Gas Flow

An analytical model for gas-solid suspension flow through an inclined section of pipe was developed. This model predicts the ratio of the total pressure drop in an inclined pipe to that of a horizontal pipe. The model has been used to predict the critical pipe angle, which is defined as the angle at which the maximum pressure drop for a given solids flow rate is achieved. This angle differs from 90 ° (found in a single-phase flow) and is directly proportional to the ratio between the gas superficial velocity and the particle terminal velocity. The three-dimensional conservation equations for steady-state two-phase flow in an inclined pipe were solved numerically for constant solids and gas flow rates at different pipe inclinations. This model was based on the continuum theory for describing the mass and momentum balance equations for the fluid and solid phases. A packing model, describing the shear stress of the solid phase as a function of its volume fraction, is suggested in order to limit the maximum value of the solid volume fraction. A new model for particle-wall interaction was developed taking into account the angle of inclination of the pipe. The prediction of the numerical model was compared with experimental data obtained in a specially designed test rig. In general, the agreement between the experimental data and the models was satisfactory. The results of the numerical simulation also confirmed that the critical pipe angle for gas-solid flow is lower than 90 ° . The assumptions made during the development of the models were assessed in order to explain the differences between the predicted and measured values of the flow parameters for different flow regimes. © 1997 Elsevier Science S.A.

The influence of temperature (10-45°C), feed flow rate (300-500 L/h) and sweeping gas flow rate (1.2-2 m 3 /h) on the recovery of berry fruit juice aroma compounds by sweeping gas membrane distillation (SGMD) was examined on an aroma model solution and on black currant juice in a lab scale membrane distillation set up. The data were compared to recovery of the aroma compounds by vacuum membrane distillation (VMD). The flux of SGMD increased with an increase in temperature, feed flow rate or sweeping gas flow rate. Increased temperature and feed flow rate also increased the concentration factors (C permeate /C feed ) of the aroma compounds. At 45°C the most volatile and hydrophobic aroma compounds obtained the highest concentration factors: 12.1-9.3 (black currant juice) and 17.2-12.8 (model solution). With black currant juice a volume reduction of 13.7% (vol.%) at 45°C, 400 L/h, resulted in an aroma recovery of 73-84 vol.% for the most volatile compounds. Compared to VMD, the aroma recovery with SGMD was less influenced by the feed flow rate but more influenced by the temperature. Higher fluxes were achieved during concentration by VMD and this reduced the operation time, which in turn reduced the degradation of anthocyanins and polyphenolic compounds in the juice. Industrial relevance: High temperature evaporation is the most widely used industrial technique for aroma recovery and concentration of juices, but membrane distillation (MD) may provide for gentler aroma stripping and lower energy consumption. This study gives important clues about the fate of berry juice aroma compounds and polyphenols during concentration by MD, and identifies the main factors influencing the aroma recovery efficiency with MD. Both SGMD and VMD are promising techniques for gentle stripping of berry juice aroma compounds and deserve further consideration as alternative techniques for gentle aroma stripping in industrial fruit juice processing.

We have developed a modified physical vapor transport (M-PVT) growth technique for the preparation of SiC single crystals which makes use of an additional gas pipe in order to control the gas phase composition of the conventional physical vapor transport (PVT) configuration. We discuss ...

Nitrogen doped silicon films have been deposited by low pressure chemical vapour deposition from disilane Si H and ammonia 2 6 NH . Deposition kinetics is investigated, pointing out the influences of the deposition temperature, the total pressure and the gas 3 flow rates. According to the Bruggeman theory, variations of the NH ySi H gaseous ratio allow for a wide range of the SiN 3 2 6 x stoichiometry as well as a good control of the film nitrogen doping. The different behaviours of the nitrogen atom in silicon films are discussed and an overview of the nitrogen doped silicon physical properties (optical, mechanical and electrical) is proposed for the development of boron-doped polysilicon gates. ᮊ

Performing experiments with transactinide elements demands highly sensitive detection methods due to the extremely low production rates (one-atom-at-a-time conditions). Preseparation with a physical recoil separator is a powerful method to significantly reduce the background in experiments with sufficiently long-lived isotopes (t 1/2 Z 0.5 s). In the last years, the new gas-filled TransActinide Separator and Chemistry Apparatus (TASCA) was installed and successfully commissioned at GSI. Here, we report on the design and performance of a Recoil Transfer Chamber (RTC) for TASCA-an interface to connect various chemistry and counting setups with the separator. Nuclear reaction products recoiling out of the target are separated according to their magnetic rigidity within TASCA, and the wanted products are guided to the focal plane of TASCA. In the focal plane, they pass a thin Mylar window that separates the $ 1 mbar atmosphere in TASCA from the RTC kept at $ 1 bar. The ions are stopped in the RTC and transported by a continuous gas flow from the RTC to the ancillary setup. In this paper, we report on measurements of the transportation yields under various conditions and on the first chemistry experiments at TASCA-an electrochemistry experiment with osmium and an ion exchange experiment with the transactinide element rutherfordium.

