Porous Screen Research Articles

Porous Material Screening and Evaluation for Deep Desulfurization of Dry Air.

We employ molecular simulations to screen the best microporous materials for deep desulfurization of dry air. Pressure-swing adsorption and temperature-swing adsorption in desulfurization processes are investigated. The selectivity, working ability, selection parameters, and diffusivity of mixed gases are examined to evaluate those materials. The results show that UiO-66, ZIF-71, ZIF-69, and ZIF-97 exhibit good performance for the separation of H2S from air. The selectivity and adsorption capacity of H2S are larger than 300 and 0.01 mmol/g at room temperature and atmospheric pressure, respectively. UiO-66, ZIF-71, ZIF-69, MIL-100, Zn-DOBDC, ZnBDC, IRMOF-11, and MIL-140B are ideal materials to remove SO2 in air. The selectivity of SO2 is higher than 500 and the adsorption capacity is higher than 0.06 mmol/g. The diffusivity of sulfides is determined by the competition between the sterically hindered effect and the intermolecular synergistic effect. Comprehensive analysis found that zeolitic imidazolate frameworks (ZIFs) are good materials for the removal of sulfides.

Heat Transfer-Friction Factor and Correlations for Wavy Porous Screens as Inserts in Channel Thermal Performance

Abstract Structural inserts are employed to enhance the heat transfer in channel flow with the expense of thermal performance. The present investigation employs the wavy porous screens as inserts in an air channel and measures the pressure drop and heat transfer along the channel. The wave vectors are parallel to the flow and in point contact at the tips with the channel walls. The pores in the insert generate turbulence to enhance the heat transfer from the channel walls with a moderate pressure penalty because of the low blockage ratio. The objectives are to investigate the effects of wavelength (λ), porosity (ξ), and height (H) of the sinusoidal wave of the insert as well as the Reynolds number (Re) on the friction factors (f) and Nusselt numbers (Nu). Twelve inserts are formed from the flat metal mesh screens for testing between the Reynolds number (Re) of 400 and 35,000. The results of (f, Nu) and smooth channel-based enhancements (f/f0, Nu/Nu0) are affected the most by Re followed by λ and then ξ. The values of both (f/f0, Nu/Nu0) increase significantly as the Reynolds number increases in Re < 3000. However, both the (f/f0, Nu/Nu0) decrease little as both the (λ, ξ) increase at all Re. The performance factor index, (Nu/Nu0)/(f/f0)(1/3) > 1.0 irrespective of (λ, ξ, H) only when Re is about 3000. The correlations developed for the f, Nu, and performance factor provide reasonable predictions of the experimental results.

Mitigation of liquid sloshing in a rectangular tank due to slotted porous screen

Liquid sloshing inside a tank with a slotted porous screen at the center is studied based on numerical and experimental methods. Slotted screens with three different porosities (0.0964, 0.1968 and 0.3022) for two submergence depths of 1 and 2 cm have been considered. One of the main advantages of the slotted screens is that the resonance frequency of the sloshing tank can be altered and the sloshing-induced motion/load can be suppressed by energy dissipation across the porous screen. The complexities of slotted screens equipped in a sloshing tank are accompanied by wave breaking, jet formation and liquid fragmentations which are commonly seen phenomena across the porous screen. These violent free surface behaviors in a tank are studied based on numerical simulations using the incompressible turbulent model and compared with the experiments. For the numerical sloshing tank with porous screen, free surface elevation and pressure at the tank wall are in good agreement with the experimental results. The adopted numerical technique will be able to capture the nonlinear free surface wave profile, air entrapment and jet formation across the screen in agreement with the experiments. For the fully submerged screen, the lowest resonance period shifted slightly to higher values. The sloshing tank equipped with porous screen of 0.1968 for the fully submerged screen predicted lower values of the amplification factor and pressure at the tank wall compared to other cases.

