Perforated Tube Research Articles

SHAPE OPTIMIZATION OF MULTI-CHAMBER SIDE INLET/OUTLET MUFFLERS HYBRIDIZED WITH MULTIPLE PERFORATED INTRUDING TUBES USING A GENETIC ALGORITHM

The use of perforated-tube side mufflers for depressing venting noise within a constrained space has been prevalent in modern industries. Also, research on mufflers equipped with side inlets/outlets has been thoroughly documented. However, research on shape optimization of side inlet/outlet mufflers hybridized with multiple open-ended perforated intruding tubes which may enhance acoustic performance has gone unnoticed. Therefore, we wish to not only analyze the sound transmission loss (STL) of side inlet/outlet mufflers but also to optimize their best design shape within a limited space. In this paper, the generalized decoupling technique and the plane wave theory used in solving the coupled acoustical problem are employed. Also, a four-pole system matrix for evaluating acoustic performance is deduced in conjunction with a genetic algorithm (GA). We have also introduced a numerical study that deals with broadband noise within a constrained blower room using three kinds of mufflers. Additionally, before muffler shape optimization is performed, an accuracy check on the mathematical models has been performed. Moreover, to verify the reliability of the GA optimization, optimal noise abatements for various pure tones on various mufflers have been examined. Results reveal that mufflers equipped with perforated intruding tubes are superior to those equipped with non-perforated intruding tubes. Also, mufflers with multi-perforated tubes will increase the acoustic performance. Consequently, the approach used in seeking the optimal design of the STL proposed in this study is quite effective.

Improvement of two-phase refrigerant distribution in a parallel flow minichannel heat exchanger using insertion devices

In this study, various insert devices (wire mesh, perforated plate, perforated tube) were investigated to obtain an improved flow distribution in a round header/ten flat tube test section using R-134a. To simulate an actual brazed aluminum heat exchanger, tubes were protruded to center of the header. Tests were conducted both for downward and upward flow for the mass flux from 70 to 130 kg m−2 s−1 and quality from 0.2 to 0.6. Of the investigated insert devices, perforated tube significantly improved the flow distribution both for downward and upward flow when the holes were located facing tubes. Preferred hole geometry was dependent on the flow direction. For downward flow, non-uniform hole configuration with decreasing hole sizes in flow direction yielded better flow distribution than uniform hole configuration. For upward flow, however, uniform hole configuration yielded better flow distribution. Possible reason was provided based on flow visualization results. Header pressure drop was obtained from the measured pressure drop by subtracting appropriate pressure drops. For no-insert configuration, header pressure drops were mostly negative, which implied that the pressure was recovered in the header. With insertion of the perforated tube, however, the header pressure drop increased significantly. Other insert devices (wire mesh, perforated plate) were not effective in improving the flow distribution.

Characterisation of microbial activity in the framework of natural attenuation without groundwater monitoring wells?: a new Direct-Push probe

