Use Of Baffles Research Articles

Towards steady-state direct solid sample analysis by inductively coupled plasma atomic emission spectrometry: qualitative evaluation of an intraplasmic powdered sample digester

A new type of reactor designed for continuous halogen-assisted digestion and analysis of powdered samples was evaluated. Two different halogenating gas introduction methods were tested, as well as the use of an internal baffle to increase the residence time of the solids inside the reactor. Studies were carried out on Al 2O 3 and CuO as model compounds for optimization of the reactor's parameters, such as the carrier gas flow, the fraction of halogenating gas and the feed rate, using Freon-12 as the halogenating gas. A qualitative study of a pseudo fluidized bed reactor (PFBR) was also performed on a soil sample certified reference material (SO-4). The internal gas flow rate had to be kept to an absolute minimum in order to minimize cooling of the PFBR's inner walls. Pre-mixing of the halogenating reagent into the solid aerosol carrier resulted in a much more efficient reaction than separate flow introduction. The use of a baffle drastically improved the digestion efficiency by virtue of an increased solid residence time. The argon plasma did not have a sufficiently high heat transfer capability to ensure proper operation of the PFBR under continuous sample loading. The porosity of the graphite used for the PFBR construction caused some tailing and memory effects due to analyte seepage into the reactor's walls.

Evaluation of eutrophication control strategies for the Keban Dam reservoir

The reservoir of the Keban Dam in eastern Anatolia is a very deep and large water body subject to significant seasonal water level fluctuations within a given hydrological year. At the present time, different sections of the reservoir have different trophic status and the upper portion of the reservoir, in particular, is eutrophic. In this regard, there is a need for the assessment of alternative strategies to be implemented for phosphorus and thus eutrophication control in this segment of the reservoir. In this study, mathematical modeling techniques are used to compare various alternatives in terms of their relative effectiveness for phosphorus control. With this intention, a two dimensional depth-averaged hydrodynamic model and a three-dimensional compartmental water quality model are coupled to represent the complex water body dynamics prevailing in the reservoir. After calibration and verification, the coupled model was used to simulate dissolved oxygen and euphotic chlorophyll- a concentrations under different scenario conditions corresponding to various strategies proposed for phosphorus control. The modelling effort has yielded valuable information that can be used by decision makers for the evaluation of different management alternatives including reduction of the phosphorus load coming from point as well as diffuse sources within the catchment area, use of baffles and construction of pre-dam structures.

Roles of baffles in waste stabilization ponds

Performance of baffles in waste stabilization ponds (WSP) comprising laboratory-scale ponds with different number of baffles was evaluated. This study was aimed at promoting waste stabilization ponds practice for wastewater treatment in tropical countries by reducing the land area requirement through the use of baffles which increased the biofilm and biomass concentrations. The experiments started with the tracer study to find out the hydraulic characteristics of each pond. It was shown that the dispersion number decreased with increasing flow length and number of baffles, which indicates more plug flow conditions. The deviation of actual HRT from theoretical HRT was computed and the flow pattern suggested the existence of an optimum spacing of baffles in baffled waste stabilization pond (BWSP) units. The investigations by feeding with synthetic wastewater further revealed that more than 65% TN and 90% NH3-N removal were achieved at HRT of 5 days in 6-baffled pond which corresponds to the specific area of 35.20 m2/m3. TN and NH3-N removal was increasing with number of baffles in the BWSP units. COD removal increased with higher number of baffles with its maximum removal efficiency at 6 baffles. The computed COD removal encompassed first-order reactions of both suspended and biofilm biomass was higher than that without the biofilm biomass activity and agreed well with the observed data. Compared with normal WSP, BWSP gave higher TN, NH3-N and COD removal. The effluent SS concentrations from 6 baffled-pond were less than 20 mg/l at HRT of 3 days.

Roles of baffles in waste stabilization ponds

Performance of baffles in waste stabilization ponds (WSP) comprising laboratory-scale ponds with different number of baffles was evaluated. This study was aimed at promoting waste stabilization ponds practice for wastewater treatment in tropical countries by reducing the land area requirement through the use of baffles which increased the biofilm and biomass concentrations. The experiments started with the tracer study to find out the hydraulic characteristics of each pond. It was shown that the dispersion number decreased with increasing flow length and number of baffles, which indicates more plug flow conditions. The deviation of actual HRT from theoretical HRT was computed and the flow pattern suggested the existence of an optimum spacing of baffles in baffled waste stabilization pond (BWSP) units. The investigations by feeding with synthetic wastewater further revealed that more than 65% TN and 90% NH3-N removal were achieved at HRT of 5 days in 6-baffled pond which corresponds to the specific area of 35.20 M2/m3. TN and NH3-N removal was increasing with number of baffles in the BWSP units. COD removal increased with higher number of baffles with its maximum removal efficiency at 6 baffles. The computed COD removal encompassed first-order reactions of both suspended and biofilm biomass was higher than that without the biofilm biomass activity and agreed well with the observed data. Compared with normal WSP, BWSP gave higher IN, NH3-N and COD removal. The effluent SS concentrations from 6 baffled-pond were less than 20 mg/l at HRT of 3 days.