Sunflower is a traditional crop which can be used for the production of bioenergy and liquid biofuels. A study of the pyrolytic behaviour of sunflower residues at temperatures from 300 to 600°C has been carried out. The experiments were performed in a captive sample reactor under atmospheric pressure and helium as sweeping gas. The yields of the derived pyrolysis products were determined in relation to temperature, with constant sweeping gas flow of 50 cm 3 min À1 and heating rate of 40°C s À1 . The maximum gas yield of around 53 wt.% was obtained at 500°C, whereas maximum oil yield of about 21 wt.% was obtained at 400°C. A simple first order kinetic model has been applied for the devolatilization of biomass. Kinetic constants have been estimated: E = 78.15 kJ mol À1 ; k 0 = 1.03 · 10 3 s À1 .

Advanced pressurized fluidized bed combustors (PFBC) and integrated gasification combined cycles (IGCC) as economical clean coal technologies for the 21st century have attracted considerable attention. The success of these advanced coal energy systems hinges on effective and reliable commercial-scale filtration of gases at very high temperatures. The Pinon Pine hot-gas filtration system is the first industrial-scale application of an advanced particle filtration system in the United States. The system currently is becoming operational and will provide significant practical insights into operation of the industrial-scale hot-gas cleaning process.

We recorded high-resolution seismic-reflection data in the northern Gulf of Mexico to study gas and gas-hydrate distribution and their relation to seafloor slides. Gas hydrate is widely reported near the seafloor, but is described at only one deep drill site. Our data show highreflectivity zones (HRZs) near faults, diapirs, and gas vents and interbedded within sedimentary sections at shallow depth (, 1 km). The HRZs lie below the gas-hydrate-stability zone (GHSZ) as well as within the zone (less common), and they coincide with zones of shallow water-flows. Bottom simulating reflections are rare in the Gulf, and not documented in our data. We infer HRZs result largely from free gas in sandy beds, with gas hydrate within the GHSZ. Our estimates for the base BHSZ correlate reasonably with the top of HRZs in some thick well-layered basin sections, but poorly where shallow sediments are thin and strongly deformed. The equivocal correlation results from large natural variability of parameters that are used to calculate the base of the GHSZ. The HRZs may, however, be potential indicators of nearby gas hydrate. The HRZs also lie at the base of at least two large seafloor slides (e.g. up to 250 km 2) that may be actively moving along decollement faults that sole within the GHSZ or close to the estimated base of the GHSZ. We suspect that water/gas flow along these and other faults such as 'chimney' features provide gas to permit crystallization of gas hydrate in the GHSZ. Such flows weaken sediment that slide down salt-oversteepened slopes when triggered by earthquakes. Published by Elsevier Science Ltd.

We have employed computer-aided furnace design and process simulation to optimize the conditions under which single-walled carbon nanotubes (SWCNTs) may be grown in high yields on 4 in. wafers for electronic device applications. Hydrokinetic simulations were performed to obtain optimized furnace structures and process conditions in terms of gas flow, temperature, and gas speed. Shower head structures and a flow isolation barrier were installed in an experimental 6 in. furnace, as suggested by the hydrokinetic simulations. To ensure clean surfaces and uniform catalyst islands, catalyst patterns were lifted off using Au films or polydimethylsiloxane. Photolithography was used to fabricate field-effect transistors with SWCNTs grown on 4 in. wafer substrates. The total yield of the nanotube devices increased from 30.5% to 96.4% after optimization.

In this study, the heat utilisation efficiency of all commonly used cookstoves was measured with emphasis placed on natural gas cookstoves. In addition, two improved cookstoves developed by a research institution of Bangladesh (one for biomass and one for natural gas) were studied. The type of cooking vessel (roundbottomed pot and flat-bottomed pan) and the flow rate of gas (power) were the two parameters studied for natural gas cookstoves. The pan was found to give higher efficiencies in all cookstoves. With regard to power it was found that efficiency first increases and then decreases with increasing gas flow rate. An analysis of the design and performance of the existing natural gas cookstoves led to the development of a simple contrivance -a perforated sheet metal shield around the flame and a portion of the cooking vessel. The modified cooking system was found to increase the heat utilisation efficiency. The paper also presents the cost of cooking for different fuel-cookstove combinations.