At many contaminated field sites in Europe, monitored natural attenuation is a feasible site remediation option. Natural attenuation includes several processes but only the microbial degradation leads to real contaminant removal and very few methods are accepted by the authorities providing real evidence of microbial contaminant degradation activity. One of those methods is the recently developed in situ microcosm approach (BACTRAP®). These in situ microcosms consist of perforated stainless steel cages or PTFE tubes filled with an activated carbon matrix that is amended with 13C-labelled contaminants; the microcosms are then exposed within groundwater monitoring wells. Based on this approach, natural attenuation was accepted by authorities as a site remediation option for the BTEX-polluted site Zeitz in Germany. Currently, the in situ microcosms are restricted to the use inside groundwater monitoring wells at the level of the aquifer. The (classical) system therefore is only applicable on field sites with a network of monitoring wells, and only microbial activity inside the monitoring wells at the level of the aquifer can be assessed. In order to overcome these limitations, a new Direct-Push BACTRAP probe was developed on the basis of the Geoprobe® equipment. With respect to the mechanical boundary conditions of the DP technique, these new probes were constructed in a rugged and segmented manner and are adaptable to various sampling concepts. With this new probe, the approach can be extended to field sites without existing monitoring wells, and microbial activity was demonstrated to be measureable even under very dry conditions inside the vadose zone above the aquifer. In a field test, classical and Direct-Push BACTRAPs were applied in the BTEX-contaminated aquifer at the ModelPROBE reference site Zeitz (Germany). Both types of BACTRAPs were incubated in the centre and at the fringe of the BTEX plume. Analysis of phospholipid fatty acid (PLFA) patterns showed that the bacterial communities on DP-BACTRAPs were more similar to the soil than those found on classical BACTRAPs. During microbial degradation of the (13)C-labelled substrate on the carrier material of the microcosms, the label was only slightly incorporated into bacterial biomass, as determined by PLFA analysis. This provides clear indication for decreased in situ natural attenuation potential in comparison to earlier sampling campaigns, which is presumably caused by a large-scale source remediation measure in the meantime. In conclusion, Direct-Push-based BACTRAPs offer a promising way to monitor natural attenuation or remediation success at field sites which are currently inaccessible by the technique due to the lack of monitoring wells or due to a main contamination present within the vadose zone.

A 3-Stage Treatment System For Domestic Wastewater: Part I. Development

This study presents the development of a micro-scaled 3-stage wastewater treatment system applicable to small volume domestic effluents. The primary components of the system include 1) Spiral-Framed Human Hair-Based Filter, 2) Plastic Medium Mixed Flow Biotower, and 3) Pistia Stratiotes-Based Free Surface Water Wetland System. The first stage Spiral-Framed Human Hair-Based Filter consists of an oil and grease removal apparatus filled with human hair blocks and operated in a spiral plane aimed at removing emulsified oils from wastewater. The process is followed by a second stage Plastic Medium Mixed Flow Biotower filled with perforated cylindrical plastic tubes in horizontal and vertical arrangements to provide alternate vertical and cross flows for removal of suspended solids, ammoniacal-nitrogen, and biochemical oxygen demand. The effluent would then be channelled to the free surface water wetland system (third stage) filled with Pistia Stratiotes (water lettuce) for removal of nutrients such as nitrogen, phosphorus, and potassium from wastewater. From this study, it was found that Human Hair-Based Filter could remove 73.54% emulsified oils from wastewater, while the combined removal efficiencies of Plastic Medium Mixed Flow Biotower and Free Surface Water wetland system operated in series recorded 59.2% biochemical oxygen demand, 87.9% ammoniacal-nitrogen, 90.6% nitrogen, 54.9% phosphorous, 68.5% potassium, and 59.0% turbidity.

Preliminary Laboratory-Scale Model Auger Installation and Testing of Carbonated Soil-MgO Columns

Abstract This paper presents details of the installation and performance of carbonated soil-MgO columns using a laboratory-scale model auger setup. MgO grout was mixed with the soil using the auger and the columns were then carbonated with gaseous CO2 introduced in two different ways: one using auger mixing and the other through a perforated plastic tube system inserted into the treated column. The performance of the columns in terms of unconfined compressive strength (UCS), stiffness, strain at failure and microstructure (using X-ray diffraction and scanning electron microscopy) showed that the soil-MgO columns were carbonated very quickly (in under 1 h) and yielded relatively high strength values, of 2.4–9.4 MPa, which on average were five times that of corresponding 28-day ambient cured uncarbonated columns. This confirmed, together with observations of dense microstructure and hydrated magnesium carbonates, that a good degree of carbonation had taken place. The results also showed that the carbonation method and period have a significant effect on the resulting performance, with the carbonation through the perforated pipe producing the best results.