Use of a Helical Baffle for Red Wine Clarification on a Mineral Membrane

Abstract We present the use of a helical baffle inserted in a mineral membrane (Carbosep) for the clarification of a highly charged red wine. Baffles of different geometries were made of stainless steel by winding a steel wire on a rod. The baffles were centrally placed. The wine was analyzed before and after its clarification for its filtration index, turbidity, color, and microbiological control. Experiments made at different transmembrane pressures and feed flow rates show that the permeate flux increased from 13 L/h·m2 (without baffle) to 30 L/h·m2 (with baffle). Long-term experiments at the same hydraulic dissipated energy gave a mean permeate flux of about 20 L/h·m2 from a baffled membrane compared to 10 L/h·m2 for a membrane without a baffle. The volume of permeate collected during the same time was 145% more for a baffled membrane. It was found that membrane fouling due to polarization concentration was reduced by a factor of 3 with the use of baffles. Analysis of permeate at three optical densiti...

Determination of the reaction of a continuous baffle wall with a rectangular cross section

1. The drag coefficients were determined experimentally for a rapid flow past a continuous wall of rectangular cross section with a height in the range C/h1=1/3–5/3 for Foude numbers from 20 to 110. 2. It was shown that the reaction related from the effect of the forward flow on the upstream face of the wall is negligibly small if the wall is located lower than the front part of the roller of the jump at a distance of more than 3.5–4 jump heights; the given wall can be regarded as a spillway. 3. The possibility of extrapolating dependence (7) for determining the optimal wall height for which a minimum lower pool depth is needed for submergence of the jump, from Fr=100 to Fr=200, was confirmed. 4. After substantiation, the use of baffles or basin with a length of not more than 1.5 jump heights can be recommended.

Nitrogen removal in baffled waste stabilization ponds

This study evaluated nitrogen removal in Baffled Waste Stabilization Ponds (BWSPs) comprising laboratory and pilot-scale ponds with different number of baffles. The aim was to promote the waste stabilization pond practice for wastewater treatment in tropical countries by increasing nitrogen and organic carbon removal efficiency or reducing the land area requirement through the use of baffles which increased the biofilm biomass concentrations. The experiments started with a tracer study to find out the hydraulic characteristics of each pond. It was shown that the dispersion number decreased with increasing flow length and number of baffles which indicated more plug flow conditions. The deviation of actual HRT from theoretical HRT was computed and the flow pattern suggested the existence of an optimum spacing of baffles in BWSP units. The investigations further revealed that more than 65% TN and 90% NH3-N removal efficiencies were achieved at HRT of 5 days in a 6 baffled pond, which corresponds to the specific area of 34.88 m2m3. TN and NH3-N removal increased with increasing number of baffles in the BWSP units. Combined algal/bacterial biofilm grown on the baffles immersed in the ponds showed potential for increasing the extent of nitrification. COD removal increased with higher number of baffles with its maximum removal efficiency at 6 baffles. Compared with normal WSP, BWSP gave higher TN, NH3-N, COD and BOD5 removal efficiency. The effluent SS concentrations from the laboratory-scale 6 baffled pond were less than 20 mg/L at HRT of 3 days or more.

Nitrogen removal in baffled waste stabilization ponds

This study evaluated nitrogen removal in Baffled Waste Stabilization Ponds (BWSPs) comprising laboratory and pilot-scale ponds with different number of baffles. The aim was to promote the waste stabilization pond practice for wastewater treatment in tropical countries by increasing nitrogen and organic carbon removal efficiency or reducing the land area requirement through the use of baffles which increased the biofilm biomass concentrations. The experiments started with a tracer study to find out the hydraulic characteristics of each pond. It was shown that the dispersion number decreased with increasing flow length and number of baffles which indicated more plug flow conditions. The deviation of actual HRT from theoretical HRT was computed and the flow pattern suggested the existence of an optimum spacing of baffles in BWSP units. The investigations further revealed that more than 65% TN and 90% NH3-N removal efficiencies were achieved at HRT of 5 days in a 6 baffled pond, which corresponds to the specific area of 34.88 m2/m3. TN and NH;-N removal increased with increasing number of baffles in the BWSP units. Combined algal/bacterial biofilm grown on the baffles immersed in the ponds showed potential for increasing the extent of nitrification. COD removal increased with higher number of baffles with its maximum removal efficiency at 6 baffles. Compared with normal WSP, BWSP gave higher TN, NH3-N, COD and BOD5 removal efficiency. The effluent SS concentrations from the laboratory-scale 6 baffled pond were less than 20 mg/L at HRT of 3 days or more.

