Perforated Sheet Research Articles

Slanted septum and multiple folded cavity liners for broadband sound absorption

The design of acoustic liners with complex cavities for a wide frequency range of attenuation using numerical method is investigated in this paper. Three novel liner concepts are presented, demonstrating predicted improvements in broadband sound absorption when compared with that for conventional designs. The liners include a slanted septum core, a slanted septum core with varying percentage open area, and a MultiFOCAL concept. A finite element model of a normal incidence impedance tube is developed using COMSOL Multiphysics modeling software to predict the acoustic properties (resistance and reactance) of liners at medium and high sound pressure levels, and to study the impact of variations in the liner design parameters. The impedance tube finite element model incorporates non-linear semi-empirical impedance equations, validated by comparing numerical results with measurements performed on a single-degree-of-freedom liner, with a perforated face sheet, at high sound pressure level. The design variables of the novel liner concepts are optimized using a hybrid automated optimisation procedure. The low-frequency optimum slanted septum core concept with an open area of 4.5% for the face sheet and 18% for the short slanted septum is predicted to have an absorption level of at least 14 dB in the frequency range of 400–1000 Hz for normally incident pure tone excitations at 150 dB. The slanted septum core concept with varying percentage open area, with broadband optimum design variables, is predicted to have good broadband sound absorption levels of at least 10 dB in the frequency range of 570–3800 Hz. Finally, the MultiFOCAL liner concept with optimised percentage open areas is predicted to have an excellent broadband sound absorption levels of at least 14 dB, for pure tone excitations at 150 dB, in the frequency range of 900–5300 Hz. This work will be followed by optimisation of the face sheet geometries of these novel liner designs in order to maximise lined duct attenuation for aircraft engine applications.

Air Permeability, Shock Absorption Ability, and Flexural Strength of 3D-Printed Perforated ABS Polymer Sheets with 3D-Knitted Fabric Cushioning for Sports Face Guard Applications.

Sports face guards (FGs) are devices that protect athletes from maxillofacial injury or ensure rapid return to play following orofacial damage. Conventional FGs are uncomfortable to wear owing to stuffiness caused by poor ventilation and often slip off due to increase in weight due to absorption of moisture from perspiration, lowering players’ performance. Herein, combinations of 3D-printed perforated acrylonitrile butadiene styrene (ABS) polymer sheets and 3D-knitted fabrics with honeycomb structures as cushioning materials were investigated to balance better wearing feel and mechanical properties. The flexural strength, weight, and shock absorption ability of, and air flow rate through, the ABS sheets with five different perforation patterns were evaluated and compared with those of conventional FG materials comprising a combination of polycaprolactone sheets for the medical splint and polychloroprene rubber for the cushioning material. The ABS sheets having 10% open area and 2.52 mm round holes, combined with knitted fabric cushioning, exhibited the requisite shock absorbing, higher air permeability, and lower weight properties than the conventional materials. Our results suggest that FGs fabricated using combinations of 3D-printed perforated ABS polymer sheets and 3D-knitted fabrics with honeycomb structures may impart enhanced wearing comfort for athletes.

Mechanical behavior of toilet paper perforation

Perforation is used in multilayer tissue products, such as toilet and kitchen papers, as part of the converting process. Perforation facilitates the detachment of consecutive sheets by the user. The compromise between the strength required to detach a perforated sheet and the strength required to break a sheet affects the perforation efficiency. In this work, the mechanical behaviors of 15 commercial papers from different European producers were studied. A morphological analysis of the materials was performed, followed by the determination of their perforation efficiency (through tensile tests). A qualitative analysis of the cuts quality, along with a quantitative analysis of the same cuts dimensions was performed through an optical system. Finally, the stress concentration in the holes and the influence of the cuts distance were analyzed using a finite element model implemented in Abaqus/Standard finite element software. The results showed that a cut distance of 2.0 mm should not be used in these types of papers, and the perforation efficiency increased with the cut distance, regardless of the number of plies in the toilet paper. The stress concentration factor was also determined to have a limit value of 0.11. Papers above this limit value tear at the perforation line, as desired.

