Perforated Metal Plate Research Articles

High current density operation of proton exchange membrane fuel cells at a constant relative humidity

To further reduce the size and cost of proton exchange membrane fuel cells, it is desired to operate at high current densities exceeding 2 A/cm2, and consequently achieve power densities above 1 W/cm2. In a prior one-dimensional modeling study that employed the Engineering Equation Solver (EES), it was suggested that proton exchange membrane fuel cells might operate at current densities as high as 10 A/cm2 and even more when appropriate operating and channel dimensions are chosen, and perforated metal plates are used as porous transport layers instead of carbon fiber papers. The current study verifies the general findings of the previous 1-D model by a 3-D multiphase computational fluid dynamics model in Ansys CFX to obtain additional insights. Operating a proton exchange membrane fuel cell at a constant humidity (100%, 80%, 60%) from the inlet to the outlet at the cathode side appears feasible, and results for a current density above 6 A/cm2 were obtained. This mode of operation is promising also for automotive applications.

High current density operation of proton exchange membrane fuel cells at a constant relative humidity

To further reduce the size and cost of proton exchange membrane fuel cells, it is desired to operate at high current densities exceeding 2 A/cm2, and consequently achieve power densities above 1 W/cm2. In a prior one-dimensional modeling study that employed the Engineering Equation Solver (EES), it was suggested that proton exchange membrane fuel cells might operate at current densities as high as 10 A/cm2 and even more when appropriate operating and channel dimensions are chosen, and perforated metal plates are used as porous transport layers instead of carbon fiber papers. The current study verifies the general findings of the previous 1-D model by a 3-D multiphase computational fluid dynamics model in Ansys CFX to obtain additional insights. Operating a proton exchange membrane fuel cell at a constant humidity (100%, 80%, 60%) from the inlet to the outlet at the cathode side appears feasible, and results for a current density above 6 A/cm2 were obtained. This mode of operation is promising also for automotive applications.

High Current Density Operation of a Proton Exchange Membrane Fuel Cell with Varying Inlet Relative Humidity—A Modeling Study

This paper focuses on proton exchange membrane fuel cell (PEMFC) operation at current densities in the order of 6 A/cm2. Such high current densities are conceivable when the traditional carbon fiber papers are replaced with perforated metal plates as the gas diffusion layer to enhance waste heat removal, and at the same time the relative humidity inside the fuel cell is kept below 100% by applying appropriate operating conditions as was found in previous one-dimensional modeling work. In the current paper, we applied a three-dimensional, multi-phase computational fluid dynamics model based on Ansys-CFX to obtain additional insight into the underlying physics. The calculated pressure drops are in very good agreement with previous one-dimensional modeling work, and the current densities in all case studies are in the order of 5–6 A/cm2, but different from the previous one-dimensional study, the results suggest that the relative humidity is very close to 100% throughout the entire channel length when the inlet relative humidity is 100%, ensuring best hydration cell conditions and hence best performance. Importantly, the model results suggest that fuel cell performance at a high current density in conjunction with relatively low stoichiometric flow ratios around 1.5–2 is possible.

Analytical Modeling of Microwave Transmission Through Metasurfaces Made of Perforated Metal Plates, Arrays of Metal Patches, and Wire Grids

Analytical Modeling of Microwave Transmission Through Metasurfaces Made of Perforated Metal Plates, Arrays of Metal Patches, and Wire Grids

Design and Characterization of an Upscaled Dielectric Barrier Discharge-Based Ten-Layer Plasma Source for High-Flow-Rate Gas Treatment

Dielectric barrier discharge (DBD)-based technology is considered a promising alternative for controlling indoor air pollutants. However, its limited processing capacity and lack of design techniques have restricted its use in practical applications. This paper introduces a methodology for designing upscaled DBD reactors with a processing capacity of up to 1000 L/min for treating high-flow-rate gases to mitigate indoor air pollution. A ten-layer high-flow-rate DBD reactor was constructed, with fundamental characterizations, including electrical and spectroscopic measurements, conducted to verify the feasibility of the proposed methodology. In particular, the flow paths of the ten-layer DBD reactor were optimized by incorporating an air diffuser and perforated metal plates, all without significant modifications. Computational fluid dynamics simulations showed a remarkably improved velocity uniformity (0.35 m/s to 0.04 m/s, as evidenced by the velocity standard deviation) in the 10 flow channels. These simulation results were consistent with the experimental results, wherein the velocity standard deviation reduced from 1.38 m/s to 0.13 m/s. Moreover, multi-gas plasma ignition for up to six gas species and high-flow-rate plasma generation of up to 1000 L/min were achieved. These results provide the foundation for developing DBD technologies for practical applications in high-flow-rate gas treatment, particularly for controlling indoor air pollution.