Simulation on vertical wicking behaviors of liquid hydrogen within metallic weaves in terrestrial and microgravity environments

To predict the wicking performance of liquid hydrogen (LH2) in porous screens, we introduced an evaporative wicking model which has been verified by experiments in liquid nitrogen (LN2). The effects of the fluid properties, the gravity level, the superheated degree and the screen structure parameters on the vertical wicking of saturated LH2 were systematically investigated. The wicking in LH2 performs better than that in LN2, presenting higher maximal wicking height and wicking velocity. At lower gravity, the wicking performance is better in whole but much more sensitive to the changes of superheated condition and structure parameters of the screen. The thermal effect of superheated gas region plays a decisive role in wicking behaviors, significantly reducing the wicking velocity and equilibrium height. The effects of permeability and thickness of the screen are obviously different at superheated condition compared to the isothermal cases.

Liquid sloshing in a rectangular tank with vertical slotted porous screen: Based on analytical, numerical, and experimental approach

The performance of a porous screen placed in the center of a rectangular tank has been investigated based on an analytical, numerical, and experimental approach for the lateral excitation of the tank. The two-dimensional potential model was solved analytically with the Galerkin method by adding the frictional damping coefficient at the free surface condition and considering the energy dissipation across the porous screen. The comparison of the analytical solution with the experimental results shows a good agreement for the frictional damping coefficient of 0.3. The main physical parameters are the surface elevation, pressure at the tank walls, including hydrodynamic forces on the wall, and the horizontal load on the porous screen for different submergence depths and porosities that were investigated. The presence of screen shifts the sloshing tank natural periods slightly, especially in the lowest mode. The unrevealed phenomena accompanied with linear potential theory, the nonlinear wave profile and screen associated effects were also investigated based on an experimental and numerical method. The results show that the numerical prediction with STAR-CCM+ was in good agreement with the experimental results up to second-harmonics. It was found that the porous slotted screen can be an effective device for the suppression of sloshing motion if properly designed.

Experimental study of the hydraulic jump on reverse bed with porous screens

Nowadays, the porous screens have been used extensively in open channels to prevent erosion in ditches as the water in supercritical state flows past the screen which forces the formation of a hydraulic jump upstream of the screen and produces significant energy loss. In this investigation, the operation of screens has been studied for supercritical flow and the Froude number in the range of 4.5 to 10.6 on two reverse slopes experimentally. In this study, the parameters included arrangements of screens in both the single and double types, and the angle and distance of screens from the hydraulic jump toe. The screens were studied with a porosity of about 50% with square holes. The study results showed that using of screens on the reverse slope of − 0.025 dissipates more energy compared to reverse slope of − 0.015. The screens with double arrangement have better performance and dissipate more energy than the screens with single arrangement, while the distance of screens from the toe of the hydraulic jump does not have a significant effect on the energy dissipation.

Study of Heat Transfer from the Shell of Gas Turbine Plant and Methods of Its Thermal Protection

The paper presents the results of determining the temperature of gas turbine plant shell. The total heat transfer from the engine is calculated. The thermal protection scheme by blowing air through the porous screen is proposed to reduce the temperature of the gas turbine plant shell as well as to reduce the total heat transfer from the engine to the surrounding compartment space.

Screen Compliance Experiments for Application of Liquid Acquisition Device in Space

The purpose of a liquid acquisition device (LAD) is to separate liquid and vapor phases inside a spacecraft propellant storage tank in the reduced gravity and microgravity conditions of space so that vapor-free liquid can be extracted to the transfer line. A popular type of LAD called a screen channel LAD or gallery arm, uses a fine porous screen and surface tension forces of the liquid to allow pure liquid to flow through the screen while blocking vapor penetration. To analyze, size, and optimize the design of LADs for future in-space propellant transfer systems, models and data are required for the four fundamental influential factors for LAD systems, including bubble point, flow-through-screen pressure drop, wicking rate, and screen compliance for a wide variety of screen meshes. While there is sporadic data available for three of these parameters, there is no published quantitative data for screen compliance. During the transient startup of propellant transfer, the liquid must be accelerated from rest to the steady flow demand velocity, which causes the screen to deform or comply, so compliance data is required for accurate transient LAD analyses; most design codes only consider steady state analysis. This paper presents screen compliance experiments on 14 different screens, examining the effects of fineness of mesh, open area, and screen metal type on compliance. A basic equation of state is also developed and validated against the data which can be easily integrated into any transient LAD flow code to model propellant transfer.