Effects of Gull-Wing Baffles on the Performance of a Single-Row, Annularly Finned Tube Heat Exchanger

The effect of gull-wing baffling on the performance of a single-row, annularly finned tube heat exchanger is quantified for Reynolds numbers from 5,000 to 13,000. A novel adaptation of the naphthalene sublimation technique provides optically measured sublimation depths that are used to determine local mass-transfer coefficients with a spatial resolution superior to previously reported data. Local and average heat-transfer data for baffled and unbaffled finned tubes are inferred through the analogy between heat and mass transfer. Local data are used to explain the flow and heat-transfer interactions and their impact on overall heat-transfer performance. Pressure drop data are presented for a complete measure of heat-transfer and pumping power performance, and a performance evaluation criterion is used to compare the heat exchangers. The data indicate that the unbaffled geometry provides nearly the same heat transfer as the baffled arrangement, but the unbaffled geometry incurs only 20 to 25% of the baffled pressure drop in the Reynolds number range studied. The use of baffles as a heat-transfer enhancement method should be restricted to very low Reynolds numbers or to applications where pressure drop is not a factor.

Use of baffles in cavity flow for the suppression of thermal oscillations under microgravity

The quality of crystals grown from melt depends on the flow field in the melt. To simulate melt conditions, a finite element analysis is performed on flow in a heated cavity under the driving forces of natural convection, thermocapillary effects and rotation. In addition, the gravity field is modulated to simulate a microgravitational environment. The purpose for conducting this research is to determine whether the use of baffles can effectively reduce convection and suppress temperature oscillations. The results show that the baffle is able to suppress convection and reduce the amplitude of the temperature oscillations when placed perpendicular to the modulation direction. Under crystal and crucible rotation, the results with and without baffles are similar. In all cases, baffles did not induce temperature oscillations. From this study, it can be concluded that the effects of baffles on the flow behaviour depends greatly on the direction of gravity modulation and frequency.

TVA pilot-plant phosphate flotation conditioning study

TVA conducted an extensive test program in its 1,000-pound-per-hour phosphate beneficiation pilot plant to study the effects of major variables in the conditioning step prior to phosphate flotation. Florida rock fine flotation feeds of 14 and 18 bone phosphate of lime (BPL) from the Bone Valley formation were tested. During Phase I for each flotation feed, a full factorial design was used for the test series to evaluate the effects of agitation, retention time, and solids content on P2O5 recovery and product grade. In Phase II, a qualitative test study was completed of several additional variables including agitator flow direction, slurry feed position, use of baffles or no baffles, fuel oil to fatty acid ratio, and reagent dosage. The results of both test series were statistically analyzed and compared with those obtained from batch, laboratory-scale flotation tests of pilot plant conditioned samples. From the pilot-scale results, a mathematical model was developed relating product grade and P2O5 recovery to the major process variables.

Characteristics and performance of the Los Alamos VUV beamline at the NSLS

We describe the design and performance of the Los Alamos VUV synchrotron radiation beamline, U3C, on the VUV ring of the National Synchrotron Light Source at Brookhaven National Laboratory. The beamline uses separate function optics to collect and focus the horizontally and vertically diverging beam. The monochromator is a grazing incidence Rowland circle instrument of the extended grasshopper design (ERG). A postmonochromator refocusing mirror is used to focus or collimate the diverging beam from the monochromator. The beamline control and diagnostics systems are also discussed. Particular emphasis in the design has been placed on the reduction of stray and harmonic light. Higher order light is reduced by a grazing angle mirror low pass filter installed immediately downstream from the monochromator while stray light is reduced through the use of baffles and thin film filters. Also included in the line is a differential pumping section that permits gas phase and other experiments requiring pressures in the 10 −5 to 10 −4 Torr range to be coupled to the beamline.

Precipitation of hydrogen in crystalline silicon

The behavior of hydrogen in semiconductors has been a topic of increasing interest in recent years. The interest is in part stimulated by the ability of hydrogen to remove the electrical activity (passivate) of both dopant impurities and deep-level defects at moderate temperatures (<300C). Hydrogen is known to readily diffuse in silicon resulting in the neutralization of shallow-acceptor and shallow-donor dopants, Controlled studies of the role of hydrogen in silicon has been recently reported. This was achieved by exposing silicon single crystals to monoatomic hydrogen or deuterium from a microwave gas discharge. To prevent the radiation damage that results from direct exposure to the plasma, the specimens were mounted on a hot stage that was located down stream from the plasma. Optical isolation was achieved with the use of baffles. The specimen temperature was held constant in the range of 100-400°C for time intervals between 10-120 minutes.