Visualization of a jet stream group influencing the noise increase phenomena in generated by airflow through a perforated metal plate

The perforated plate is made by a punching process. Because of this manufacturing process, the cross section of holes in a perforated plate varies in the direction of the thickness of the plate. When an airflow passes through a group of holes in a perforated plate, the noise characteristics change depending on the direction of passage. In the case where the cross-sectional area of holes increases in the downstream direction, the aerodynamic noise generated by airflow through holes in perforated plates increases. The cause of the noise increase is considered to be the lock-in phenomenon between the vibration of the plates and the outflow of the vortex. For this to occur, at least seven closely spaced groups of holes are required. In this study, flow visualization using the fog method was performed to clarify the behavior of the jet stream group during the noise increase. The results showed that the vortex outflows at each hole were in opposite phase when the lock-in phenomenon did not occur, but that the vortex outflows at adjacent holes were synchronized when the lock-in phenomenon occurred.

Study on thermal performance of a new combined perforated Metallic/Asphalt solar air heater for heating Applications: An experimental study

Using accessible infrastructures and combining different solar air heater types is a novel approach that reduces environmental footprints. The current study investigates a new combined collector, including perforated metallic and asphalt air heaters. The asphalt heater utilizes accessible infrastructures and does not require extra space, while the perforated heater can be integrated with buildings composed of perforated metallic plates. Hence, a combined collector was constructed, and two scenarios were considered for air mass flow rates of 0.0085 kg/s and 0.014 kg/s. The acquired results illustrate that the asphalt heater preheated the flowing air to 61 °C and 58 °C, while the perforated heater continued heating to 85 °C and 76 °C. The asphalt heater started heating with a delay in the morning but continued heating in the afternoon using stored energy during daytime hours; however, the perforated heater started heating right after sunrise and stopped about in the afternoon. During diurnal hours, the asphalt heater gained 51 % of the total heat gain, while the perforated heater gained nearly 49 %. The introduced strategy causes the combined heater operates within a band of 5 % around the peak temperature for a long period, especially in the afternoon, when its efficiency reaches nearly 80 %.

Interaction of weak shock waves with perforated metal plates

Interaction of weak shock waves with perforated metal plates

Study on the wrinkling behavior of perforated metallic plates using uniaxial tensile tests

The Yoshida buckling test (YBT) is a commonly used method to evaluate the wrinkling behavior of sheet metals; however, it is difficult to reflect the actual in-plane stresses in many sheet forming processes owing to the limited variation in the stress state. Furthermore, the test is impracticable for some low-ductility materials because fracture typically occurs before wrinkling. This paper proposes an approach for examining the wrinkling properties of sheet metals using uniaxial tension of plates with a central cut-out; a relevant wrinkling model is established using stress analysis of a finite perforated plate and an energy method. The results show that the typical stress distribution modes around the central hole before wrinkling are biaxial compression in the top/bottom domains and biaxial tension in the lateral domains, and the mode changes with the hole size and tensile displacement. The ratio of transverse to axial stresses increases with the diameter/width ratio; this leads to a larger influence of transverse nonuniform compressive stress, consequently decreasing the critical wrinkling stress. The wrinkling tendency in perforated sheets is more sensitive than that in a conventional YBT specimen; thus, it can be used to capture the subtle distortion of wrinkling for low-ductility materials. A second wrinkling phenomenon that occurred in plates with large holes under a large tensile displacement was observed and addressed.

On the acoustic transparency of perforated metal plates facing a porous fibrous material

Abstract Thin impervious layers, cloths or perforated plates are usually utilized with fibrous absorbing materials in order to avoid small particles, coming from deterioration over time or from flow abrasive effect, becoming dislodged and polluting the environment. These protective facings are to be carefully considered and analyzed, since they can affect the acoustical behavior of the “backing” material. This study addresses this issue through an experimental survey and a theoretical analysis using the Transfer Matrix Method (TMM). Experiments have been performed in the frequency range 160–2,500 Hz, analyzing the different behaviors due to multiple combinations of percentage of open area and air gap between perforated facing and absorbing material. Experimental data have shown a marked effect of the percentage of perforation, at least up to a threshold value of 20%, whereas the air gap slightly affected the acoustic behavior of the covered absorbing material. The TMM was applied to the tested faced absorbing system, and experimental and theoretical results were compared, showing the good accuracy of the model. Several geometrical configurations were then modeled through TMM and the possibility of using this method in order to assess the acoustic transparency of perforated metal plates was assessed.

Underwater acoustic surface waves on a periodically perforated metal plate.