Transparent conducting ZnO:F was deposited as thin films on soda lime glass substrates by atmospheric pressure chemical vapor deposition (CVD) deposition at substrate temperatures of 480–500 °C. The precursors diethylzinc, tetramethylethylenediamine and benzoyl fluoride were dissolved in xylene. The solution was nebulized ultrasonically and then flash vaporized by a carrier gas of nitrogen preheated to 150 °C. Ethanol was vaporized separately, and these vapors were then mixed to form a homogeneous vapor mixture. Good reproducibility was achieved using this new CVD method. Uniform thicknesses were obtained by moving the heated glass substrates through the deposition zone. The best electrical and optical properties were obtained when the precursor solution was aged for more than a week before use. The films were polycrystalline and highly oriented with the c-axis perpendicular to the substrate. The electrical resistivity of the films was as low as 5 × 10−4 Ωcm. The mobility was about ...

Spray prints of thermal spray coatings were created on glass slides for air-plasma-sprayed 8-wt %-yttria-partially-stabilized zirconia (YSZ) deposits. The spray parameters such as carrier gas flow rate, standoff distance, and torch power were systematically changed to investigate the influence of these parameters on the YSZ deposit characteristics. The deposit properties such as deposition efficiency (DE), substrate coverage, deposit thickness, and roughness were measured. The deposits sprayed with a 35-4.0 Llmin carrier gas flow rate at an 80 mm standoff distance exhibited higher values of DE within the range of studied process parameters. The DE increased as much as 25% by varying the carrier gas flow rate from 2.0 to 4.0 Llmin. The deposits sprayed at a higher standoff distance and low torch power gave poor deposit characteristics. The deposit characteristics were compared with the in-flight particle parameters and revealed that the deposit characteristics strongly depended on the in-flight particle temperature. Using the in-flight particle properties, the flattening ratio and the splat thickness were calculated. The average size of particles adhering to the substrate was found to drastically change with a change of process conditions, being much less than the average size of the starting powder. Sample Size= 3 i i ; 4 . 6 Carrier Gas Flow Rate (Vmin) Fig. 3. Change of deposition efficiency (DE) with the plasma spray variables.

Thermal and catalytic degradation of poly (vinyl chloride) (PVC) containing polymer mixtures, PVC/PE, PVC/PP and PVC/PS, into fuel oil was investigated. In the catalytic degradations, Red Mud (a waste from alumina production) was tested as both cracking and dechlorination catalyst. For comparison, g-Fe 2 O 3 as a chlorine sorbent and SA-1 (silica alumina) as a solid acid catalyst were also used. The effect of degradation conditions, such as nitrogen gas flow, stepwise pyrolysis, catalyst contact mode, on the dechlorination was also investigated. The use of N 2 gas flow suppressed partially the reaction between HCl gas from the degradation of PVC and polymer degradation products. By stepwise pyrolysis, over 90% chlorine in the feed plastic was recovered as HCl gas. SA1 catalyst accelerated the rate of polymer degradation and lowered the boiling point of liquid products, but the chlorine content of oil over SA1 was also the highest. Red Mud (RM) and iron oxides sorbents showed good effect on the fixation of evolved HCl. However, they had no effect on the cracking of polymers. The oils derived from PVC containing pure polymer mixtures by thermal degradation contained a lower amount of chlorine than the oils obtained using RM and other catalysts. From this result we conclude that the formation of some organic chlorine compounds may be promoted by the interaction of the HCl and the catalysts. #

A method is proposed to augment the proper orthogonal decomposition basis functions with discontinuity modes to better capture moving discontinuities in reduced-order models. Moving discontinuities can be shocks in unsteady gas flows or bubbles in multiphase flow. The method is shown to work for a simple test problem using the first-order wave equation. A method for detecting discontinuities numerically is developed using mathematical morphology. This method is shown to properly identify the edges of bubbles in multiphase flow.

The cyclone-type separator with swirling baffle and bottom take off of clean gas is a patented technique for separating solid particles from gases. Main relative dimensions of the separator are the same as given by Stairmand [C.J. Stairmand, The design and performance of cyclone separators, Trans. Inst. Chem. Eng. 29 (1951), 356–383] for the high efficiency cyclone. The principal part of the construction is the cylinder-shape swirling baffle with the flow gaps cut on its surface. The article presents the theoretical model of the new construction of cyclone-type separator with swirling baffle and bottom take off of clean gas. Calculational model to predict the collection efficiency was based on Leith and Licht cyclone calculational method [D. Leith, W. Licht, The collection efficiency of cyclone-type particle collectors — a new theoretical approach, AIChE Symp. Ser. 68 (126) (1972), 196–206]. The main assumption of the developed model is that the tangential velocity distribution is o...

A 3D numerical study was carried out to analyze flow, heat and mass transfer first in a single half-cell cathode channel of proton exchange membrane (PEM) fuel cell. From practical point of view, it is necessary to put the appropriate number of cells in a stack. Hence, the above study on a single half-cell is extended to a stack of channels. Due to stacking, the assumption of uniform flow distribution would no longer hold true. Therefore, the channel flow-maldistribution is considered. The water formed at the active surface due to the electrochemical reaction diffuses through the porous layer and eventually enters the gas flow duct. The higher gas velocities in the duct result in faster water vapour removal which leads to a lower value of water vapour into the duct and hence a lower Nusselt number.