Internal Erosion during Soil Pipeflow: State of the Science for Experimental and Numerical Analysis

Keywords: Ephemeral gully erosion Erodibility Internal erosion Landslides Pipeflow Soil pipes. Abstract. Many field observations have led to speculation on the role of piping in embankment failures, landslides, and gully erosion. However, there has not been a consensus on the subsurface flow and erosion processes involved, and inconsistent use of terms have exacerbated the problem. One such piping process that has been the focus in numerous field observations, but with very limited mechanistic experimental work, is flow through a discrete macropore or soil pipe. Questions exist as to the conditions under which preferential flow through soil pipes results in internal erosion, stabilizes hillslopes by acting as drains, destabilizes hillslopes via pore-pressure buildups, and results in gully formation or reformation of filled-in ephemeral gullies. The objectives of this article are to review discrepancies in terminology in order to represent the piping processes better, to highlight past experimental work on the specific processes of soil pipeflow and internal erosion, and to assess the state-of-the-art modeling of pipeflow and internal erosion. The studies reviewed include those that examined the process of slope stability as affected by the clogging of soil pipes, the process of gullies forming due to mass failures caused by flow into discontinuous soil pipes, and the process of gully initiation by tunnel collapse due to pipes enlarging by internal erosion. In some of these studies, the soil pipes were simulated with perforated tubes placed in the soil, while in others the soil pipes were formed from the soil itself. Analytical solutions of the excess shear stress equation have been applied to experimental data of internal erosion of soil pipes to calculate critical shear stress and erodibility properties of soils. The most common numerical models for pipeflow have been based on Richards’ equation, with the soil pipe treated as a highly conductive porous medium instead of a void. Incorporating internal erosion into such models has proven complicated due to enlargement of the pipe with time, turbulent flow, and episodic clogging of soil pipes. These studies and modeling approaches are described, and gaps in our understanding of pipeflow and internal erosion processes and our ability to model these processes are identified, along with recommendations for future research.

Flow Induced Aerodynamic Noise Analysis of Perforated Tube Mufflers

AbstractDespite the analysis of muffler performance for many years, most works focus mainly on reducing inlet sound and fail to consider the flow effect. Most of their results correlate well with the experimental measurements. Subsequent works have considered the mean flow effect. Owing to Doppler's effect, transmission loss curve of the muffler will shift in its corresponding frequency. However, the correlation is worse than the experimental results since the flow induced noise does not include in the analysis. This work elucidates how flow induced noise affects muffler performance by analyzing a uniform flow that passes through perforated mufflers. The flow field is calculated with the CFD method, followed by evaluation of the aerodynamic noise based on the simulation results. Additionally, the procedure is simplified by computing and comparing only the total sound power induced by the flow in the muffler interior. Two muffler types, Helmholtz resonator and plug perforated tube muffler, are analyzed and discussed.

A study of deformation of a tube plate by means of holographic interferometry and the method of finite elements

Results from an experimental investigation of fields of elastic displacements of a complex construction by means of holographic interferometry are presented. A multiply perforated tube plate under complex attachment conditions and experiencing a uniformly distributed load is used as the construction. The experimental results obtained are compared to the data of a calculation of fields of elastic deflections performed by the method of finite elements.

Finite element analysis of transversal modes and acoustic attenuation characteristics of perforated tube silencers

Finite element analysis of transversal modes and acoustic attenuation characteristics of perforated tube silencers

A CFD study on a vertical chemical vapor deposition reactor for growing carbon nanofibers

A computational fluid dynamic (CFD) study has been carried out to simulate velocity, temperature, and concentration profiles in a vertical chemical vapor deposition (CVD) reactor used for growing carbon nanofibers (CNFs). CNFs were grown over activated carbon fibers (ACFs) wrapped over an especially designed perforated tube which was vertically mounted in the reactor. The numerical model analysis incorporated the conservation equations of momentum, energy, and species. Natural convection effects on the heat-transfer and the exothermic heat generation due to the decomposition of benzene were included. The model simulation results revealed that approximately uniform temperature and concentration profiles existed in the ACF-packed bed. In addition, multiple combinations of the heating length and the wall temperature of the reactor were possible to achieve the prescribed CVD temperature. Under the simulated CVD conditions, the present model predicted an average carbon deposition rate of 5×10−13kg/m2s, which corresponded to the yield of ∼0.005g of CNFs per g of ACFs. The simulation results of this study are important for the optimization of the CVD operating conditions to achieve a high and uniform CNF growth in the vertical reactor.