Acoustic surface waves are supported at the surface of appropriately structured elastic materials. Here the excitation and propagation of the lowest-order surface mode supported by a square array of open-ended cavities on a metal plate submerged in water is demonstrated. This mode, which has a half-wavelength character in the cavity, arises due to inter-cavity interaction by evanescent diffraction of the pressure field, and forms a band from zero-frequency to an asymptotic limit frequency. The authors perform an acoustic characterization of the pressure field close to the surface of the perforated plate in the 60-100 kHz frequency range; sound is pulsed from a fixed point-like acoustic source, and the evolution of the acoustic field across the sample surface is measured as a function of time and space with a traversing detector. Using Fourier analysis, the dispersion is imaged between points of high-symmetry (Γ,X,M) and at planes in momentum-space at fixed frequencies. Beaming of acoustic energy on the surface over a narrow frequency band was observed, caused by the anisotropic mode dispersion of the acoustic surface wave on the square lattice. The measured dispersion shows good agreement with the predictions of a numerical model.

Two-Dimensional Imaging of Permittivity Distribution by an Activated Meta-Structure with a Functional Scanning Defect

A novel 2D imaging method for permittivity imaging using a meta-structure with a functional scanning defect is proposed, working in the millimeter wave-range. The meta-structure we used here is composed of a perforated metal plate with subwavelength-holes and a needle-like conductor that can scan two-dimensionally just beneath the plate. The metal plate, which is referred to as a metal hole array (MHA) in this study, is known as a structure supporting propagation of spoof surface plasmon polaritons (SSPPs). High-frequency waves with frequencies higher than microwaves, including SSPPs, have the potential to detect signals from inner parts embedded beneath solid surfaces such as living cells or organs under the skin, without physical invasion, because of the larger skin depth penetration of millimeter wave-bands than optical wave-bands. Focused on activated SSPPs, the localized distortion of SSPP modes on an MHA is used in the proposed method to scan the electromagnetic properties of the MHA with a needle-like conductor (conductive probe), which is a kind of active defect-initiator. To show the validity of the proposed method, electromagnetic analyses of the localized distortions of wave fields were performed, and one- and two-dimensional imaging experiments were conducted with the aim of detecting both conductive and dielectric samples. The analytical results confirmed the localized distortion of the electric field distribution of SSPP modes and also indicated that the proposed method has scanning ability. In experimental studies, the detection of conductive and dielectric samples was successful, where the detected dielectrics contained pseudo-biological materials, with an accuracy on the order of millimeters. Finally, a biomedical diagnosis in the case of a rat lung is demonstrated by using the experimental system. These results indicate that the proposed method may be usable for non-invasive and low-risk biomedical diagnosis.

Dual-Band Dual-Polarized Quasi-Elliptic Frequency Selective Surfaces

A structure for the design of dual-band dual-polarized quasi-elliptic frequency selective surfaces (FSSs) is proposed in this letter, whose unit cell is composed of multiple arrays of cylindrical dielectric resonators with capped annular ring resonators inserted in a perforated metallic plate. The designed FSS provides quasi-elliptic filtering responses with two transmission poles (TPs) in the passbands and two transmission zeros (TZs) in the upper stopbands. So does it for an incident wave with either TE- or TM-polarization in each band. In addition, the frequency responses including center frequencies, TPs/TZs, and the input impedance of the propagating path matched to the free space in each band can be tuned separately to achieve the best filtering performance.

Noise increase phenomenon of the air flow through a perforated metal plate

Noise increase phenomenon of the air flow through a perforated metal plate

Ant lion optimizer for optimization of finite perforated metallic plate

Minimizing the stress concentration around hypotrochoid hole in finite metallic plates under in-plane loading is an important consideration in engineering design. In the analysis of finite metallic plate, the effective factors on stress distribution around holes include curvature radius of the corner of the hole, hole orientation, plate\'s aspect ratio, and hole size. This paper aims to investigate the impact of these factors on stress analysis of finite metallic plate with central hypotrochoid hole. To obtain the lowest value of stress around a hypotrochoid hole, a swarm intelligence optimization method named ant lion optimizer is used. In this study, with the hypothesis of plane stress circumstances, analytical solution of Muskhelishvili\'s complex variable method and conformal mapping is employed. The plate is taken into account to be finite, isotropic and linearly elastic. By applying suitable boundary conditions and least square boundary collocation technique, undefined coefficients of stress function are found. The results revealed that by choosing the above-mentioned factor correctly, the lowest value of stress would be obtained around the hole allowing to an increment in load-bearing capacity of the structure.

