Outlet Side Research Articles

INVESTIGATION OF MODE SCATTERING BY HARD STRIPS IN LINED DUCTS USING COLLOCATION

When mounting acoustic liners inside the inlet duct of aircraft jet engines, hard strips exist in-between liner sections in order to hold them in place. It has been generally acknowledged, from experiments, that the existence of hard strips inside lined ducts affects the attenuation behaviour of the duct. The acoustic energy is scattered and rearranged among different modes so that it might be transferred into modes which are less attenuated by the liner. Moreover, cut-off modes may scatter into cut-on modes. In this paper, flow is included in the locally reacting liner case, which is more interesting to the aeronautics applications. Moreover, the duct is made finite and connected to two semi-infinite hard inlet and outlet ducts. By using mode matching, it is possible to input any mode at the inlet side and to study the modes on the outlet side. Comparisons are made between different hard strip cases and the splice-less liner case.

Study of orange peels dryings kinetics and development of a solar dryer by forced convection

The solar drier project aims at using solar energy as heat source, frequent in the area, for the drying of perishable products. Solar drier does not degrade any more the dried products with the manner of the products dried at the natural sun. The drying unit is composed mainly of a solar air collector and a drying chamber. The transformation of the solar radiation into heat is done thanks to the solar collector whose effectiveness is increased by the addition of suitable baffles in the mobile air vein. The efficiency of the collector reaches then 80%. The hot air on the outlet side of the collector arrives in the drying chamber where the heat transfer with the product to be dried is done by convection. The drying kinetics study shows that in addition to the dependence of the temperature and air velocity of drying, the rate of drying also depends on sectioning on the product to dry, and mainly, of the product surface in contact with the drying air. Thus, the moisture content in wet basis is reduced from 76 to 13% in one day. Then, we obtains dried products in a healthy way, and the so frequent sand wind in the area does not degrade any more the dried products quality at the manner of the products dried with the free air. The total efficiency of the drier reached 28%.

Modeling runoff dynamics from zero-order basins: implications for hydrological pathways

Although zero-order basins (geomorphic hollows) are important components of headwater catchments, their hydrologic regime has not been thoroughly investigated. A multi-tank model approach is used to simulate flow from zero-order basins in Hitachi Ohta Experimental Watershed, Japan, and simulations are compared with six months of wet season flows. A three-tank model accurately simulated runoff for the 6-month period from basin (FA) with two zero-order basins and deep soils, whereas a two-tank model performed satisfactorily in a zero-order basin with shallower soils (ZB). Characteristics of flow paths were evaluated and the concept of “threshold response” was assessed in simulations. In FA, preferential flow from the upper outlet of Tank 1 only occurred during the two largest storms; no overland flow was simulated. Less rapid subsurface flow emitted from the side outlet of Tank 2 during large and several moderate-size storms. During small storms, no overland, preferential, or subsurface flows occurred. Water depth in Tank 3, which indicates shallow groundwater storage in FA, is highly correlated with 30-day antecedent rainfall. The concept of “threshold response” is evidenced by intermittent quick and moderate flows from Tanks 1 and 2, respectively.

Alloying Effects on the Hydrogen Diffusivity during Hydrogen Permeation through Nb-Based Hydrogen Permeable Membranes

The hydrogen solubility and the hydrogen permeability have been measured for Nb-based alloys in order to investigate the alloying effects on the hydrogen diffusivity during hydrogen permeation. The hydrogen diffusion coefficient during hydrogen permeation is estimated from a linear relationship between the normalized hydrogen flux, , and the difference of hydrogen concentration, C, between the inlet and the outlet sides of the membrane. It is found that the hydrogen diffusion coefficient during the hydrogen permeation is increased by alloying ruthenium or tungsten into niobium. On the other hand, the activation energy for hydrogen diffusion in pure niobium under the practical permeation condition is much higher than the reported values measured for dilute hydrogen solid solutions. It is interesting that the activation energy for hydrogen diffusion decreases by the addition of ruthenium or tungsten into niobium.