Transversal modes and acoustic attenuation characteristics of rectangular and oval silencers with perforated tube

As the analytical method is not suitable for the silencers with arbitrary cross-sectional shape, the finite element method is developed to calculate the transversal modes of rectangular and oval silencers with circular perforated tube, the corresponding finite element formulation is derived and the computational code is written. In order to validate the present finite element formulation and computational code, the transversal modal frequencies of circular concentric straight-through perforated tube silencer are evaluated analytically and compared with the finite element results, and good agreements between them are observed. Then, the finite element method is used to investigate the effects of hole diameter, porosity and tube offset on the transversal modes and acoustic attenuation characteristics of rectangular and oval silencers with circular perforated tube. The numerical results demonstrate that, smaller hole diameter or higher porosity leads to higher plane wave cut-off frequencies and better acoust...

The Potential of Temporary Immersion Bioreactors (TIBs) in Meeting Crop Production Demand in Nigeria

Micropropagation, popularly known for large-scale clonal propagation, is the first major and widely accepted practical application of plant biotechnology. The commercial utility of conventional micropropagation of important crop species is limited as a result of the large numbers needed annually to start up new farms in addition to high production costs. These result primarily from high labour cost, low multiplication rate or long duration of multiplication before plantlets are taken to the field, and poor survival rates resulting from contamination risks and during acclimatization. All of these constitute a major setback in the use of Micropropagation for scaling up of the several economic species for commercialization. Temporary Immersion Bioreactor system (TIBs) is a relatively recent micropropagation procedure that employs the use of automated gadgets to control rapid multiplication of plant cultures under adequate conditions. TIBs provide a more precise control of the adequate conditions (gaseous exchange, illumination etc.) required by plants for growth, development and survival than the conventional culture vessels. This bioreactor system incorporates a number of features specifically designed to simplify its operation and reduce production costs. The set-up consists of two vessels, one for the plantlets and the other one for the liquid culture media coupled together through a perforated rubber tubing that permits the flow of the liquid media from one vessel to the other. TIBs consist of three main phases: Multiplication, Elongation and Rooting phase. Plantlets propagated in TIBs have better performance than those propagated by conventional methods of micropropagation. This is as a result of a better handling of the in vitro atmosphere and the nutrition. TIBs provide a rapid and efficient plant propagation system for many agricultural and forestry species, utilizing liquid media to avoid intensive manual handling. In addition to diminishing production costs regarding labour force, Temporary Immersion Bioreactors save energy, augment micropropagation productivity and efficiency.

Fast multipole boundary element approaches for acoustic attenuation prediction of reactive silencers

Abstract The fast multipole boundary element method (FMBEM) is applied to predict the acoustic attenuation performance of reactive silencers. In order to overcome the difficulty of singular boundaries for the acoustic computation of reactive silencers with internal thin wall structure or/and perforated components, two approaches, the substructure FMBEM (Sub-FMBEM) and mixed-body FMBEM (MB-FMBEM) are proposed, and the theoretical foundations and numerical processes of the both approaches are introduced. The studies demonstrated that the ordering of column vectors and numbering of nodes in the Sub-FMBEM have great influence on the convergence of iteration, and the MB-FMBEM may reduce the number of elements and the computational complexity since it only needs to discretize one side boundary of the thin wall and perforated components and it is not necessary to create the interfaces. The Sub-FMBEM, MB-FMBEM and Sub-BEM are then employed to calculate the transmission loss of reactive silencers with thin wall components and perforated tubes, the computational accuracy and efficiency of the approaches are validated. The data of precomputing time and total iterative computational time demonstrated that, the computational efficiency of Sub-FMBEM will descend as the frequency arising, and the Sub-FMBEM may reveal higher computational efficiency than Sub-BEM only when the number of nodes is big enough.