Surgical approach to flail chest: 3 clinical cases

Introduction Flail chest is a severe life threatening injury with mortality rates reaching up to 33%, traditionally treated with mechanical ventilation (“internal fixation”). Recently, some authors recommend a surgical approach for highly unstable flail chest. Several rib fixation techniques have been described although none are considered gold standard. Despite growing evidence of benefits for both the patient as well as the hospital, there is a general reluctance to perform rib fixation. In smaller hospitals such as the one referred to in this text, general surgeons are called to manage these patients and as such, it is a prerequisite of their training to be aware of all available treatment options, including standard and novel surgical solutions for flail chest injury. Case description The 3 cases involved polytrauma victims who have undergone emergency laparotomy because of abdominal injuries. Rib osteosyntheses were undertaken once the patients were haemodynamically stable. Perforated metal plates and screws were used in all cases. All patients were readily weaned off from ventilation with no post-surgical complications from the osteosynthesis and were subsequently discharged home well. All patients remain asymptomatic and no complications were registered during a 17 months (average) follow up. Conclusion Surgical fixation of fractured ribs is a straightforward procedure which promotes reestablishment of ventilatory dynamics. Despite several studies favouring the surgical approach to flail chest, many surgeons are still reluctant to perform this procedure. The authors present a simple and reproducible technique, with good results.

Capped Dielectric Inserted Perforated Metallic Plate Bandpass Frequency Selective Surface

A capped dielectric inserted perforated metallic plate is proposed to design wide-bandpass frequency selective surface (FSS). The proposed structure is using the conventional perforated metallic plate with certain thickness inserted by a series of capped circular dielectric resonators, which satisfies tight mechanical requirements of applications such as huge dichroic mirror. Comparing with the conventional perforated metallic plate, it exhibits much more stable frequency response under oblique incidence of wide angles. An equivalent circuit modal is presented using the even–odd mode method, and the calculated frequency responses are discussed with variation of different parameters and they are in good agreement with the full-wave simulated results. Finally, an FSS is designed based on the discussed structure. The FSS is tested, and the measured frequency responses agree well with simulated ones. Measurements show that the minimum insertion loss is 0.31 dB at the two transmission poles under normal incidence, and insertion loss is 0.5 dB at the center frequency of the passband. The fractional 3 dB bandwidth is 20% under the normal incidence. In addition, the wideband filtering performance for both TE and TM polarizations can be obtained under various oblique incidence angles up to 40°.

Thin structured rigid body for acoustic absorption

We present a thin acoustic metamaterial absorber, comprised of only rigid metal and air, that gives rise to near unity absorption of airborne sound on resonance. This simple, easily fabricated, robust structure comprising a perforated metal plate separated from a rigid wall by a deeply subwavelength channel of air is an ideal candidate for a sound absorbing panel. The strong absorption in the system is attributed to the thermo-viscous losses arising from a sound wave guided between the plate and the wall, defining the subwavelength channel.

Simple estimation of effective elastic constants for thin plates with regular perforations and an application to the vibration of distillation column trays

The horizontal perforated sheet metal plates are commonly used in the process industries as trays in distillation columns, important internal parts for fractionating the input liquid mixture. Normally, the operating performance of such trays is satisfactory. However, cases have been reported of abnormally high levels of tray vibration during operation at particular conditions. The trays then experienced fatigue cracking accompanied by the loosening of bolts and fixings, which led to expensive failures. The excitation of structural resonance was suspected as a component in flow-induced vibration. Using linear stress superposition, a simple but robust analytical method is developed to provide high-quality predictions for the stress and strain distributions for in-plane loaded thin perforated plates with periodic hole arrangements. This approach is built on the classical solution for the elastic stress field around a single circular hole in a large plate. The perforated plates with square penetration patterns are investigated in this article, although the same approach is applicable to any regular penetration pattern. Stress concentration factors as well as the effective elastic constants, which can be used to describe the bending properties of the perforated plates, are then verified against both the established theoretical solutions and the results from finite element simulations. Excellent agreement to both previously published physical experiments and complex modelling is observed in all cases, with small-to-medium (up to 40%) hole-area fraction. The proposed analytical method is much simpler and computationally efficient than finite element analysis. The computed effective elastic constants are used in a finite element modal analysis to estimate the free vibration frequencies of a stiffened distillation column tray example; the first 30 vibration modes are found to be almost uniformly distributed between 25 and 70 Hz, which matches the vibration frequency range reported from plant operations.

Management of post-sternotomy mediastinitis in cardiac patients

Post-sternotomy mediastinitis is a severe complication of cardiac surgery and accompanied by high mortality and cost of treatment. To date, there are no large clinical trials defining treatment of these patients. In this study the authors offer early postoperative wound sanitation, use of vacuum drainage in all cases and surgical repair with local tissues. Sternal destruction is cured by osteosynthesis with wire sutures and perforated metal plates. Proposed algorithm showed low incidence of reccurent wound infection, mortality and duration of treatment.