The presence of noble gas and other short-lived radionuclides in air borne effluents from RBMK-1500-type reactor has been investigated using experimental and theoretical instrumentation for detection purposes. Activity concentrations of 85m Kr, 87 Kr, 88 Kr, 135m Xe, 135 Xe, 133 Xe and 41 Ar were measured in air emissions from Ignalina NPP using a special method and special equipment. Theoretical detection of reactor-borne radionuclides and investigation of their behaviour in a nuclear fuel during operation of nuclear reactor was performed using an analytical model based on reactor physics. An innovative method for the estimation of noble gas flow time from the defective nuclear fuel element through the ventilation stack of NPP to the atmosphere based on comparison of the experimentally and theoretically evaluated activity ratios of 88 Kr/ 85m Kr; 135 Xe/ 133 Xe has been proposed. The estimated flow time of noble gas provides an excellent possibility to obtain modelling-based information about the qualitative and quantitative content of atmospheric releases from NPP. r

Direct injection high efficiency nebulizer (DIHEN)-inductively coupled plasma mass spectrometry (ICPMS) is investigated for analysis of petroleum samples dissolved in volatile organic solvents. To minimize solvent loading, the solution uptake rate is reduced to 10 mlymin, far less than the level (85 mlymin) commonly used for aqueous sample introduction with the DIHEN, and oxygen is added to the nebulizer gas flow and outer flow of the ICP. Factorial design is applied to investigate the effect of nebulizer tip position within the torch and the nebulizer and intermediate gas flow rates on the precision and the net signal intensity of the elements tested for multielemental analysis. Cluster analysis and principal component analysis are performed to distinguish the behavior of different isotopes, oxide species and doubly charged ions. The best operating conditions at a solution uptake rate of 10 mly min are: RF powers1500 W, nebulizer gas flow rates0.10-0.12 lymin, intermediate gas flow rates1.5 lymin and DIHEN tip positions3-4 mm below the top of the torch intermediate tube. Acceptable recoveries (100"10%) and good precision (less than 3% relative standard deviation) are obtained for trace elemental analysis in organic matrices (a certified gas oil sample and a custom-made certified reference material) using flow injection analysis. Because of high blank levels, detection limits are 1-3 orders of magnitude higher for organic sample introduction than those acquired for aqueous solutions. ᮊ

A special bi-anode plasma torch that can change the anode arc root position without changing working gas flow rate has been developed to investigate the effect of anode arc root position on the behavior of the plasma jet. It has two nozzle-shaped anodes at different axial distances from the cathode tip. The arc root can be formed at anodes either close to the cathode tip (anode I) or far away from it (anode II) to obtain different attachment positions and arc voltages. The characteristics of pure argon plasma jets operated in different anode modes were measured in the field free region by using an emalpy probe, and the thermal efficiency of the torch was determined by measuring the temperature differences between cooling water flowing in and out of the torch. The results show that compared with the normal arc operated in anode I mode, the elongated arc operated in anode II mode significantly reduced the plasma energy loss inside the torch, resulting in a higher temperature and a higher velocity of the plasma jet in the field free region.

This paper studies the eciency of high-power laser methods for modifying the AISI 304 steel surface in order to increase its corrosion resistance. The surface of SS 304 was melted in argon and nitrogen atmospheres using dierent laser beam scan rates and gas¯ows. The results obtained show that in both cases the laser surface melting (LSM) induced improvements in pitting resistance with respect to the base steel. Electrochemical studies showed that the improvements are greater when the LSM is carried out in a nitrogen environment because of the incorporation of nitrogen into solid solution. As a result, the corrosion and pitting potential shift to more noble values while the passive current density decreases by nearly two orders of magnitude. The presence of chromium oxides and nitrogen compounds on the surface of the specimens seem to indicate that nitrogen may help the reconstruction of the passive layer as well as act as a barrier for the electrolyte. Ó

This study deals with the mineralization of N-methyl-2-pyrolidone (NMP) by ozonation in a semi-batch lab scale reactor. NMP degradation was not inhibited in the presence of hydroxyl scavengers at acidic medium (pH 3), which indicated that the degradation was only due to ozone. The direct reaction rate constant (k D ) was found to be 1.99 M −1 s −1 . The Effect of various physicochemical operating conditions for efficient mineralization was investigated. Total organic carbon (TOC) removal was efficient at pH 10 and 34.5% of TOC enhancement was noted when the solution pH increases from 3 to 10, which confirmed that radical induced mineralization was more efficient. The effect of various influent ozone gas dosages shows that 18.4 mg/(l min) was found to be optimum and further increase in the ozone dosage did not enhance the TOC removal rate. When the ozone gas flow rate increases from 100 ml/min to 300 ml/min, the volumetric mass transfer coefficient (k L a) increased as well. Increase in the reaction temperature from 5 • C to 50 • C enhances the TOC removal rate and the removal rate was not significant above 25 • C. The TOC removal and nitrate formation efficiencies of NMP at various advanced oxidation processes (AOPs) were in the following order UV/O 3 > O 3 > UV/H 2 O 2.

