Gas Flow Pressure Research Articles

Conveying characteristics and resistance characteristics in dense phase pneumatic conveying of rice husk and blendings of rice husk and coal at high pressure

Dense phase pneumatic conveying experiment of rice husk powder and blendings of rice husk and coal was carried out at the pressure of up to 4.0MPa in an experimental facility. Effects of operation conditions and mixing ratios of rice husk and coal on conveying behaviours were investigated. Results indicated that superficial gas velocity increased as total conveying differential pressure and supplemental gas flow rate increased, respectively. Solid loading ratio increased with increasing total conveying differential pressure, but decreased with increasing supplemental gas flow rate. Under the same operation conditions, superficial gas velocity decreased with the increasing in content of coal in blendings, while solid loading ratio increased gradually. The flow stability analysis results indicated that conveyings of blendings were more stable than that of pure rice husk, the flow stability was improved by adding coal. Characteristics of pressure drops in horizontal pipe, vertical pipe, horizontal bend and vertical bend were presented. Empirical correlations of additional pressure drop coefficients and pressure drops of vertical pipe, horizontal pipe, vertical bend and horizontal bend were proposed.

Preparation and Oxygen Permeation of La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) Perovskite-Type Membranes: Experimental Study and Mathematical Modeling

La0.6Sr0.4Co0.2Fe0.8O3−δ nanopowder, synthesized via an autocombustion technique, was pressed into disk-shaped membranes. Results of permeation experiments revealed that oxygen permeation flux increases as temperature, feed side oxygen partial pressure, and feed and sweep gas flow rates increase, while it decreases with membrane thickness and permeate side oxygen partial pressure. A Nernst–Planck based mathematical model, including surface exchange kinetics and bulk diffusion, was developed to predict oxygen permeation flux. Considering nonelementary surface reactions and introducing system hydrodynamics into the model resulted in an excellent agreement (RMSD = 0.0344, AAD = 0.0274 and R2 = 0.9960) between predicted and measured fluxes. Feed side surface exchange reactions, bulk diffusion, and permeate side surface exchange reaction resistances are in the range of Rex′ = 7 × 103 to 9 × 106, Rdiff = 1 × 105 to 2 × 107, and Rex″ = 1 × 104 to 2 × 107 (s/m), respectively. The permeation rate-limiting step was determined using the membrane dimensionless characteristic thickness.

디스플레이용 외장패널의 가스사출공정 개발

Gas Assisted Injection Molding is a relatively new low-pressure injection molding technique that provides benefits such as reduced part warpage, excellent surface quality without shrink marks, greater design flexibility, etc. In the gas assisted injection molding process, the injected pressurized nitrogen gas flows through designed gas channels and forms hollow sections within the part. However, due to the characteristics of the gas, the design of the gas channels which are the paths for the injected gas is important in order to avoid defects such as gas blowout, fingering, etc. Therefore, in this study, the gas channel design for gas assisted injection molding of exterior display panels was conducted by examining the results of three CAE analyses. The designed gas channel was verified by conducting tryouts using a 450 ton injection molding machine with 3-stage pressure controlled gas kit. In addition, the hollow shapes which were formed by the gas with the installed gas channels were examined by examining the cross sections of the prototypes that were produced. As a result, it was found that exterior display panels can be produced without any defect by applying the gas assisted injection molding technique.

Experimental study on the performance of sand control screens for gas wells

Based on the sand control mechanism, similarity criterion and factors affecting the stability of borehole plastic region, a large-scale laboratory test apparatus for simulating the performance of sand control screens for gas wells was developed. A series of sand control simulation experiments were performed. Based on the particle size analysis of formation sand and geological conditions, parameters of sand control screen, such as sand retention efficiency, were investigated. By simulating formation conditions, such as pressure gradient and gas flow rate, the performance of several types of screens, including slotted screen, wire wrapped screen and premium composite screen that are commonly used in oilfield, was evaluated. Experimental results were discussed and premium composite screen was found to be most efficient for sand control among all the tested screens. This study provides a sound experimental method for evaluating the performance of sand control screens for gas wells.

Numeral Simulation on the Venting Explosion Process of Methane and Propane Gas in Closed Cylindrical Vessel

Abstract The mathematical model of the pressure field in the vented explosion process in closed cylindrical vessel containing methane and ethane was built based on the soft-ware fluent. The characteristics of pressure development, flame propagation, gas flow and flammable gas concentration change have been studied in the process of bursting disc open to pressure completely discharge. The results show that the development and change of vessel pressure exhibit different characteristics in the venting explosion process of different flammable gas, and vessel pressure will take on a double-peak phenomenon during the explosion process of highly reactive gas. The turbulent flow produced in the process of venting explosion will elongate the flame along the vessel surface near vent and enhance the burning rate.

Optimisation of p-doped μc-Si:H Emitter Layers in Crystalline-amorphous Silicon Heterojunction Solar Cells

Heterojunction silicon wafer solar cells, using a microcrystalline silicon (μc-Si:H) thin-film emitter and a very thin intrinsic amorphous silicon (a-Si:H) passivation layer between the crystalline silicon wafer and the emitter layer, have been reported to exhibit stable performance and high efficiency. Desired properties for the emitter layer include wide bandgap, low surface and interface recombination, and good doping efficiency. In this study, we report on the thin-film properties of p-doped μc-Si:H emitter layers deposited using RF (13.56MHz) PECVD, at different SiH4/H2 gas flow ratios, pressures, and temperatures at the same RF power. Trends relating deposition conditions to relevant film characteristics such as thickness, crystalline fraction and conductivity are discussed. Finally, device relevant symmetrical p+/i/c-Si/i/p+ heterojunction lifetime test structures are investigated, using the optimised parameters for p-doped μc-Si:H layers (discussed in this paper) and for intrinsic a-Si:H layers (discussed in a companion paper [1]). These exhibit promising effective lifetimes of up to 2.4ms at an injection level of 1015cm-3.

