Multiple Orifice Research Articles

Performance Assessment of Single and Multiple Jet Impingement Configurations in a Refrigeration-Based Compact Heat Sink for Electronics Cooling

The performance of a novel impinging two-phase jet heat sink operating with single and multiple jets is presented and the influence of the following parameters is quantified: (i) thermal load applied on the heat sink and (ii) geometrical arrangement of the orifices (jets). The heat sink is part of a vapor compression cooling system equipped with an R-134a small-scale oil-free linear motor compressor. The evaporator and the expansion device are integrated into a single cooling unit. The expansion device can be a single orifice or an array of orifices responsible for the generation of two-phase jet(s) impinging on a surface where a concentrated heat load is applied. The analysis is based on the thermodynamic performance and steady-state heat transfer parameters associated with the impinging jet(s) for single and multiple orifice tests. The two-phase jet heat sink was capable of dissipating cooling loads of up to 160 W and 200 W from a 6.36 cm2 surface for single and multiple orifice configurations, respectively. For these cases, the temperature of the impingement surface was kept below 40 °C and the average heat transfer coefficient reached values between 14,000 and 16,000 W/(m2 K).

Decolourization of Rhodamine B: A swirling jet-induced cavitation combined with NaOCl

A hydrodynamic cavitation reactor (Ecowirl) based on swirling jet-induced cavitation has been used in order to allow the degradation of a waste dye aqueous solution (Rhodamine B, RhB). Cavitation generated by Ecowirl reactor was directly compared with cavitation generated by using multiple hole orifice plates. The effects of operating conditions and parameters such as pressure, pH of dye solution, initial concentration of RhB and geometry of the cavitating devices on the degradation rate of RhB were discussed. In similar operative conditions, higher extents of degradation (ED) were obtained using Ecowirl reactor rather than orifice plate. An increase in the ED from 8.6% to 14.7% was observed moving from hole orifice plates to Ecowirl reactor. Intensification in ED of RhB by using hydrodynamic cavitation in presence of NaOCl as additive has been studied. It was found that the decolourization was most efficient for the combination of hydrodynamic cavitation and chemical oxidation as compared to chemical oxidation and hydrodynamic cavitation alone. The value of ED of 83.4% was reached in 37min using Ecowirl combined with NaOCl (4.0mgL−1) as compared to the 100min needed by only mixing NaOCl at the same concentration. At last, the energetic consumptions of the cavitation devices have been evaluated. Increasing the ED and reducing the treatment time, Ecowirl reactor resulted to be more energy efficient as compared to hole orifice plates, Venturi and other swirling jet-induced cavitation devices, as reported in literature.

Development and evaluation of a functional bioreactor for CO fermentation into ethanol

In a conventional syngas fermentation process, gas was released into the fermentation broth through a single orifice or multiple orifices, except the hollow fiber membrane reactor. Consequently, a simplified bioreactor has been developed employing an innovative gas supply and effluent extraction systems. A continuous stirred tank bioreactor (CSTBR) has been developed by incorporating an innovative gas supply and effluent extraction system to ferment syngas into ethanol. The working volume of the bioreactor was controlled to 2 L. The CO gas was fermented in the developed bioreactor by using a microorganism (Clostridium ljungdahlii) with different gas (5–15 mL/min), media, and effluent flow rates (0.25–0.75 mL/min) and stirrer speed (300–500 rpm). Gas was diffused into the fermenting broth through an aqueous aeration tube commonly used in the small household aquarium, placed at the bottom layer throughout the periphery. The effluent was extracted from the top layer of the broth by using a membrane separator. Ethanol and acetic acid concentrations were varied from 0.17–1.17 and 8.50–23.68 g/L-effluent, respectively. It seems that the performance of CSTBR can be enhanced with an innovative gas supply system, which may reduce the gas bubble size and result in higher lateral velocity at the releasing point, especially, throughout the periphery instead of the center of the reactor through a single or multiple orifice.