Heavy metal fate in pilot-scale sludge drying reed beds under various design and operation conditions

Thirteen pilot-scale sludge drying reed bed (SDRB) units have been constructed and operated under various settings. The beds included a cobbles lower layer, where perforated PVC aeration tubes were placed, and two gravel layers on top. The setup included planted beds with common reeds and control units. Three sludge loading rates (SLR) were examined: 30, 60 and 75kgdm/m2/yr. Heavy metal (HM) accumulation in the residual sludge layer was negligible or low, and was found to increase with sludge layer depth. Plant uptake was low; the belowground biomass accumulated significantly more HMs compared to the aboveground biomass. Less than 16% of the influent HM left the bed through drainage. HM accumulation in the gravel layer was the major metal sink in the mass balance. On the whole, the HM content of the residual sludge was below the legal limits proposed by the EU for land application.

Effects of Aging Temperature on Moisture Absorption of Perforated GFRP

This paper examines the effects of aging on the flexural stiffness and bending loading capacity of a perforated glass fiber-reinforced epoxy composite subjected to combined moisture and elevated temperature. Specimens, in the configuration of one-quarter of a perforated GFRP tube, were aged in 60% humidity and temperatures of 40, 60, and 80°C, respectively. Moisture absorptions of the specimens were measured during the aging process, and bending tests were conducted on the specimens after aging. The SEM images were also captured to further examine the effects of the moisture absorption on the aged specimens. The results indicated that the increase in the aging temperature reduced the diffusion coefficient, thus inducing more moisture absorption by the composite and in turn causing more reduction in composite’s flexural stiffness and bending capacity. Moreover, the ability of Fick’s equation for predicting the moisture absorption rate in such perforated thin-walled composite configuration at various moisture contents and temperatures was also assessed. A semiempirical equation was developed and proposed by which the reduction of the stiffness in the perforated aged GFRP structures could be predicted.

Nano-Coating Process for Si [1 0 0] Wafer Using Atmospheric Pressure Plasma Jet (APPJ)

Three-electrode plasma jet system consisting of a perforated dielectric tube with two outer and one floating inner electrodes was developed and employed for nano-coating processes of Si [1 0 0] wafer. Lowered gas breakdown voltage, increasing plasma density and increased discharge current were achieved by using the floating inner electrode. The low temperature (Nonthermal) Atmospheric Pressure Plasma protective coating technique using precursor-containing gases (Ar, O2 and OMCTS mixture) which injected into Plasma Jet (APPJ), there are several techniques are introduced here to avoid substrate damage including increasing plasma density without increasing the kinetic energy of the ion bombardment. Furthermore some few precautions are given here to insure good media for silicon wafer prepared for coating.

Optimal Design of Side-Inlet/Side-Outlet Expansion Mufflers with Open-Ended Perforated Tubes Using Simulated Annealing

ABSTRACTResearch on new techniques of multi-chamber mufflers equipped with a side inlet and internal nonperforated intruding tubes has been discussed in recent literature; however, the research work of multichamber mufflers in conjunction with side inlet and open-ended perforated intruding tubes which may efficiently increase the acoustical performance has been neglected. Therefore, the main purpose of this paper is to optimize the best design shape of multi-chamber side mufflers with open-ended perforated intruding tubes within a limited space.In this paper, the four-pole system matrix in evaluating the acoustic performance is also deduced in conjunction with a simulated algorithm (SA). Results reveal that the maximum sound transmission loss (STL) is precisely located at the desired target tone. In addition, the acoustical performance of mufflers conjugated with perforated intruding tubes is superior to those equipped with non-perforated tubes. Additionally, the noise reduction ability for a three-chamber side muffler with a non-perforated intruding tube and a two-chamber side muffler with perforated intruding tubes are equivalent. Moreover, mufflers with more chambers will increase the acoustic performance for both pure tone and broadband noise.