Water modeling of molten steel flow in a multi-strand tundish with gas blowing

Fluid flow characteristics in a four-strand tundish with gas blowing were studied by water modeling experiments. It is found that gas blowing can greatly improve the flow characteristics in the tundish with a turbulence inhibitor. It dramatically increases the peak concentration time, and greatly decreases the dead volume, and reduces the minimum residence time. The gas blowing location, gas flow rate, and porous plug area greatly influence the flow characteristics in the tundish; the gas blowing location near the baffle, smaller gas flow rate, and smaller porous plug area are better for improving the fluid flow characteristics. Using gas blowing can reduce the difference of flows at the middle outlets and side outlets for the multi-strand tundish. Bubbles produced by gas blowing can absorb small inclusions and provide the condition for inclusion collision and aggregation. Therefore, introducing gas blowing into a tundish and combining the turbulence inhibitor can improve inclusion floating and removal, and the cleanness of molten steel can be advanced.

Deformability based cell margination—A simple microfluidic design for malaria-infected erythrocyte separation

In blood vessels with luminal diameter less than 300 µm, red blood cells (RBCs) which are smaller in size and more deformable than leukocytes, migrate to the axial centre of the vessel due to flow velocity gradient within the vessels. This phenomenon displaces the leukocytes to the vessel wall and is aptly termed as margination. Here, we demonstrate using microfluidics that stiffer malaria-infected RBCs (iRBCs) behave similar to leukocytes and undergo margination towards the sidewalls. This provides better understanding of the hemodynamic effects of iRBCs in microcirculation and its contribution to pathophysiological outcome relating to cytoadherence to endothelium. In this work, cell margination is mimicked for the separation of iRBCs from whole blood based on their reduced deformability. The malaria infected sample was tested in a simple long straight channel microfluidic device fabricated in polydimethylsiloxane. In this microchannel, cell margination was directed along the channel width with the iRBCs aligning near each sidewall and then subsequently removed using a 3-outlet system, thus achieving separation. Tests were conducted using ring stage and late trophozoite/schizont stage iRBCs. Device performance was quantified by analyzing the distribution of these iRBCs across the microchannel width at the outlet and also conducting flow cytometry analysis. Results indicate recovery of approximately 75% for early stage iRBCs and >90% for late stage iRBCs at the side outlets. The simple and passive system operation makes this technique ideal for on-site iRBCs enrichment in resource-limited settings, and can be applied to other blood cell diseases, e.g. sickle cell anemia and leukemia, characterized by changes in cell stiffness.

Alloying effects of Ru and W on hydrogen diffusivity during hydrogen permeation through Nb-based hydrogen permeable membranes

The hydrogen permeability have been measured for pure niobium and Nb-5 mol%X ( X = Ru and W) alloys in order to investigate the alloying effects of ruthenium and tungsten on the hydrogen diffusivity during hydrogen permeation. The hydrogen diffusion coefficient during hydrogen permeation is estimated from a linear relationship between the normalized hydrogen flux, J· d, and the difference of hydrogen concentration, Δ C, between the inlet and the outlet sides of the membrane. It is found that the addition of ruthenium or tungsten into niobium increases the hydrogen diffusion coefficient during the hydrogen permeation. On the other hand, the activation energy for hydrogen diffusion in pure niobium under the practical permeation condition is much higher than the reported values measured for dilute hydrogen solid solutions. It is interesting that the activation energy for hydrogen diffusion is decreased by alloying of ruthenium or tungsten into niobium.

Microfabricated evanescent-light funnel with high-intensity cold atom flux

We process a silicon-on-insulator substrate into a funnel with a 25-μm-side square-shaped outlet by photolithography and anisotropic chemical etching. The funnel is utilized to form a cold atomic beam by means of reflection and cooling on repulsive evanescent light. Monte Carlo simulations show that the flux intensity of emitted cold Rb atoms reaches 10 12 cm −2 s −1. The mean horizontal velocity is estimated to be below 10 cm/s, while the mean vertical velocity decreases in proportion to the outlet side. The evanescent-light funnel can be developed to concentrate 80% of Rb atoms falling from a standard magneto-optical trap.