원자로 압력 및 체적제어계통의 다단 오리피스 설계

다공 및 다단오리피스열을 해석할 수 컴퓨터코드를 사용하여 원자력발전소 내 공급 및 배출장치의 수축오리피스를 설계하였다. 원래 단공 오리피스가 설치되었으나 다공 오리피스 설치가 필요하여 설계 변경되었다. 오리피스 사이 거리는 충분한 압력회복거리로 유지되었다. 최소 정압은 공동현상 방지를 위하여 그 온도에 상응하는 증기압 이하로 유지되도록 설계하였다. 오리피스 설치 배관의 직경은 운전시 강성을 유지할 수 있도록 원래 크기보다 증가시켰다. Restriction orifices in the feed and bleed circuit of nuclear power plant are designed using computer program capable of handling multiple hole cascade orifice assembly. Single hole stages of orifice assembly are alternated with multihole stages where necessary. The distance between stages is such that it allows full pressure recovery. The minimum static pressure is higher than vapor pressure at the operating temperature so that cavitation does not occur. Piping sizes are reviewed and increased if necessary to improve rigidity.

Tamanho de bolhas de ar formadas por difusores não porosos na água

Neste estudo foram realizados experimentos para investigar o tamanho de bolhas de ar formadas a partir de difusores não porosos em um tanque de água. O tamanho das bolhas individuais e o diâmetro de Sauter foram avaliados usando uma técnica de processamento de imagens. Os resultados confirmam que a vazão de ar e o diâmetro do orifício são parâmetros importantes que controlam a distribuição do tamanho das bolhas e o diâmetro de Sauter. Análise dimensional é realizada para fornecer uma relação adimensional geral para predição do diâmetro de Sauter (usando uma escala de comprimento adequada, baseada na vazão de ar) e o número de Reynolds na saída do orifício. Essa relação apresenta bom ajuste aos dados experimentais obtidos neste estudo e a partir de investigações anteriores disponíveis na literatura, incluindo também experimentos com múltiplos orifícios. Finalmente, são apresentadas aplicações potenciais da relação adimensional obtida.

Numerical Investigation on Microelectronic Chip Cooling Using Multiple Orifice Synthetic Jet Actuator Based on Theory Field Synergism

Synthetic jet is applied to the field of heat and mass transfer, because the periodical suck and blow enhances forced convection heat transfer. A multiple orifice synthetic jet actuator (SJA) is designed for the cooling of microelectronic chips. By using fin, it can achieve higher effectiveness of heat transfer with a combination of active and passive scheme in heat dissipation. Numerical simulation of the flow field of the multiple orifice SJA is performed to analyze the mechanism of the heat dissipation. Based on the above work, numerical simulations presenting the effects of heat dissipation with different flat-to-orifice distances are performed in this study. The theory Field Synergism of the optimization of convection heat transfer is introduced to evaluate the effects of the parameters on heat transfer by comparing the magnitude of the integral value. The results verify that the larger the integral value is, the higher the heat transfer coefficient is. And there is an optimum impinging distance at which the synergy degree between velocity field and temperature gradient field reaches its peak and the heat transfer coefficient is the highest.

Comparative Study of Mass Transfer and Bubble Hydrodynamic Parameters in Bubble Column Reactor: Physical Configurations and Operating Conditions

In this paper, effects of physical configurations and operating conditions on bubble column performance were analyzed in terms of bubble hydrodynamic and mass transfer parameters. Bubble column with 3 different dimensions and 7 gas diffusers (single / multiple orifice and rigid / flexible orifice) were applied. High speed camera and image analysis program were used for analyzing the bubble hydrodynamic parameters. The local liquid-side mass transfer coefficient (kL) was estimated from the volumetric mass transfer coefficient (kLa) and the interfacial area (a), which was deduced from the bubble diameter (DB) and the terminal bubble rising velocity (UB). The result showed that the values of kLa and a increased with the superficial gas velocity (Vg) and the size of bubble column. Influences of gas diffuser physical property (orifice size, thickness and orifice number) can be proven on the generated bubble size and the mass transfer performance in bubble column. Concerning the variation of kL coefficients with bubble size, 3 zones (Zone A, B and C) can be observed. For Zone A and Zone C, a good agreement between the experimental and the predicted KL coefficients was obtained (average difference of 짹 15%), whereas the inaccuracy result (of 짹 40%) was found in Zone B. To enhance the high kLa coefficient and absorption efficiency in bubble column, it was unnecessary to generate numerous fine bubbles at high superficial gas velocity since it causes high power consumption with the great decrease of kL coefficients.