An experimental investigation of the entrainment in capillary-driven beat pipes was conducted to identify and better understand the parameters that govern the entrainment of liquid droplets in high velocity air streams flowing over capillary wicking structures. Using a flow visualization technique, two modes of entrainment were identified and described for high velocity convective air flows over an intermittently interrupted liquid surface similar to that occurring in heat pipe wicks.

A simple, economic diode laser based cavity ringdown system for trace-gas applications in the petrochemical industry is presented. As acetylene (C 2 H 2 ) is sometimes present as an interfering contaminant in the gas flow of ethylene (ethene, C 2 H 4 ) in a polyethylene production process, an on-line monitoring of such traces is essential. We investigated C 2 H 2 -C 2 H 4 mixtures in a gas-flow configuration in real time. The experimental setup consists of a near-infrared external cavity diode laser with an output power of a few mW, standard telecommunication fibers and a home-made gas cell providing a user-friendly cavity alignment. A noise-equivalent detection sensitivity of 4.5 × 10 −8 cm −1 Hz −1/2 was achieved, corresponding to a detection limit of 20 ppbV C 2 H 2 in synthetic air at 100 mbar. In an actual C 2 H 2 -C 2 H 4 gas-flow measurement the minimum detectable concentration of C 2 H 2 added to the C 2 H 4 gas stream (which may already contain an unknown C 2 H 2 contamination) increased to 160 ppbV. Moreover, stepwise C 2 H 2 concentration increments of 500 ppbV were resolved with a 1-min time resolution and an excellent linear relationship between the absorption coefficient and the concentration was found.

Activating, coating and curing processes are accomplished in-situ on rigid and flexible substrates using an atmospheric pressure plasma system. Liquid based precursors are injected into an ambient plasma jet whereby machine parameters allow for film thickness control. This paper summarizes the effect of varying process parameters on the deposition rate of a polymeric coating using a plasma jet system. A series of designed experiments were undertaken to monitor the deposition rate and coating chemistry of both fluorocarbon (heptadecafluorodecyl acrylate) and siloxane (Z-TOMCATS) films. Using a combination of ellipsometry and FT-IR measurements, it is clearly shown that coatings can be deposited with controlled functional chemistry using this system. It was found that the plasma power, precursor flow rate and the speed of the plasma system are significant factors which affect the deposition rate and the chemistry of the coatings. The coating process was not affected by variations in the gas flow parameters.

This paper describes the development of a novel modelling tool for evaluation of solid oxide fuel cell (SOFC) performance. An artificial neural network (ANN) is trained with a reduced amount of data generated by a validated cell model, and it is then capable of learning the generic functional relationship between inputs and outputs of the system. Once the network is trained, the ANN-driven simulator can predict different operational parameters of the SOFC (i.e. gas flows, operational voltages, current density, etc.) avoiding the detailed description of the fuel cell processes. The highly parallel connectivity within the ANN further reduces the computational time. In a real case, the necessary data for training the ANN simulator would be extracted from experiments. This simulator could be suitable for different applications in the fuel cell field, such as, the construction of performance maps and operating point optimisation and analysis. All this is performed with minimum time demand and good accuracy. This intelligent model together with the operational conditions may provide useful insight into SOFC operating characteristics and improved means of selecting operating conditions, reducing costs and the need for extensive experiments.

Objective: To compare in intubated patients manually ventilated in order to mirror the ventilator, the respiratory and hemodynamic effects induced by a bag device equipped with an inspiratory gas flow-limiting valve (Smart Bag, 0-Two Medical Technologies Inc., Mississauga, ON, Canada) and a Standard bag. Design: Non-randomized crossover study comparing 13 respiratory and eight hemodynamically paired parameters. Eight intubated patients were manually ventilated, each by three different intensive care workers yielding 24 sets of data for comparison. Data were collected during two sessions of manual ventilation, first with the Standard bag and then with the Smart Bag. Between each session, the patient was reconnected to the ventilator until return to the baseline. Patients, included after coronary surgery, were sedated and paralyzed. Setting: Intensive Care Unit, university hospital. Results: Compared with Standard bag, the Smart Bag ® provided a decrease of inspiratory flow (23 ± 4.7 vs. 47.3 ± 16.5 l/min) with a decrease

Plasma enhanced chemical vapor deposition (PECVD) of germanium selenide thin films from germanium tetrachloride and dimethyl selenide was studied to determine the viability of these reagents for thin film deposition. Germanium tetrachloride and alkylselenides were selected as candidates for these reactions due to their lower toxicities and higher availabilities compared to the more typical substitutes: germane and hydrogen selenide in the formation of germanium selenides. Dimethyl selenide was used successfully for the deposition of germanium selenides. Variation in film stoichiometry was observed by the modification of reactant gas flow ratios. Relative mass flow rates were varied in order to determine their effect on germanium chalcogenide deposition, and the effect of these flow rate modifications on the film thickness, structural properties, and composition are reported.