Residence Time Distributions of Shallow Basins

An analysis of data from a variety of basins showed that the strongest influence on hydraulic efficiency, t¯/T, was that of the lengthto‐width ratio, L/W. Wind and depth also had some influence. Equations were derived to show these influences and to predict t¯/T, so designers can know how much to increase the ideal retention time. The L/W ratio can be increased, and the adverse effects of wind can be decreased, by the use of baffles. Two baffles, producing an L/W ratio of 5–10, are usually sufficient.

Performance of air-to-water copper finned-tube heat exchangers at moderately low air-side Reynolds numbers, including effects of baffles

The effects of ‘T baffles’ upon the performance of a copper finned-tube air-to-water heat exchanger are considered. Basic techniques for quantifying heat exchanger performance are reviewed. Convective heat transfer coefficients are presented as plots of Colburn j-factor vs Reynolds number based on hydraulic diameter. Test data are extended to include lower air flow rates than were previously reported in the literature. Friction effects induced by the use of baffles are also examined and presented as plots of friction factor vs Reynolds number.

Satellite-antenna measurement techniques

Initially, the review takes a brief look at the various types of antenna systems that are used on satellites and shows that in terms of the measurement of their radiation characteristics, they can be categorised into two groups, i.e. low-gain (omnidirectional and quasi-omnidirectional) antennas, and medium- and high-gain antennas. With the first group, the main measurement difficulty lies with the suppression of multipath reflections, and the various range configurations that can be used to avoid or overcome this problem are described. Two of these are, for example, the ground reflection mode range and the use of baffles within an anechoic chamber. Following this, direct measurement ranges applicable to medium- and high-gain antennas are reviewed. These far-field approximation test range configurations include the elevated mode range, either in an outdoor environment or within an anechoic chamber, and the semi-open anechoic chamber. Subsequently, the review considers the various near-field and intermediate distance methods. Finally, some special techniques that have been devised to examine some particular satellite-antenna problems, such as the determination of the r.f. transparency of launch vehicle fairings and the effect of conductive thermal-control paint on satellite-reflector antennas, are presented. The review is principally from a European viewpoint.

Cavity Radius vs Energy Dissipation Rate in Liquid-Filled, Precessing, Spherical Cavities

Theme E results and an idealized model are presented that yield energy dissipation rates as a function of radius for liquid-filled, precessing, spherical cavities. Experiments were conducted using cavities 11, 16.5, and 22cm in diameter and filled first with water to give turbulent flow conditions, and next with a silicone liquid (v = 1000 cs) to give laminar flow conditions. The objective of the experiments was to determine whether energy dissipation would be minimized, for a given mass of liquid, by using many small cavities rather than one, or a few, large cavities. An affirmative result would indicate that the use of baffles in a large cavity might, in the same manner, reduce energy dissipation.

Suppression of Transducer Sidelobes by the Use of Acoustic Baffles

The out-of-beam response of underwater acoustic transducers may be reduced by the use of baffle systems. This paper presents the results of experimental work carried out recently at the University of Birmingham (U.K.) on the effect of high-transmission-loss pressure-release planar baffles placed to the side of the main axis of a transducer. The height of the baffle (i.e., its projection beyond the transducer face) and the distance in wavelengths from the transducer axis have been varied over a wide range. Our results are compared to values calculated on the basis of Fresnel diffraction theory.

Occurrence of Gas-Bubble Disease in Three Species of Bivalve Molluscs

Gas-bubble disease was observed in adult oysters and hard clams held in heated running sea water during the winter. Heating the cold sea water in closed heat exchangers caused it to become supersaturated with atmospheric gases. Exposure of the animals to this water caused the formation of gas-filled conchiolin blisters on the valves of the oysters. Bubbles of gas were observed in the gill filaments of the oysters and clams and in the mantle tissue of the oysters. Any method, such as the use of baffles or an aerated head tank, that reduces the dissolved gas concentration in the water will help prevent the disease.

A Clean Vacuum Electron Beam Column for Cathodoluminescence Investigations

An instrument is described for investigation of cathodoluminescence at temperatures between 25 and 400 K and beam voltages to 50 kV. Contamination effects are minimized by the use of oil-free pumps, by isolation of the specimen region from sources of organic vapors, and by the use of baffles at liquid nitrogen temperature above and below the specimen region. Preliminary results on the cathodoluminescence of GaAs are reported and compared with the temperature dependence of the bandgap from optical absorption data.