Experimental investigation on the effect of the duct geometrical parameters on the performance of a ducted wind turbine

This paper reports an experimental investigation on the effect of the duct geometry on the aerodynamic performance of an aerofoil shaped ducted wind turbine (DWT). The tested two-dimensional model is composed of an aerofoil equipped with pressure taps and a uniform porous screen. The experimental setup is based on the assumption that the duct flow is axisymmetric and the rotor can be simulated as an actuator disc. Firstly, different tip clearances between the screen and the aerofoil are tested to point out the influence of this parameter on the DWT performance in terms of aerofoil pressure distribution, aerofoil lift and flow field features at the duct exit area. Then, the combined effect of tip clearance, of the angle of attack and of the screen position along the aerofoil chord is evaluated through a Design of Experiments (DoE) based approach. The analysis shows that, among the analysed range of design factor variation, increasing angle of attack and the tip clearance leads to a beneficial effect on the lift and back-pressure coefficients, while they show a poor dependence upon the screen axial position. Finally, the configuration characterized by the maximum value of all three main factors (15 degree of angle of attack, 5% of tip clearance and 30% backward to the nozzle plane), has the best values of lift coefficient and back-pressure coefficient.

Experimental Measurement of Vortex Ring Screen Interaction Using Flow Visualization and Molecular Tagging Velocimetry

The interaction of vortex rings with thin wire mesh screens is investigated using laser-induced fluorescence (LIF) and molecular tagging velocimetry (MTV). The existence of vortex shedding from individual wires of the porous screens, suggested by prior works, is shown and compared to flow visualization results. A range of interaction Reynolds numbers and screen porosities are studied to determine the conditions affecting the interaction. Transmitted vortex (TV) ring formation is shown to be a function of vortex shedding and the shedding Reynolds number, but not a function of porosity. Screen porosity is shown to affect the TV convective speed but did not impact the formation behaviors. Three major flow regimes existed for the interaction: TV formation with no vortex shedding, TV formation with visible vortex shedding, and no downstream formation with strong shed vortices.

Porous carbon screening for benzene sorption

Benzene is one of the aromatic hydrocarbons that are co‐absorbed with the acid gases during amine scrubbing and are carried over to the catalytic reactors in the sulfur recovery unit where they crack and deactivate the catalyst. As a solution, adsorption of benzene using porous adsorbents is being considered as a suitable process for removal. The present work considers carbon based porous adsorbents as potential adsorbents and attempts to screen the large pool of adsorbents. Preliminary screening was made using information in open literature and structural characteristics, before the adsorbents were subjected to gas phase benzene adsorption. The pool of porous carbons screened included highly acidic sulfonated carbons, ordered mesoporous carbons (OMCs) and various commercial activated carbons (ACs). Among the pool of porous carbons, mesoporous carbon identified as AC1, was found to possess the highest adsorption capacity for benzene with heat of adsorption capacity of 20–32 KJ/mol. It was found that it is possible to regenerate the benzene adsorption capacity of AC1 and a benzene adsorption capacity of about 14 mmol/g for the mesoporous carbon was found to be far superior to the adsorption capacities reported in literature. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S93–S99, 2019