Addition of a calcium-based CO acceptor to commercial steam methane reforming catalyst permits the production of 95#% H in a single-step process. The combined reforming, shift, and CO separation reactions have been studied using a laboratory-scale "xed-bed reactor as a function of temperature, steam-to-methane ratio, acceptor-to-catalyst ratio, feed gas #ow rate, and methane content of the feed gas. The combined reactions were su$ciently rapid above 5503C that equilibrium was closely approached at all reaction conditions studied. The H content of the product gas was relatively independent of temperature with the primary impurity at lower temperatures being CH . Higher temperatures resulted in increased CH conversion but decreased carbon oxide removal leaving CO and CO as the primary impurities. Potential advantages of the single-step process, in addition to reducing the number of processing steps, include improved energy e$ciency, elimination of the need for shift catalysts, and reduction in the temperature of the primary reactor by 150}2003C. Key unanswered problems involving the single-step process include continuous separation of catalyst and acceptor and the durability of the acceptor for multiple cycle operation.

This paper focuses on the implementation of various diagnostics for optimizing chemical oxygen iodine laser. This paper also dwells on the measurement methodologies and instrumentation employed in these diagnostic systems. The prime diagnostics are for the measurement of vital species in form of iodine, singlet oxygen, and chlorine. Iodine concentration measurement (absorption at λ = 499 nm), chlorine utilization (absorption at λ = 330 nm), and singlet oxygen yield (emission at λ = 1.27 µm) have been implemented based on optical absorption/emission principle. Furthermore, online Mach number determination, which is critical for supersonic gas flows, laser pulse detection (at λ = 1315 nm), and flow rate measurement and control over wide range, have been carried out. A dedicated diagnostics and data acquisition system (DDAS) customized for parameter monitoring have been developed. The developed DDAS also serves the purpose of precise operation sequencing and parameter control. It is a 168-channel personal-computer-based system with customized interface electronics employing Visual C++ programming language with user-friendly graphical user interfaces. A detailed uncertainty analysis of various critical parameters has been also presented.

We have investigated the characteristics of Ar/O 2 plasmas in terms of the photoresist (PR) and low-k material etching using a ferritecore inductively coupled plasma (ICP) etcher. We found that the O 2 /(O 2 + Ar) gas flow ratio significantly affected the PR etching rate and the PR to low-k material etch selectivity. Fourier transform infrared spectroscopy (FTIR) and HF dipping test indicated that the etching damage to the low-k material decreased with decreasing O 2 /(O 2 + Ar) gas flow ratio.

A rapid liquid chromatography-atmospheric pressure photoionization mass spectrometry (LC-APPI-MS) method was developed for the determination of ergosterol in wheat grains. The effects of the dopants acetone, toluene and anisole on the ionization efficiency were studied. To identify the predominant ions, APPI-MS-MS studies were performed. Different LC and MS parameters were optimized to obtain maximum sensitivity. The effects of the mobile phase composition and of the flow rate were investigated. Additionally, the effects of the nebulizer gas pressure, the drying gas flow, the vaporizer temperature, the fragmentor voltage and the capillary voltage on the ionization efficiency were evaluated. The calibration curve exhibited good linearity and reproducibility. The detection limit (S/N = 3) was 0.15 ng on column, which allows the determination of ergosterol in wheat at a concentration as low as 0.12 g/g. Twenty wheat varieties artificially infected with Fusarium graminearum were investigated by this method.

Interfacial s t r e s s e s are calculated from new measurements of liquid height a n d p r e s s u r e d r o p for fully d e v e l o p e d horizontal stratified flow. T h e s e are related to w a v e properties. An improved d e s i g n m e t h o d is s u g g e s t e d .

The plasma spray process is widely used to produce thick coatings by the successive pilling of particles deposited in a molten or semi-molten state on a prepared substrate. However, this process includes time-dependent phenomena that affect the reliability of the process and reproducibility of coating. These phenomena are principally linked to the continuous movement of the electric arc root on the anode wall in the plasma gun. Such a movement leads to arc length variations resulting in fluctuations in arc voltage, enthalpy input to the flow and instabilities in the plasma jet. This paper presents an attempt to develop a time-dependent and 3-D model of the plasma spray process that can provide a useful insight in the time-evolution of the performance of the process. The effect of the transient behaviour of the arc on the gas flow is modelled with a time dependant heat source located inside the nozzle and evolving with the arc voltage. The first stage of the study consisted in the validation of the flow model thanks to the comparison of steady-state computed results with experimental data. The second dealt the time-dependant simulation of the flow.