Effect of various design and operation parameters on performance of pilot-scale Sludge Drying Reed Beds

Thirteen pilot-scale Sludge Drying Reed Bed units have been constructed and operated under various design and operational characteristics. All the beds included a cobbles bottom layer, where perforated PVC aeration tubes were placed. One bed did not contain aeration tubes. Two gravel layers were placed above the cobbles layer. The setup included planted beds with common reeds and control units. Three sludge loading rates were examined: 30, 60 and 75 kg dm/m 2/yr. The dewatering efficiency of the planted units exceeded 95% volume reduction. The final dry matter content varied between 50 and 64%, depending on the applied SLR. Mineralization of the residual sludge also took place. VS content of the planted units decreased up to 20%, while nutrient concentration was also reduced. The presence of reeds, aeration tubes and a fine-grained material improved the system efficiency, while the material composition did not have any effect on efficiency. Moreover, the units were able to treat sludge with high concentration of Cr.

Response of perforated composite tubes subjected to axial compressive loading

Perforated and slotted tubes are widely used as liners in oil and gas industry to facilitate the collection of products from reservoirs, and prevent sand migration to wellbore, which in return could cause product contamination and affect functionality of the pumps. The objective of this research is to establish the critical axial load of perforated E-glass/epoxy tubes using numerical and experimental methods. Firstly, in an experimental attempt, a total of six sets of composite tubes (three sets with perforations and three sets of intact (non perforated) tubes), having two different thicknesses and diameters, were fabricated and tested under axial compression. The reduction in the critical load and axial stiffness of the composite tubes was investigated experimentally. Secondly, a comprehensive numerical investigation was carried out, using the finite element method (FEM), to simulate the instability response of the intact and perforated composite tubes under compressive axial loading. The effect of various parameters such as the tube diameter, size, number of perforation and wall thickness were investigated in the current research. Good correlation is obtained between the experimental and numerical results. According to the results, the intact and perforated tubes showed similar instability mode shapes under the axial loading. However, the critical load and global stiffness of the perforated tubes were considerably reduced.

SOIL OXYGENATION EFFECTS ON GROWTH, YIELD AND NUTRITION OF ORGANIC GREENHOUSE TOMATO CROPS

Soil oxygen deficiency (hypoxia) reduces respiration, mineral uptake and water movement in roots, and may thus have a negative impact on plant growth and productivity. The supply of air or oxygen to the rhizosphere usually improves crop performance under anoxic/hypoxic soil conditions. However, little is known about the effect of O2 enrichment of the irrigation water or soil on organic greenhouse crops. The objective of this study was to determine the effect of soil oxygenation on soil biological activity, plant growth and development, yield and fruit quality. Seedlings of Lycopersicon esculentum (‘Macarena’ grafted on ‘Beaufort’) were transplanted into a loamy soil and grown in a greenhouse from February to October (oxygenated vs. control plots; four complete blocks). In 2008, O2 enrichment was provided by the irrigation water using pure O2 gas and venturi injectors (mean water O2 ~16 ppm), whereas in 2009 pure O2 was released from a network of small perforated (0.5 mm diameter holes) tubes installed at 25-cm depth into the soil (mean soil O2 ~25%). Soil surface CO2 flux was measured three times/year to determine biological activity. Growth parameters, yield and fruit quality were measured weekly. Soil and leaf mineral content were determined monthly. There was no difference in marketable yield between O2-enriched and control plots in 2008 but increased production (~2 kg m-2, P=0.108) under soil O2 enrichment in 2009. Soil CO2 fluxes were also higher in O2-enriched plots but on three sampling dates only. In general, no significant differences were observed in plant growth parameters or fruit quality. Leaf Mg and Fe levels and several soil nutrients (NO3, NH4, P and K) were significantly higher in O2-enriched plots. Long-term effects of soil O2 enrichment should be examined in different types of organically cultivated soils to conclude on any significant beneficial effect on soil biological activity and crop productivity.