Experimental Study of a New Hydrocyclone for Multi-Density Particles Separation

A new structure of hydrocyclone is designed to meet the demand of separating particles heavier or lighter than water simultaneously. Based on the conventional hydrocyclone, the structural modifications with a section in the middle and a volute chamber on the top of the hydrocyclone to accumulate the separated low density particles. Some factors that influence the separation efficiency of hydrocyclone were investigated in this paper. For the heavy phase, those influencing factors included the inlet flow rate and underflow split ratio. For the light one, different outlets for discharging the light phase were taken into account. The results show that there exists an optimum inlet flow rate for a series of underflow split ratios. The top outlet for separating light phase particles is better than the side outlet's.

Numerical Modeling of Venturi Flows for Determining Air Injection Rates Using Fluent V6.2

As the water passes through a restriction in a pipe, it forms a vacuum at the end of the restriction. A hole bored into the pipe at a point where this vacuum occurs will cause air to be drawn into the main flow. One example of this mechanism is seen in the venturi tube. When a minimal amount of differential pressure exists between the inlet and outlet sides of the venturi tube, a vacuum occurs at suction holes of the venturi tube. Venturi aeration is a method of aeration that has become popular in recent years. In present paper, air injection rates of venturi tubes are analyzed using Computational Fluid Dynamics modeling. These analyses are carried out by means of the program FLUENT V6.2 that uses finite volume theory. There is a good agreement between the measured air injection rates and the values computed from FLUENT CFD program.

Hydrogen gas-driven permeation through the membrane with asymmetric surface conditions

Permeation through the membrane with different surface conditions on the inlet and outlet sides is analyzed. Two regime parameters characterizing the rates of processes on two sides of the membrane with respect to the rate of bulk diffusion are introduced. These regime parameters determine the concentration profile and the permeation rate. General equations for the concentration and the permeation flux are obtained. Three basic limit regimes are considered as partial limit cases of the general equations. These are diffusion limited regime (DLR), outlet surface limited regime (OLR), and inlet surface limited regime (ILR). The latter has two modes with qualitatively different concentration profiles. Boundaries between the regimes and approximation formulas for the permeation rates in these regimes have been found. Features of permeation in the limit cases and in intermediate regions are analyzed.

Self-Assembled Ultra-thin Silica Layers for On-Chip Chromatography

AbstractWe propose a novel method for self-assembled packing of silica microsphere in micro-channel which can be potentially used for on-chip chromatography. Chromatography has been one of the most widely used techniques for the analysis and separation of the mixtures of biochemical compounds in research laboratories and industrial factories. Numerous chromatography techniques such as High-Performance Liquid Chromatography (HPLC), Thin Layer Chromatography (TLC) use absorbents (ex: silica, alumina, cellulose) as stationary phase material [1]. Effective loading of absorbents in those techniques has been a huge challenge since it requires additional implementation of high-pressure pump system (for HPLC) or limits selective coating of absorbents on supporting plate (for TLC). In order for chromatography to be efficiently integrated with micro-fluidic Lab-on-a-chip devices, novel techniques for easy and simple packing of absorbents within micro channels should be developed.Solvent-evaporation based 2-D crystallization technique [2] can enable mono-dispersed micro-particles to be self-assembled by capillary attractive forces. We apply this technique to assemble dense packing of silica microsphere and form ultra thin layers (2˜3 layers) within open microchannel. Open micro-channel has been constructed by conventional photolithography of SU8 photoresist. A small droplet (Volume: 0.1μL) of silica suspension (Diameter: 3μm, Solvent: DI Water, Concentration: 1.25wt%) has been placed in the defined inlet of micro channel. Capillary force within the open SU8 microchannel induces the flow of silica suspension in the channel. The packing of microsphere starts from the outlet side of the channel, where the thickness of solvent drastically decreases due to sudden increase of cross-sectional area of channel, and this packing propagates to the inlet side of the channel until solvent evaporates completely. As a result, a dense packing of silica microspheres are successfully assembled and a thin layer of silica microspheres are formed within open micro-channel.We will present the characterization of silica packing with regard to various process parameters and also will include theoretical interpretation of this packing technique in more detail. We will also present our future approach to integrate our technique on-chip chromatography applications.