Effect of Injector Nozzle Design on Spray Characteristics for Hydrogen Direct Injection Engine Conditions

Hydrogen has a unique flammability property compared to other fuels. Previous researches proved that direct injection is the most suitable method for this particular fuel. This research aims to study the effect of injector nozzle geometry on mixture and internal combustion efficiency in four stroke automotive engine which operates using hydrogen fuel. The research will concentrate on two aspects, namely the inflow and outflow profile of the injector nozzle. For each flow profile, the effect of geometrical design of the nozzle on the parameter such as flow velocity, fuel penetration distance, average mass fuel consumption and diffusion will be studied in detail. In this study, numerical simulation analysis was done by using the computing fluid dynamics (CFD) software, Star-CCM+. Models comprise of multiple orifice nozzle geometry with single angle orifice and double angle orifice was developed with CAD software. A suitable design for a better mixing nozzle would then be determined. Nozzle which possesses a high number of orifice and a smaller diameter will result in a higher flow velocity in the cavity nozzle channel. Geometry of nozzle with different angle of orifice was found to be the most suitable due to the low flow penetration distance and fuel consumption as well as combustion enhancement by the diffusion rate.

Heat Transfer and Flow Structure Evaluation of a Synthetic Jet Emanating from a Planar Heat Sink

Direct impinging synthetic jets are a proven method for heat transfer enhancement, and have been subject to extensive research. However, despite the vast amount of research into direct synthetic jet impingement, there has been little research investigating the effects of a synthetic jet emanating from a heated surface, this forms the basis of the current research investigation. Both single and multiple orifices are integrated into a planar heat sink forming a synthetic jet, thus allowing the heat transfer enhancement and flow structures to be assessed. The heat transfer analysis highlighted that the multiple orifice synthetic jet resulted in the greatest heat transfer enhancements. The flow structures responsible for these enhancements were identified using a combination of flow visualisation, thermal imaging and thermal boundary layer analysis. The flow structure analysis identified that the synthetic jets decreased the thermal boundary layer thickness resulting in a more effective convective heat transfer process. Flow visualisation revealed entrainment of local air adjacent to the heated surface; this occurred from vortex roll-up at the surface of the heat sink and from the highly sheared jet flow. Furthermore, a secondary entrainment was identified which created a surface impingement effect. It is proposed that all three flow features enhance the heat transfer characteristics of the system.

A high performance magnetorheological valve with a meandering flow path

The huge developments in the field of magnetorheological (MR) fluid-based devices will have a great influence on the future of mechatronic applications due to the ease of interfacing between electronic controls and the mechanical components that they provide. Among various MR fluid-based devices, an MR valve would be particularly significant for the development of other devices, if it could be successfully achieved. One of the most challenging obstacles to MR valve development is the difficulty of achieving device miniaturization while, at the same time, improving the achievable performance. This study demonstrates a novel design for an MR valve, using the meandering flow path approach in order to increase the effective area so that the MR fluid can be regulated within a small-sized valve. The meandering flow path is formed by combining multiple annular, radial and orifice flow channels. In order to analyze the valve performance, a mathematical model of the proposed MR valve is derived and combined with numerical simulation using the finite element method, with the intention of predicting the achievable pressure drop that can be generated by the valve. The predicted MR valve performances are then experimentally evaluated using an oscillation-disturbed bypass hydraulic cylinder. The simulation results show that the proposed MR valve design could yield substantial pressure drop improvement, which is confirmed by the experiment.