This work addresses the robust output feedback tracking problem for a biological wastewater treatment process in the presence of input constraints and limited knowledge on the process parameters. The considered process is an anaerobic up-flow fixed bed biological reactor within a semi-industrial scale pilot plant for the treatment of industrial wine distillery wastewater. A mathematical model describing the dynamic behavior of the biological process is considered and nonlinear control techniques are used to design a bounded output feedback control law. Local asymptotic stability and local set-point tracking of the resulting closed-loop system is proved when the dilution rate is selected as the manipulated variable and the output methane gas flow-rate as the measured and controlled variable. Finally, the implementation of the nonlinear output feedback control law is described and experimental results are reported. It is observed that the proposed controller yields set-point regulation, rejects disturbances and preserves stability despite uncertainty on the kinetic parameters.

An integrated thermal sensor for flow rates below 200 sccm, consisting of two central heaters and two thermopiles, located downstream and upstream with respect to the heaters, is presented. The sensor, fabricated by post-processing chips produced with a standard microelectronic process, is operated in closed loop configuration through a single operational amplifier, in such a way that the flow-induced temperature difference between the two thermopiles is cancelled by applying a power mismatch to the two heaters. The output signal is proportional to the heater power unbalance. Static and dynamic electrical characterization of the sensor is performed. The response to nitrogen flow rates has been measured for various gas pressures.

Precursor nickel oxalate powder was entrained in pure argon and a 5% hydrogen-in-argon carrier gas flow and carried through a heated transport tube reactor. The reactor wall temperature was maintained at 748-1018 K for residence times less than 4 s. Rapid reaction was possible because of high particle heating rates. A 5% addition of hydrogen to the carrier allowed for the synthesis of a high-purity elemental nickel powder with low residual oxygen content. Product particles consisted of nano-sized primary particles contained within an overall microcontainer matrix. Primary nickel particles nucleated within the precursor microcontainer matrix, followed by a coalescence period. The product powder was characterized as 2-40 m diameter microcontainer particles comprised of nano-sized nickel primary particles with diameters of 20-70 nm. The production of porous elemental nickel powder via the aerosol flow thermal decomposition of nickel oxalate results in powder with acceptable electrical properties and is more benign and potentially cheaper than the current commercial process for nickel powder production.

Cooling towers are widely used in many industrial and utility plants as a cooling medium, whose thermal performance is of vital importance. Despite the wide interest in cooling tower design, rating and its importance in energy conservation, there are few investigations concerning the integrated analysis of cooling systems. This work presents an approach for the systemic performance analysis of a cooling water system. The approach combines experimental design with mathematical modeling. An experimental investigation was carried out to characterize the mass transfer in the packing of the cooling tower as a function of the liquid and gas flow rates, whose results were within the range of the measurement accuracy. Then, an integrated model was developed that relies on the mass and heat transfer of the cooling tower, as well as on the hydraulic and thermal interactions with a heat exchanger network. The integrated model for the cooling water system was simulated and the temperature results agree with the experimental data of the real operation of the pilot plant. A case study illustrates the interaction in the system and the need for a systemic analysis of cooling water system. The proposed mathematical and experimental analysis should be useful for performance analysis of real-world cooling water systems.

Experiments were conducted with air-water flow in a horizontal 0.095-m pipeline at atmospheric pressure to examine the mechanism by which slugs form in a stratified flow. A specially designed entrance box was used to avoid disturbances. In these experiments, at superficial gas velocities less than 3 m/s, the slugs are found to evolve from waves, with a length of about 0.085 m, that are generated by a Jeffreys mechanism. These waves grow in height and eventually double in wavelength by a nonlinear resonance mechanism. Depending on the height of the liquid, the growth can lead to a breaking wave or to a wave that fills the whole pipe cross section. At superficial gas velocities equal to or greater than 4 m / s capillary-gravity waves with a wide range of lengths are generated by a linear Kelvin-Helmholtz mechanism. These rapidly evolve into long waves outside the range of linear instability. If the liquid height is large enough, these waves can form slugs through a nonlinear Kelvin-Helmholtz instability that is aided by wave coalescence. 2. Fan is currently at Fractionation Research, Stillwa:er, OK. F. Lusseyran is visiting scientist from LEMTA-ENSEM, Nancy, France. (an imbalance between energy fed to the wave by gas-phase pressure variations in phase with the wave slope and viscous dissipation). When these waves grow to a certain amplitude, a bifurcation exists whereby they have the possibility of doubling in wavelength. Bontozoglou and Hanratty argued that this bifurcation is the first step in the evolution of these waves to slugs and that the bifurcation is triggered by a subcritical Kelvin-Helmholtz instability. No experimental evidence is available to support this mechanism. Lin and Hanratty (1987b) reported on visual observations of the initiation of slugs in horizontal 0.051-m and 0.095-m pipelines. The mixer for the air and water at the inlet was a simple tee in which the liquid moved along the run. At gas superficial velocities (defined as the gas volumetric flow divided by the cross section of the empty pipe) below 3 m/s, the first slugs were observed to originate far downstream from the entry. The formation occurred so rapidly that the details could not be documented. With increasing liquid flow rate, the location of the transition was observed to move closer to the inlet. At large enough liquid flow rates, several slugs existed in the pipe at a given time and the slugs originated in the mixing section where the process could not be observed. At superficial gas velocities above 3 m/s, slugs were reported to form as the result of the coalescence of Kelvin-Helmholtz waves. This study uses both photographic and instrumental methods to obtain information about how slugs evolve. Results are given for air/water flow at atmospheric pressure in a 0.095-m hor