Recommended set of interfacial drag correlations for the two-phase flow under thermal–hydraulic conditions of a horizontal steam generator

A set of interfacial drag correlations is proposed for describing two-phase flows under thermal–hydraulic conditions of a horizontal steam generator (SG). This set of correlations takes into account the peculiarities of the two-phase flow in different regions of the SG. Four characteristic regions are considered: tube bundles, tube-free zones in the SG lower part, zone between the outlet from the tube bundles and the submerged perforated sheet (SPS), and the SG upper part. The flow regime map contains bubbly flow, cap-bubbly flow, churn-turbulent flow and mist flow. A two-group bubbly flow model is used to describe bubbly and cap-bubbly flows in the SG corridors/gaps and in the bubbling layer above the SPS. Churn-turbulent flow occurs at the outlet from the tube bundles. In zones with a high void fraction under the SPS and above the SPS, mist flow occurs as a result of steam escaping from the interface with water droplets being captured and carried up. Some coefficients of the correlations are adjusted on experimental data. The detailed description of the set of interfacial drag correlations is presented in the paper. These correlations are implemented in the STEG-M code, which is validated on the experimental data of the void fraction obtained at two slice models of a horizontal SG (PGV and PGV-1500) and the full-scale WWER-1000 SG. Good agreement between the calculated and experimental data is obtained. The mean absolute deviation of the void fractions is <5.0%.

Time-domain simulations of sound propagation in a flow duct with extended-reacting liners

A general methodology to simulate acoustic propagation in ducts with extended-reacting liners in the time domain is presented, including a generic perforated sheet on the air-material interface. The Linearized Euler Equations (LEE) with a mean flow profile are solved in the duct and the linearized equations on an equivalent fluid are solved in the liner material. The auxiliary differential equation method (ADE) is used to prevent the computation of convolution integrals, and leads to a formulation compatible with high-order numerical schemes. The methodology is illustrated for the case of liners consisting of rigid-frame porous materials and a prototype of locally-resonant acoustic metamaterials. A one-dimensional (1D) test case is first used to validate the algorithm and assess the numerical error. The numerical order of the algorithm is the expected one, independently of the interface, as long as the number of poles retained in the partial fraction expansions involved in the formulation is high enough. The algorithm is then applied to a realistic two-dimensional (2D) configuration in a duct with flow, and is used to illustrate the restrained validity of the locally-reacting approximation. Finally, the impact of the flow Mach number on the acoustic performance of porous and metamaterial extended-reacting liners is briefly assessed.

Thermal Analysis of a Solar Hybrid Dehydrator Designed for Uniform Multi-Product Drying

Abstract Thermal analysis was performed for a vertical cabinet solar hybrid dryer having a salient feature of the perforated sheet along its entire height to achieve uniform drying. The dryer was integrated with a solar collector and gas burner for a hybrid heating source. Experiments were performed using tomato at 55 °C with solar, gas, and dual (solar-gas) heating sources. Energy analysis showed that rates of energy utilization were found in ranges of 2.7–12.5 kW (dual), 3–13 kW (gas), and 2.9–12 kW (solar), and energy ratios were 13–56% (dual), 14–58% (gas), and 12–50% (solar). Exergy analysis showed that exergy losses were 2.1–5.0 kJ/kg (dual), 2.1–5.3 kJ/kg (gas), and 1.5–4.2 kJ/kg (solar) while exergy efficiencies found 33–70% (dual), 30–75% (gas), and 20–69% (solar). Based on higher values of exergetic factor and improvement potential rate (IP), it was found that optimization of heating source especially those consisting solar collector and heat exchanger (IP 1.93 kW) is required. The specific energies for the removal of product moisture and to dry the product were found 2.42, 2.72, 2.58 MJ/kg of water and 18.8, 21.2, 20.15 MJ/kg dried product for drying processes conducted under solar, gas, and dual (solar-gas) heating sources, respectively. For design optimization, a complete algorithm has been prepared for complete drying systems in terms of available energy and losses.

Numerical analysis of the equalization capability of submerged perforated sheets for wwer-1500 horizontal steam generator

The results of a study on the equalization of a non-uniform steam load using different submerged perforated sheets (SPSs) are presented for a full-scale horizontal WWER-1500 steam generator (SG). The calculations performed with the STEG code are used. A short description of the 3D thermal-hydraulic code STEG is presented. A new model of gravitational separation based on empirical correlations for the size distribution of water droplets and for the modal droplet diameter is implemented in the STEG code. Three variants of the distribution of an SPS perforation degree are analyzed. Various characteristics are compared: the distributions of the superficial velocity on the SPS and evaporation surface, the fractions of the steam flow rate with high velocity in the steam region and the steam moisture at the outlet from the SG. The SPS perforation degrees, which significantly improve the equalization of the non-uniform steam load, are found using the STEG code.