Multiple orifices in customized microsystem high-pressure emulsification: The impact of design and counter pressure on homogenization efficiency

Abstract A continuous production of nanoemulsions (or solid lipid nanoparticles) via a single passage through a homogenization device is a challenging, yet essential prerequisite of upstream or downstream processes in an integrated overall microsystem. Multiple orifice microsystems with consecutive orifice arrangements were identified as especially efficient tools for this purpose. Design, process, and formulation parameters were studied to evaluate their influence on the process efficiency and the underlying mechanisms affecting the droplet breakup and droplet stabilization efficiency. The application of multiple orifices in one microsystem reduces the coalescence of broken up droplets due to the establishment of a turbulent mixing zone. Therein, the frequency of droplet collision is elevated and, in turn, their collision time is shorter than the coalescence time. Thus, the droplets are fluid dynamically stabilized against coalescence. Double orifices are found more efficient than triple orifices because the breakup is superior due to higher energy density. The combination of differently wide orifices as well as the orifice order and the inter-orifice distances also influence the homogenization result. The combination of orifices must be selected to yield a counter pressure in the range of Thoma numbers between 0.1 and 0.4, as described for common two-stage homogenizers. The variation of formulation parameters displayed that the improved double orifice efficiently produces small particle sizes virtually independent of the emulsifier properties and the viscosity of the continuous phase. In conclusion, a versatile microsystem design has been developed and characterized for a highly efficient processing of a broad range of formulations and to suit a complex process chain by consuming only a minimum of pressure drop (e.g. 1000 bar).

Evaluation of a solid stream radial nozzle on fixed-wing aircraft, for penetration of spray within a soybean canopy

Abstract Experiments were conducted to evaluate the Accu-Flo multiple orifice nozzle for penetration of spray into a soybean (Glycine max L.) canopy by comparing results to those from a popular straight stream nozzle and rotary atomizer. A mixture of water + Induce® adjuvant was applied at three different spray release heights in a random sequence, using an Air Tractor 402-B agricultural aircraft. Sampler stands were placed at twenty-four locations in the field. Water sensitive paper (WSP) cards were clipped onto rigid stands just above the canopy and 30 cm off the ground within the canopy. Weather data were recorded using two different stations on-site. Wind was predominantly from the west and parallel to the direction of the spray runs. The spray delivery systems compared were the Accu-Flo nozzles, (64 needle 0.020 opening), CP®-09 straight stream with 5 degree deflection, and Micronair® AU5000 atomisers (14 mesh screen) at a low volume spray rate of 18.7 l/ha. A total of 54 spray runs were made over three days, and heights were varied at 3.7 m, 4.9 m and 6.1 m. Water sensitive papers were scanned and analysed for coverage per unit card area using an image analysis system. Altitude and [Nozzle X Altitude] interaction were significant effects on coverage at the 0.01 and 0.07 significance levels, respectively, for the top cards. Nozzle type was not a significant effect on coverage for the top cards, but was significant at the 0.01 level for the bottom cards. Altitude alone had no obvious effect on coverage for the bottom cards, although it had an effect for the top cards. The highest percentage area of spray coverage was observed from the Accu-Flo nozzles, especially for the bottom cards. Average spray coverage from the Accu-Flo nozzles was 1.7 times higher than coverage from the CP® nozzles or Micronair® atomisers in the lower portion of the canopy.

The Influence of Slenderness Ratios of Multi-Hole Ceramic Filters from S<sub>F</sub> - 1.67 to S<sub>F </sub>- 8.36 of Filter Surface on Efficiency of Liquid Steel Refining from Non-Metallic Phase

We propose in this publication the introduction of new, additional definition describing the multiple orifice ceramic filters used in research works on the liquid steel filtrations, calling this the filter slenderness ratio. In order to confirm the theoretical assumptions we have performed a series of the laboratory scale experiments (for the filter slenderness ratio SF - 1.67 to SF - 8.36). The influence of the filter slenderness on the filtration process efficiency has been determined through variations in quantities and surface shares of the non-metallic phase in the filtrated steel in relation to the non-filtered steel. We present also the results of researches on the separating surfaces between the liquid steel and the ceramic filter material, which in form of photos and scanning microscope microanalyses are put together in the publication.

