer condition of volatiles

There were new restrictions on sulfur regulation of high organic-sulfur coal (HOSC: A) brought by the differences in the pyrolysis characteristics of different gas coals (GC: B and C) and the mass transfer conditions of their volatiles. Firstly, the role of volatiles from GC in the sulfur regulation along vertical and horizontal directions was revealed by designing two stacking modes in a cylindrical crucible and using the parallel and cylindrical baffles to block the volatiles’ migration. Secondly, the different performances of volatiles from two different GC on the sulfur regulation were associated with their volatiles’ release behaviors. And finally, the effect of mass transfer conditions of volatiles on the sulfur regulation was discussed and reflected in the sulfur spatial distribution in chars. Contrast experiments with or without parallel and cylindrical baffles indicated that the monodirectional migration of volatiles from GC helped reduce the sulfur contents along both vertical and horizontal directions. The maximum distances of effective sulfur removal by volatiles from GC along vertical and horizontal directions varied respectively within 5 ∼ 15 and 8 ∼ 15 mm as changing GC. The performance of different GC in sulfur removal depended on the good match of its intensive volatiles release to the high permeability of HOSC and the continuous supply of hydrogen-rich volatiles. The effective distance of bi-directional vertical migration of volatiles was shortened to 3 ∼ 6 mm. It was promising to use the effective distance of sulfur removal by volatiles migrating vertically to evaluate the potential of GC as a sulfur regulator. The bi-directional migration of volatiles from GC helped extend the effective distance in the horizontal direction (>15 mm), which was related to the temperature gradient. The proper temperature gradient helped the volatiles of GC spontaneously or forcedly complement the hydrogen-rich volatiles in the HOSC layer. The temperature gradient is promising to maximize the potential of GC as a sulfur regulator and break the limits on sulfur removal by GC’s volatiles.

Ограниченные цилиндрическим отбойником изгибные колебания составного тяжелого горизонтального вращающегося вала

Drilling of wells, especially inclined and horizontal ones, is accompanied by the intense interaction of drilling tools with the borehole walls. Inborehole impacts negatively affect the drill pipe connections, electrical connections, strength characteristics of downhole motor structural elements, etc. The impact interaction of a drilling tool with a well is experimentally studied using a test bench, where the drilling tool sample is fixed in the middle of a heavy composite shaft arranged in cylindrical roller bearings. The rotating shaft is involved in the impact interaction with a cylindrical baffle due to bending vibrations. In this paper, a beam model of the described shaft is used to study the effect of the rotation speed, gravity forces, damping, and unbalance on the shaft motion. The research is carried out numerically using the ANSYS engineering software package. It is shown that the gravity forces shift the line of centers of gravity in shaft sections, relative to which it rotates. Damping, which is proportional to the speed, provides the shaft centering. The imbalance of the shaft causes bending vibrations. The possible modes of the shaft motion and the conditions for unstable motion are revealed. The mode of the shaft motion within a cylindrical baffle that ensures a steady periodic impact interaction is determined. This interaction induces elastic waves of the acceleration, transverse force and moments in the shaft.

Optimal array layout of cylindrical baffles to reduce energy of rock avalanche

Optimal array layout of cylindrical baffles to reduce energy of rock avalanche

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar

Discussion of “Cylindrical Central Baffle Flume for Flow Measurement in Open Channels” By Aniruddha D. Ghare, Ankur Kapoor, and Avinash M. Badar