Correlations between building performances and design parameters of double‐skin facade utilizing perforated screen

AbstractThis study investigates the effect of a perforated sheet combined with a double‐skin facade (DSPF) by varying the important building parameters, such as perforation percentage, facade orientation, and the thickness of the double‐skin facade (DSF). This study determines the energy‐saving, natural ventilation, and daylight performance of an office building in Tokyo, Japan by conducting simulations. This study discovers that the DSPF thickness does not influence the performances much and the DSPF thickness of 0.5 m is recommended. For daylighting, the system with the 40% perforation percentage on the south and 10% perforation percentage on the west is the best case of daylight access without disturbing glare in the particular view of this study. To balance natural ventilation and daylight when installing perforated screens, this research demonstrated the net heat removal in spring when the perforated percentage of 50% on the south and 30% on the west is recommended. In autumn, the net heat removal when the perforated percentage of 10% on the south and 30% on the west is recommended. This research demonstrated that the total net heat removal when the perforated percentage of 10% on the south and 30% on the west are recommended for removing heat throughout a year.

Thermal performance analysis of naturally ventilated and perforated sheet based double skin facade system for hot summer conditions

A new skin of perforated sheets in the cavity of double skin facades (DSF) system is introduced for efficient heat removal from the cavity in hot summer conditions. In this paper, the analytical solution is developed to estimate the thermal performance of the double-skin façade system with and without perforated sheet operating under natural ventilation mode. This analytical model is designed to predict the solar heat gain coefficient (SHGC) for hot summer conditions. An experimental investigation has also been conducted to validate the proposed analytical model. Results showed good agreement between the measured and calculated value of SHGC for DSF system with and without perforated sheet. It is observed that the addition of a perforated sheet reduces the SHGC by nearly 51.5% as compared to DSF system. Perforated sheets enable a better stack effect within the air cavity zone and thereby improve heat transfer characteristics. Therefore, the benefit of the perforated sheet within the air cavity of DSF system is profound over conventional DSF system.

Parametric analysis of factors affecting thermal performance of photovoltaic triple skin façade system (PV-TSF)

This paper optimizes the factors affecting the performance of a photovoltaic triple-skin façade system (PV-TSF) using the Taguchi design of experiments (DOE) method. Input parameters such as air cavity width (A), perforated sheet porosity (B), and outer skin transparency (C) are investigated for the responses (solar heat gain coefficient (SHGC), radiative heat flux (RHF) and illuminance (lux)). Experiments are conducted using the Taguchi's L25 orthogonal array design. The results showed that the optimum conditions for SHGC, RHF, and lux levels are obtained at A3B1C1, A2B1C1, and A1B5 C5, respectively. The transparency of outer skin is most dominant factor for SHGC and lux with a contribution of nearly 54% and 85%, respectively, and perforated sheet porosity with 59.5% contribution is most dominant factor for RHF. The linear regression analysis exhibited a strong direct relationship with high correlation coefficients (R2). Confirmation tests are also performed, which were found within the confidence interval.

Exploring the advantages of photo-voltaic triple skin façade in hot summer conditions

A new skin of perforated metallic sheet is introduced in the cavity of a photo-voltaic double skin façade (PV-DSF) system for an efficient heat removal from the cavity without losing substantial light into the built space. Quantitative experimental analysis is conducted to evaluate its thermal and electrical performance for various combinations of ventilation modes, air cavities, and perforation ratios. The advantages of Photo-Voltaic Triple Skin Facade system (PV-TSF) over commonly used PV-DSF are also evaluated experimentally. The results showed that naturally ventilated PV-TSF provides lower temperatures and Solar Heat Gain Coefficient (SHGC) with slightly higher power when compared to no ventilation mode in PV-DSF system. The SHGC of the PV-DSF system can be reduced by nearly 4.7% with variation in air cavity (Thickness 50–200 mm); after which no noticeable improvement is observed. In the case of PV-TSF system, SHGC can be reduced by almost 14.7% compared to the PV-DSF system without significant loss of natural daylight into built space. Experimental results also showed that the reduction in perforation ratio from 60% to 20% reduced the SHGC by 3.8% with an average illuminance of 334 lux (minimum perforation, 20%). It was also observed that the addition of a perforated sheet can offset the large air cavity of a PV-DSF system. Therefore, the benefit of the PV-TSF system is profound as compared to PV-DSF.