THERMOHYDRAULIC PERFORMANCE OF A CHANNEL EMPLOYING WAVY POROUS SCREENS

Porous inserts are commonly employed in the heat exchanger channels to enhance the thermal performance. The present experimental investigations measure the pressure drop and heat transfer in a rectangular channel that employs a sinusoidally shaped porous screen mesh as inserts. Four screens with different forms of sinusoidal wave are employed: 68% porosity–12-mm period, 48% porosity–12-mm period, 68% porosity–18-mm period, and 48% porosity–18-mm period. The peak-to-peak height of the wave is 5 mm and touches the channel walls along the wave vectors that are parallel to the mean flow. Measurements in the smooth channel are used to normalize the friction factors and Nusselt numbers in the screen channel and provide the enhancements of friction factors f/f0 and Nusselt numbers Nu/Nu0 due to the screens. The Reynolds number Re based on the channel hydraulic diameter varies between 400 and 11,000. The results indicate that the friction factor f, average Nusselt number Nu, Nu/Nu0, and f/f0 in the screen channel depend strongly on Re. The screen porosity and wave period effects are significant on the f and f/f0 only. The thermal performance index, (Nu/Nu0)/(f/f0)(1/3), is also influenced strongly by Re. The present results thus indicate the viability of the wavy porous inserts for heat exchangers.

Hydrophobic and porous cellulose nanofibrous screen for efficient particulate matter (PM2.5) blocking

Particulate matter (PM2.5) pollution in air seriously affects public health. However, both bulk thickness and the accumulation of PM particles typically lead to a quick decline in the air permeability and large pressure drops of the conventional air clean membranes. In this work, we choose cellulose nanofibers (CNFs, a low cost, biodegradable and sustainable material) to form a hydrophobic and porous CNF thin layer on a stainless steel screen (300 mesh with pore size of 48 µm) through a simple filtration-assisted gelation process and subsequent polydimethylsiloxane modification. The prepared hydrophobic CNFs/stainless steel screen demonstrates highly efficient PM2.5 blocking based on size-sieving effect, fast air permeability and long-term durability under natural ventilation conditions in the relative humidity range from 45% to 93%. This technique holds great potential for indoor PM2.5 blocking under natural ventilation conditions.

Glucose Biosensor Based on Immobilization of Glucose Oxidase on Porous Screen Printed Electrodes

Glucose Biosensor Based on Immobilization of Glucose Oxidase on Porous Screen Printed Electrodes

Dry particle generation with a 3-D printed fluidized bed generator

Abstract. Here we describe the design and testing of PRIZE (PRinted fluidIZed bed gEnerator), a compact fluidized bed aerosol generator manufactured using stereolithography (SLA) printing. Dispersing small quantities of powdered materials – due to either rarity or expense – is challenging due to a lack of small, low-cost dry aerosol generators. With this as motivation, we designed and built a generator that uses a mineral dust or other dry powder sample mixed with bronze beads that sit atop a porous screen. A particle-free airflow is introduced, dispersing the sample as airborne particles. Total particle number concentrations and size distributions were measured during different stages of the assembling process to show that the SLA 3-D printed generator did not generate particles until the mineral dust sample was introduced. Time-series measurements with Arizona Test Dust (ATD) showed stable total particle number concentrations of 10–150 cm−3, depending on the sample mass, from the sub- to super-micrometer size range. Additional tests with collected soil dust samples are also presented. PRIZE is simple to assemble, easy to clean, inexpensive and deployable for laboratory and field studies that require dry particle generation.

Experimental validation and model development for thermal transmittances of porous window screens and horizontal louvred blind systems

Virtually every home in the US has some form of shades, blinds, drapes, or other window attachment, but few have been designed for energy savings. In order to provide a common basis of comparison for thermal performance it is important to have validated simulation tools. This paper outlines a review and validation of the ISO 15099 centre-of-glass thermal transmittance correlations for naturally ventilated cavities through measurement and detailed simulations. The focus is on the impacts of room-side ventilated cavities, such as those found with solar screens and horizontal louvred blinds. The thermal transmittance of these systems is measured experimentally, simulated using computational fluid dynamics analysis, and simulated utilizing simplified correlations from ISO 15099. Correlation coefficients are proposed for the ISO 15099 algorithm that reduces the mean error between measured and simulated heat flux for typical solar screens from 16% to 3.5% and from 13% to 1% for horizontal blinds.