The Slenderness Ratio of the Filter Used in the Process of Liquid Steel Filtration as the Additional Parameter of the Filter Form

AbstractWe propose in this publication the introduction of new, additional definition describing the multiple orifice ceramic filters used in research works on the liquid steel filtrations, calling this the filter slenderness ratio. In order to confirm the theoretical assumptions we have performed a series of the laboratory scale experiments (for the filter slenderness ratio SF1 λ = 1.67 and SF2 λ = 3.34). The influence of the filter slenderness on the filtration process efficiency has been determined through variations in quantities and surface shares of the non‐metallic inclusions in the filtrated steel in relation to the non‐filtered steel. We present also the results of researches on the separating surfaces between the liquid steel and the ceramic filter material, which in form of photos and scanning microscope microanalyses are put together in the publication.

The influence of customized geometries and process parameters on nanoemulsion and solid lipid nanoparticle production in microsystems

In many fields of research and technology, nanodisperse formulations are applied. Especially in pharmaceutical applications, it is necessary to facilitate the processing of small educt batches for formulation screening of new active pharmaceutical ingredient in high quality. In this study, the design of microsystems for high-pressure homogenization is systematically studied and variations of design parameters are evaluated. The designs primarily produced in silicon are successfully transferred to stainless steel to facilitate higher pressure drops over the homogenizing structure at elevated temperature required for solid lipid nanoparticle (SLN) processing. Different groups of geometric principles are applied and can be ranked by droplet breakup efficiency: straight channel<z-channel<orifice∼y-channel. Changes within a geometric principle alter the droplet breakup efficiency as well. Conclusively, nanoemulsion (NE) and SLN can be produced in the customized microchannels presented. Especially multiple orifice systems and y-channels with rounded inlet structures prove most efficient.

Metal and Metalloid Contaminants in Atmospheric Aerosols from Mining Operations

Mining operations are potential sources of airborne metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, with potential deleterious effects on human health and ecology. Fine particulates such as those resulting from smelting operations may disperse more readily into the environment than coarser tailings dust. Fine particles also penetrate more deeply into the human respiratory system, and may become more bioavailable due to their high specific surface area. In this work, we report the size-fractionated chemical characterization of atmospheric aerosols sampled over a period of a year near an active mining and smelting site in Arizona. Aerosols were characterized with a 10-stage (0.054 to 18 μm aerodynamic diameter) multiple orifice uniform deposit impactor (MOUDI), a scanning mobility particle sizer (SMPS), and a total suspended particulate (TSP) collector. The MOUDI results show that arsenic and lead concentrations follow a bimodal distribution, with maxima centered at approximately 0.3 and 7.0 μm diameter. We hypothesize that the sub-micron arsenic and lead are the product of condensation and coagulation of smelting vapors. In the coarse size, contaminants are thought to originate as aeolian dust from mine tailings and other sources. Observation of ultrafine particle number concentration (SMPS) show the highest readings when the wind comes from the general direction of the smelting operations site.

Multiple orifice synthetic jet for improvement in impingement heat transfer

Synthetic jet is potentially useful for cooling of electronic components and its utility has been investigated in previous studies. Synthetic jet will become further attractive if additional cooling can be obtained without a corresponding increase in the input power. In this context, we explore the use of multiple orifice single-cavity synthetic jet employed in direct impingement mode of cooling. Experiments are conducted for different configurations with a center orifice surrounded by multiple satellite orifices. The Reynolds number is in the range of 1000–2600 while the normalized axial distance is varied in the range of 1–30 in this study. The maximum heat transfer coefficient with multiple orifice synthetic jet is approximately 12 times that of the natural heat transfer coefficient and up to 30% more as compared to that obtained with a conventional single orifice jet. Interestingly, the average Nusselt number gets maximized at two axial distances-the two peaks can be of comparable magnitude. The appearance, location and magnitude of the two peaks depend on the number of satellite orifices and the pitch circle radius on which the satellite holes lie. It is proposed that a transition in flow behavior from multiple-jet to a combined-jet occurs, which leads to the appearance of this additional peak. The additional peak (at the smaller axial distance) can be utilized in the design of cooling solutions for compact devices. The input power reduces slightly in the multi-orifice case with respect to the conventional design. The average velocity at the surface is also obtained with the help of hot-wire anemometry. The use of multiple orifice synthetic jet does not appear to have been explored earlier and the results are expected to be useful in several practical applications.