Evaluation of alternative arrangements of a heat pump system for plume abatement in a large-scale chiller plant in a subtropical region

Heat pumps could be used to produce hot water for hybrid cooling towers for preventing the occurrence of plume in subtropical regions. The evaporative side of the heat pump system could be arranged either at the inlet side or at the outlet side of these cooling towers for cooling down the cooling water temperature. Alternatively, the evaporative side of the heat pump system could also be arranged at the evaporative side of chillers to reduce return chilled water temperature and therefore to reduce the cooling load of chillers. This study presents the evaluation of the impacts of these three arrangements of the heat pump system on the plume control performance and the energy performance in a large-scale chiller plant in Hong Kong. The performance prediction and evaluation of the chiller plant and the plume abatement system were conducted on a dynamic simulation platform. The results show that these three arrangements have almost the same plume control performance with sufficient plume control capability. The results also show that the arrangement of the evaporative side of the heat pump system for cooling down return chilled water temperature has much better performance that the other two arrangements for improving the overall energy efficiency.

주기관 쟈케트냉각수 온도를 위한 피드포워드 제어시스템의 구성과 분석

Keeping cooling water temperature higher within the allowable range helps marine engines to run in more efficient condition especially when the engine load is low. Temperature control of jacket cooling water in outlet side of main engine has been more widely adopted to ships these days for the purpose to reduce fuel consumption rate. But If the temperature sensor for the control loop is placed at the outlet of engine, it brings more difficulties in attaining stable and desirable properties due to dead times included in pipe length and engine itself comparing to the case where the measuring point is at the inlet side of main engine. In relation with this problem, Feed-forward control could be one of realistic solutions as it reveals good properties and requires less cost for system configuration. This study suggests a forward control system which leads to improved temperature control performances to disturbance signals which could arise from variation of engine load or weather condition. Two dead times in the modelling were described, considering pipe length between the actuator and the engine as well as the thermal process inside the engine. The results of analysis were shown by simulations to confirm responses under different conditions.

Determination of Pesticide Residues in Cereals by Liquid Chromatography and UV Detection

A chromatographic method to determine pesticide residues in cereals by high-performance liquid chromatography (HPLC) and ultraviolet (UV) detection has been described. The study focused on the preliminary purification procedure because of the analytical problems associated with the presence in these food matrices of high-molecular-weight compounds, such as lipids, triglycerides, celluloses, and starch, which can interfere and reduce the chromatographic separation efficiency of the analytes. The method proposed is based on the extraction of pesticide residues from 5 g of sample extracted with the use of petroleum ether and on cleanup with a C18 cartridge. The pesticides were eluted with acetonitrile. The column packed with solid support was eluted with a suitable solvent, and only a portion of flow outlet side of the UV detector was collected. Using the information of standard UV trace, it was possible to establish an appropriate portion and to ensure the collection of all pesticides analyzed. The simple and rapid proposal method has shown good recovery (70–110%) for different spiked levels of samples (0.025–0.1 mg/Kg) and could be applied to other food matrices that containing high-molecular-weight compounds.

Alloying effects of Ru and W on the resistance to hydrogen embrittlement and hydrogen permeability of niobium

The alloying effects of ruthenium and tungsten on the hydrogen solubility, the resistance to hydrogen embrittlement and the hydrogen permeability are investigated for Nb–M (M = Ru and W) alloys. The hydrogen solubility decreases by alloying and also by increasing the temperature of the alloy. As a result, the resistance to hydrogen embrittlement is improved owing to the low hydrogen content in the alloy. On the other hand, the hydrogen flux increases with increasing hydrogen concentration difference, Δ C, between the inlet and outlet sides of the alloy membrane. It is found that Nb–5 mol%X (X = Ru and W) alloys possess excellent hydrogen permeability without showing any hydrogen embrittlement when used under the appropriate permeation conditions of the temperatures and hydrogen pressures.