Carbon dioxide is a green alternative for mineral acids (e.g., sulphuric acid) in protein precipitation. The precipitation using a gaseous precipitant differs from the conventional precipitation in the way and the rate at which the precipitant can be applied to the aqueous solution. In this paper, the consequences of using carbon dioxide were investigated for the precipitation of the milk protein casein. Product properties, such as particle size, solids content and calcium release were investigated in a batch system at various mixing conditions and gas addition rates. In addition, mass transfer coefficients were determined from pH response data.

The volatilization of stibnite (Sb 2 S 3 ) in nitrogen and mixtures of nitrogen-oxygen was investigated in the temperature range 973 K to 1423 K (700°C to 1150°C). The overall volatilization reaction study was carried out using a thermogravimetric analysis technique under various gas flow rates. The results indicated that in an inert atmosphere, stibnite can be volatilized most efficiently as Sb 2 S 3 (g) with a linear rate up to about 1173 K (900°C). At temperatures above 1223 K (950°C), stibnite decomposes to antimony and sulfur gas, impairing the antimony volatilization. For linear behavior in nitrogen gas, kinetic constants were determined, and an activation energy of 134 kJ/mol was calculated for the volatilization reaction. However, in the presence of oxygen, antimony can be volatilized efficiently as valentinite (Sb 2 O 3 ) at low oxygen concentrations (approximately 1 to 5 pct) at approximately 1173 K to 1223 K (900°C to 950°C); otherwise, at higher partial pressures of oxygen, the volatilization of antimony is limited by the formation of nonvolatile cervantite (SbO 2 ). In highly oxidizing atmospheres, a high vaporization of antimony could be achieved only at temperatures higher than 1423 K (1150°C) where cervantite becomes unstable and decomposes into SbO(g) and 0.5O 2 (g).

The removal rate of carbon from amorphous graphite-tungsten composite during cleaning in oxygen plasma was studied. The composite was prepared by sputter deposition from C and WC-targets in Ar atmosphere. A total thickness of deposited layer was about 1 μm. The samples were treated in a weakly ionized highly dissociated oxygen plasma created in a microwave discharge at a power of 1 kW. The gas flow was 13 slh and the pressure was 200 Pa. The temperature of the samples during treatment was about 580°C. After plasma treatment the samples were analyzed by AES (Auger electron spectroscopy) depth profiling, XPS (X-ray photoelectron spectroscopy), SEM (Scanning electron microscopy) and AFM (Atomic force microscopy). It was found that during the plasma treatment selective etching of the composite occurred. Carbon was preferentially removed from the composite. XPS results have shown that during the plasma treatment a layer of WO 3 was growing on the surface. After about 15 min, carbon was completely removed from the deposited composite layer.

Generation and features of the radio frequency (rf) hollow cathode discharge (HCD) and its transition into the hollow cathode arc (HCA) are described. Rf linear hollow cathodes for generation of plasma over large areas and suitable for further scale-up are presented. Examples of surface processing and coating by PVD, both by HCD and HCA, are given. The hybrid reactor, combining hollow cathode and microwave plasmas, integrates features of both and provides more options to control plasma characteristics and consequently properties of deposited films. The rf hollow cathodes can be operated in both, PVD and PE CVD regimes, depending on process parameters. These regimes can even be combined within one process. New concepts of fused hollow cathode (FHC), microwave antenna (MWA) and Hybrid hollow electrode activated discharge (H-HEAD) cold atmospheric plasma sources are introduced. The FHC with its modular concept can be used for gas conversion, cleaning and for surface treatment of temperature-sensitive materials at ambient atmosphere. The H-HEAD cold atmospheric plasma source, capable of generating plasma plumes more than 15 cm long, enables treatment of 3-d and complex geometry objects even at low gas flows.