Calibrating the multiple orifice mathematical model using physical scale model foam at low Reynolds number

Recently, gelcast ceramic foams are being considered as potential diesel particulate filter substrates. Consequently, a mathematical model known as the Multiple Orifice Mathematical (MOM) model for the study of fluid flow and the determination of pressure gradients across the foam filters was developed and calibrated by some researchers. However, there was need to establish the model application on a wider range of pore sizes of the foam filters. Hence, this work is to establish the dynamic similarity of the physical scale model used for the calibration and the ceramic foams. Following the conceptual model employed in the development of the MOM model, generic physical scale foam models and a fluid flow rig was fabricated. The pressure drops across the generic physical model foam obtained from experiments over different ranges of low Reynolds number were graph-fitted against the MOM model to determine the kinetic correction factors. The values for the kinetic correction coefficient determined from the generic physical model at low Reynolds number is within the range obtained by other researchers in the calibration of the MOM model, which implies that the MOM model can be applied to a wide range of pore sizes found in gelcast ceramic foam filters. Key words: Diesel particulate trap, gelcast ceramic foam, kinetic correction coefficient, generic foams, foam filters, pressure gradients.

Two-phase flow characteristics in multiple orifice valves

This work presents an experimental investigation on the characteristics of two-phase flow through multiple orifice valve (MOV), including frictional pressure drop and void fraction. Experiments were carried out using an MOV with three different sets of discs with throat thickness-diameter ratios ( s/ d) of 1.41, 1.66 and 2.21. Tests were run with air and water flow rates ranging between 1.0 and 3.0 m 3/h, respectively. The two-phase flow patterns established for the experiment were bubbly and slug. Two-phase frictional multipliers, frictional pressure drop and void fraction were analyzed. The determined two-phase multipliers were compared against existing correlations for gas–liquid flows. None of the correlations tested proved capable of predicting the experimental results. The large discrepancy between predicted and measured values points at the role played by valve throat geometry and thickness-diameter ratio in the hydrodynamics of two-phase flow through MOVs. A modification to the constants in the two-phase multiplier equation used for pipe flow fitted the experimental data. A comparison between computed frictional pressure drop, calculated with the modified two-phase multiplier equation and measured pressure drop yielded better agreement, with less than 20% error.

NOTES Performed Using Multiple Ports of Entry: Current Experience and Potential Implications for Urologic Applications

An isolated transgastric port raises serious limitations in performing natural orifice translumenal endoscopic surgery (NOTES) complex procedures in the urology field. In an attempt to overcome these limitations, several solutions has been advanced, such as the hybrid approach (adding a single abdominal port access) or the pure NOTES combined approach (joining multiple natural orifice ports). To review the current state of experimental and clinical results of multiple ports in NOTES, a literature search of PubMed was performed, seeking publications from January 2002 to 2008 on NOTES. In addition, we looked at pertinent abstracts of annual meetings of the American Urological Association, the European Association of Urology, and the World Congress of Endourology from 2007. Multiple ports of entry seem to be necessary, mainly for moderately complex procedures. Thus, we could find studies using the hybrid approach (combination of transgastric or transvaginal access with a single transabdominal port), or using the pure NOTES combined approach (transgastric and transvesical, transvaginal and transcolonic, or transgastric and transvaginal). There is still limited experience in humans using these approaches, and no comparative studies exist to date. It is predictable that for moderately complex procedures, we will need multiple ports, so the transvaginal-transabdominal (hybrid) approach is the most appealing, whereas in a pure NOTES perspective, the transgastric-transvesical approach seems to be the preferred approach. We are waiting for new equipment and instruments that are more appropriate for these novel techniques.