Analysis of hydrogen diffusion coefficient during hydrogen permeation through niobium and its alloys

The hydrogen solubility and the hydrogen permeability of Nb-based hydrogen permeable membranes are investigated in order to examine the hydrogen diffusion coefficient during the hydrogen permeation at high temperatures. It is shown that the hydrogen dissolution reaction into niobium and its alloys does not follow the Sieverts’ law at the pressure conditions of the practical hydrogen permeation, in contrast to the case of Pd-based alloys. The hydrogen diffusion coefficients during the hydrogen permeation are evaluated from a linear relationship between the normalized hydrogen flux, J· d, and the hydrogen concentration difference, Δ C between the inlet and outlet sides of the membrane with the thickness of d. It is found that the hydrogen diffusion coefficient for pure niobium is much lower than the reported values measured for dilute hydrogen solid solutions. Surprisingly, the hydrogen diffusion is found to be faster in Pd–Ag alloy with face-centered cubic (fcc) crystal structure than in pure niobium with body-centered cubic (bcc) crystal structure at 773 K during the hydrogen permeation. It is also found that the addition of Ru or W into niobium increases the hydrogen diffusion coefficient under the practical conditions.

Determination of sorption properties of intact rock samples: New methods based on electromigration

Two new methods for determining sorption coefficients in large rock samples have been developed. The methods use electromigration as a means to speed up the transport process, allowing for fast equilibration between rock sample and tracer solution. An electrical potential gradient acts as a driving force for transport in addition to the concentration gradient and forces the cations through the rock sample towards the cathode. The electrical potential gradient induces both electromigration and electroosmotic flow with a resulting solute transport that is large compared to diffusive fluxes. In one of the methods, the solute is driven through the sample and collected at the outlet side. In the other, simpler method, the rock sample is equilibrated by circulating the solute through the sample. The equilibration of rock samples, up to 5 cm in length, with an aqueous solution has been accomplished within days to months. Experiments using cesium as a sorbing tracer yield results consistent with considerably more time demanding in-diffusion experiments. These methods give lower distribution coefficients than those obtained using traditional batch experiments with crushed rock.

Development And Evaluation Of A Prototype Household Wooden Silo

A prototype household wooden silo with 8 kg capacity for storing shelled maize was designed, constructed and evaluated for performance. The structure was rectangular in shape, of total height of 0.6 m and width of 0.3 m, with a conical top inclined at an angle of 30 º with 0.1 m height and 0.3 m width. The silo had a top inlet for loading and side outlet for unloading the grains. Air-dried maize at moisture content of 13.2 % (dry basis) was stored in the silo for a period of two months. During storage, there was 9.5 % significant change in the moisture content of the maize, without mould growth or microbial infestation. Journal of Applied Science and Technology Vol. 12 (1&2) 2007: pp. 114-117

Experimental investigation of the performance of a Ranque–Hilsch vortex tube with regard to a plug located at the hot outlet

In this study, effects of position, diameter (5, 6, 7, 8 mm) and angle (30°–180°) of a mobile plug, located at the hot outlet side in a Ranque–Hilsch Vortex Tube (RHVT), were determined experimentally for best performance. In addition to plug parameters, effects of supply pressure (200–420 kPa) and number of nozzles (2, 4, 6) were also studied. The internal diameter ( D) of the vortex tube used in the experiments was 9 mm; the ratio of the length of the vortex tube to its diameter ( L/ D) was 15. Four different plug locations were studied. The maximum difference in the temperatures of hot and cold streams was obtained for the plug diameter of 5 mm, tip angles of 30° and 60°, 4 nozzles and by keeping the plug location at the far extreme end.