ADVANTAGES OF SCREENING IMBIBITION JUICES

Traditionally, all imbibition juices were screened through perforated sheets and cush cush was conveyed by scraper conveyor cum elevator ahead of mill # 2 in the tandem. With the introduction of DSM screens for the screening of mixed juice, the screening of imbibition juices was also discontinued and these juices were pumped directly along with cush cush through chockless pumps. At Shahtaj, we started screening of imbibition juices which proved to be a great success. In this case study, the advantages / benefits of new adopted system shall be discussed.

Efficient Lipid Bilayer Formation by Dipping Lipid-Loaded Microperforated Sheet in Aqueous Solution

This paper describes a method for a bilayer lipid membrane (BLM) formation using a perforated sheet along with an open chamber. Microscopic observation of the formed membrane showed a typical droplet interface bilayer. We proved that the formed membrane was a BLM based on electrical measurements of the membrane protein α-hemolysin, which produces nanopores in BLMs. Unlike the conventional approach for BLM formation based on the droplet contact method, this method provides aqueous surfaces with no organic solvent coating layer. Hence, this method is suitable for producing BLMs that facilitate the direct addition of chemicals into the aqueous phase.

Thermally Conductive Film Fabricated Using Perforated Graphite Sheet and UV-Curable Pressure-Sensitive Adhesive.

Thermally conductive films play a crucial role in expanding the lifetime of electronics by dissipating concentrated heat to heatsinks. In this work, a thermally conductive film (g-TC film) was manufactured using a perforated graphite sheet (p-GS) and a UV-curable pressure-sensitive adhesive (PSA) by lamination. A novel UV-curable PSA was prepared by incorporating a UV-curable abietic acid ester into a PSA composition. The UV-curable PSA became a tack-free film upon UV irradiation; thus, a flexible g-TC film with a 52-μm thickness was obtained. The defects in the g-TC film caused by air bubbles were removed by treating the p-GS with oxygen plasma. As the UV-cured PSA made a joint through the holes in the p-GS, cleavage of the graphite was not observed after 10,000 U-folding test cycles with a folding radius of 1 mm. The calculated in-plane thermal conductivity of the fabricated g-TC film was 179 W∙m−1K−1, which was stable after the U-folding tests.

Design of Tunable Acoustic Liner and Adaptive Control System

Traditional acoustic liners used in nacelles and fan ducts include a perforated face sheet bonded to a honeycomb core. A tunable acoustic liner with a piezoelectric substrate is developed to overcome the shortages of current liner such as unchangeable structure and uncontrollable bandwidth. After the piezoelectric panel deformed under the driving voltage, the resonant chamber changed, and the resonant frequency shifts. The finite element method is used to calculate the acoustic system’s resonant frequency and sound pressure distribution. The transmission loss measurement was carried out in an impedance tube to demonstrate the broadband noise control effect of the liner. The experiment result indicates that the TL peak frequency keeps linear with the driving voltage, and the sensitivity is measured to be 0.1 Hz/V. A DC amplified circuit using photo resistor is designed based on constructing the function of driving voltage and noise frequency. Benefit from the adaptive algorithm, when the noise frequency offsets from 756 to 788 Hz, the driving voltage can be automatically regulated from 110 to 420 V, and the liner always keeps resonating. Meanwhile, the sound level was reduced. The adaptive noise control is realized for broadband noise reduction.

Compact 2DOF liner based on a long elastic open-neck acoustic resonator for low frequency absorption

Passive acoustic liners, used in aeronautic engine nacelles to reduce radiated fan noise, have a quarter-wavelength behavior. The simplest systems are SDOF-type (single degree of freedom), consisting of a perforated sheet backed with a honeycomb, whose absorption ability is limited to frequencies near the Helmholtz frequency. Thus, to widen the absorption frequency range, manufacturers use a 2DOF (double degree of freedom) system, with an internal layer over another honeycomb (stack of two resonators). However, one constraint is the limited thickness of the overall system, which reduces the space allotted to each honeycomb. A possible approach, based on a previous concept called LEONAR (long elastic open-neck acoustic resonator), could be to link each perforated layer to hollow tubes inserted in each honeycomb layer, in order to shift resonance frequencies to lower frequencies by extending the air column lengths. The presence of an empty chamber on both sides of the internal perforated layer also allows the tube length to be increased through tubes crossing both cavities, preserving the liner thickness. The main aim of this article is to mathematically describe the principle of a 2DOF LEONAR and to show the relevance of the mathematical model through FEM simulations and experiments performed in an impedance tube. Moreover, its behavior is analyzed through a parametric study, in order to explore its potential for an aeronautic application. A remarkable feature of 2DOF LEONAR-type materials with insertion of bottom tubes in the higher cavity is the possibility of maintaining the low frequency band provided by the original LEONAR concept, while adding a second absorption peak at a higher frequency, by the second layer and the accompanying tubes. There is a fundamental difference from classical SDOF/2DOF resonators, for which the thicknesses are obviously different.