Numerical simulation and analysis of hybrid physical-chemical vapor deposition to grow uniform perovskite MAPbI3

Applications of metal halide perovskite have been rapidly developing in recent years. However, very little research focusing on basic growth kinetics of perovskite films can be found in the literature. This paper discusses a hybrid physical-chemical deposition process of planar perovskite films. A 2-D ANSYS Fluent simulation is presented to calculate the heat and mass transfer during the deposition process. An optimized mass flow configuration with a flow resistance imposed by a porous screen is shown to give a uniform distribution of the methylammonium iodide vapor precursor and an even surface deposition rate of perovskite films. Both steady and transient calculations indicate that increasing operating temperature or vessel pressure within certain limits can boost the surface deposition rate of perovskite. Limitations on working pressure are presented for preventing reverse flow into the chamber and associated deterioration of deposition uniformity of the perovskite films.

Velocity Field Visualization in USP Dissolution Apparatus 3 Using Particle Image Velocimetry

PurposeThe hydrodynamics in USP dissolution apparatus 3, at five different dip rates, was characterized by analyzing phase-averaged velocity fields obtained using Particle Image Velocimetry (PIV).MethodsPhase locked 2 Component-PIV (2C–PIV) measurements were recorded on a typical dissolution apparatus 3 configuration with a black painted tablet fixed at the center of the bottom porous screen of the reciprocating cylinder. A trigger mechanism was employed to capture data over 12 phase positions for each reciprocation cycle. Data were captured over a fixed number of cycles, based on dip rate, and the resultant images were post-processed to obtain phase-averaged velocity fields at each phase.ResultsFor all dip rates studied, the sinusoidal nature of the cylinder’s reciprocating motion was evident in the images. The phase positions, in which the cylinder was completely submerged, were characterized by recirculation of liquid through the cylinder, top fitting cap, vessel-cylinder annulus, and bottom fitting cap. The direction of recirculation was opposite for phase positions during the up- and downstrokes. The end positions of the up- and downstrokes were characterized by vortices below and above the cylinder respectively. Increasing dip rates led mainly to increasing velocity magnitudes while all flow characteristics, in general, were retained.ConclusionsThe hydrodynamics in typical USP dissolution apparatus 3 is characterized by cyclic phase-dependent flow fields. Specifically, the velocity field distribution within dissolution apparatus 3 is greatly influenced by the relative position of the top cap to the liquid level in the cylinder.

Geoecoprotective Technologies of Storage of used Wooden Sleepers

The article deals with the negative impact of organic pollution of used wooden sleepers. The research offers geoecoconstruction to protect the environment from such influence. It is shown that such a construction can be made in the form of a porous screen. Design sizes are calculated taking into account the geoecoprotective properties of porous material. Geoecological reliability coefficient is calculated for the geoecoprotective screen.

Experimental study of flow field of an aerofoil shaped diffuser with a porous screen simulating the rotor

This study presents an experimental investigation on a diffuser augmented wind turbine (DAWT). A screen mesh is used to simulate the energy extraction mechanisms of a wind turbine in experiment. Different screen porosities corresponding to different turbine loading coefficients are tested. Measurements of the axial force and of the velocity distribution in radial direction are reported. The general purpose is to highlight the dependency between the diffuser and the screen, and to compare the radial velocity distributions in the diffuser between unloaded and loaded conditions. It is shown that the thrust on an unshrouded screen is lower than on a shrouded screen, under the same inflow condition. Moreover, the thrust on the diffuser largely depends on the screen loading. For the present configuration, the thrust on the screen with high loading coefficient contributes for more than 70% of the total thrust on the DAWT. Smoke visualizations and radial velocity profiles reveal that the high loading screen induces flow separation on the outer surface of the diffuser, justifying the results of the thrust measurements. It is also inferred that the flow separation leads to loss of thrust and has a great effect on the total pressure drag. It should be emphasized that the experimental results indicate that the flow field around the diffuser is strongly affected by the choice of screen porosity, that is, turbine loading. And that, the thrust coefficient of the diffuser does not show a linear dependence on the thrust coefficient of the screen. The axial momentum theory, therefore, is not a solid predictor for DAWT performance with high loaded screens.