Разработка новых заторно-сусловарочно-фильтрационных аппаратов для производства крафтового пива

Introduction. New innovative technologies make food industry more effective. The present paper introduces a new method of hopped wort production based on novel mash filters.&#x0D; Study objects and methods. The research featured two new designs of mash filters. The study of the mashing process involved malt, hops, drinking water, and beer wort. The research included generally accepted methods of physicochemical and sensory research.&#x0D; Results and discussion. Both models differed from the traditional design. Mash filter I had a cylindrical filtration vat at its bottom with filters in the lower and upper parts of the vat. A pump was installed on the outer side of the steam jacket to produce forced circulation of the liquid medium flow through the vat. The steam jacket was covered with Corundum Classic superfine liquid thermal insulation. Mash filter II had a filtration bottom made of perforated sheet and provided intensive liquid circulation. It also had a regulated mixer that moved the mash, which significantly improved the mashing process. After the mashing, the mash passed through the filtration bottom, separating the liquid phase from the solid phase. The crushed material was discharged through a hatch in bottom. The physicochemical and sensory profiles of the obtained beer wort and beer samples complied with State Standard 30060-93 “Beer. Methods for determination of organoleptic indices and product’s volume”. Mash filter II produced beer wort of higher quality and improved the sensory properties of the finished product. This model proved more effective in extracting proteins and digestible sugars during amylolysis due to a better mixing and circulation of liquid medium flow during the wort preparation.&#x0D; Conclusion. The new modified mash filter made it possible to reduce the brewing time by 28.6%. Not only was it more user friendly, but it also was less heat and electricity consuming. In addition, it reduced the production area as it combined the stages of mashing and filtering.

Using a porous-media approach for CFD modelling of wave interaction with thin perforated structures

This work presents the use of a porous-media approach for computational fluid dynamics (CFD) modelling of wave interaction with thin perforated sheets and cylinders. The perforated structures are not resolved explicitly but represented by a volumetric porous zone where a volume-averaged pressure gradient in the form of a drag term is applied to the Navier–Stokes momentum equation. The horizontal force on the structures and the free-surface elevation at wave gauges around the cylinder model have been analysed for a range of porosities and regular wave conditions. The CFD results are verified against results from a linear potential-flow model and validated against experimental results. The applied pressure gradient formulation produces good agreement for all porosity values, wave frequencies and wave steepnesses investigated. It is demonstrated that an isotropic macroscopic porosity representation used for large volumetric granular material can also be used for thin perforated structures. This approach offers greater flexibility in the range of wave conditions that can be modelled compared to approaches based on linear potential-flow theory and requires a smaller computational effort compared to CFD approaches which resolve the flow through the openings. The approach can therefore be an efficient alternative for engineering problems where large-scale effects such as global forces and the overall flow-behaviour are of the main interest.

A new auxetic structure with enhanced stiffness via stiffened elliptical perforations

Auxetic materials, a class of metamaterials with negative Poisson’s ratio, have been extensively studied due to their attractive mechanical properties. In this study, an auxetic material was developed using new perforation shapes with stiffeners. Standard elliptical perforations were stiffened and analyzed by the finite-element method. Periodic boundary conditions were applied to the unit cell of the new shapes and their effective Poisson’s ratio and Young’s modulus were calculated. The finite-element analysis found that the proposed stiffened perforated sheets exhibited auxetic behavior and had enhanced stiffness compared with standard elliptically perforated sheets.

Investigation of the equalization capability of submerged perforated sheets forWWER-1500 horizontal steam generator

Non-uniform heat transfer occurs at the steam generator secondary side, thus inducing a non-uniform steam generation and a non-uniform steam flow rate along the evaporation surface. In order to equalize the steam flow rate, submerged perforated sheet is installed in the horizontal SGs An analysis of the equalization of the non-uniform steam load in the WWER-1500 horizontal steam generator is performed using the STEG calculation code. Variant calculations of various options for the perforation of sheets allowed us to determine the design of submerged perforated sheet, which very well equalizes the initially non-uniform steam load.