Optimisation of Intrinsic a-Si:H Passivation Layers in Crystalline-amorphous Silicon Heterojunction Solar Cells

Heterojunction silicon wafer solar cells using an intrinsic amorphous silicon (a-Si:H) thin-film passivation layer between the crystalline c-Si substrate and the thin-film emitter layer have proven to be a viable device structure for high efficiency. While microcrystalline μc-Si:H is a good candidate for the emitter layer due to its high doping efficiency, intrinsic a-Si:H with its low interfacial defect density, high optical bandgap and good passivation ability makes it the ideal buffer layer to passivate the crystalline silicon interface. In this study, we report the film properties of intrinsic a-Si:H passivation layers deposited using RF (13.56MHz) PECVD, at different SiH4/H2 gas flow ratios, pressures and temperatures. Trends relating deposition conditions to relevant film characteristics, such as thickness, hydrogen bonding, optical bandgap, and effective carrier lifetime of the samples are discussed. Finally, symmetrical p+/i/c-Si wafer/i/p+ heterojunction lifetime test structures, using 20nm thick p-doped μc-Si:H emitter layers and 10nm thick intrinsic a-Si:H layers, were made using the optimised parameters for intrinsic a-Si:H layers (discussed in this paper) and for p-doped μc-Si:H layers (discussed in a companion paper [1]). These yield an effective lifetime of 2.4ms at an injection level of 1015cm-3, and an implied Voc of 730mV.

A Two-Stage Wood Chip-Based Biofilter System to Mitigate Odors from a Deep-Pit Swine Building

A mobile biofilter testing laboratory was developed where two-stage biofilters filled with western cedar and hardwood chips were examined to treat odor emissions from a deep-pit swine finishing facility in central Iowa. An automatically controlled water supply system was tested and used to control media moisture content. Odor concentrations from theinlet and biofilter treatments, gas flow pressure drop, leachate pH and ammonia concentration, and water consumption were monitored.Results indicate that the water supply system tested in this study can keep wood chip media at a high and stablemoisture content of 72% 3% (western cedar) and 62% 3% (hardwood)with a 6.4 L/m3-day water supply. Western cedar (WC) chips achieved an average reduction efficiency of 51%, 83%, and 41% for odor, H2S, and NH3, respectively, when keeping the WC moisture content at 72% and the empty bed residence time (EBRT) between 3.7 and 5.5 s. A linear relationship between media unit pressure drop and unit airflow rate was observed with two-stage biofilters having an advantage in potentially reducing media compaction.Leachate pH and NH3 concentration were measured with pH levels in the 7.2 to 7.9 range with the NH3 concentration in the 198 to 1300 mg/L as N range.The effects of three different levels of media moisture content shows that proper moisture content is a key factor for the success of wood chip biofilters, but is not a substitute for inadequate EBRT.

고온열을 이용한 고온수증기전기분해장치(HTSE)에 의한 수소생산 특성에 관한 전산유체해석적 연구

The characteristics for hydrogen production and the thermochemical properties of high temperature steam electrolysis(HTSE) device have been numerically analyzed in a two-dimension, steady-state with using the COMSOL . The main parameters for the calculation are applied voltage, ASR(Area-specific Resistance), temperature and pressure of the inlet gas flow. The results showed that thermal-neutral voltage was 1.2454 V and rather than the cell temperature increases or decreases with increasing applied voltage by thermal-neutral voltage starting this voltage the temperature in high voltage tended to rise and temperature in the low voltage tended to fall. And with, increasing the values of ASR, temperature inside the cell and the hydrogen production rate were decreased.

Determination of the volatiles from tobacco by capillary gas chromatography with atomic emission detection and mass spectrometry

A new gas chromatograph-atomic emission detector (GC-AED) coupled with Deans switching technique for analyzing volatiles from tobaccos were developed. The detector operating parameters (reagent gas pressure and make-up gas flow rate) were optimized. The detection limits for the elements carbon (193 nm), hydrogen (486 nm) and oxygen (171 nm) ranged 0.05-0.2, 0.05-0.3 and 1-11 ng, respectively, depending on the compound. The sensitivity and linearity for the elements carbon (193 nm), hydrogen (486 nm) and oxygen (171 nm) decreased in the order O>H>C. Calibration curves were obtained by plotting peak area versus concentration, and the correlation coefficients relating to linearity were at least 0.9359. Elemental response factors measured on these channels, relative to the carbon 193-nm channel, were hydrogen, 0.38-0.48 (mean %RSD=5.64), and oxygen, 0.085-0.128 (mean %RSD=14.9). The evaluation was also done for the new technique and for an established GC-MS technique for the same real samples. The results of GC-AED and GC-MS showed that there was a relatively good agreement between the two sets of data.

Etching characteristics and mechanisms of SiC thin films in inductively-coupled HBr-Ar, N2, O2 plasmas

Etch characteristics and mechanisms of SiC thin films in HBr-Ar, HBr-N2, and HBr-O2 inductively-coupled plasmas were studied using a combination of experimental and modeling methods. The etch rates of SiC thin films were measured as functions of the additive gas fraction in the range of 0–100% for Ar, N2, and O2 at a fixed gas pressure (6 mTorr), input power (700 W), bias power (200 W), and total gas flow rate (40 sccm). The plasma chemistry was analyzed using Langmuir probe diagnostics and a global (zero-dimensional) plasma model. The good agreement between the behaviors of the SiC etch rate and the H atom flux could suggest that a chemical etch pathway is rather controlled by the gasification of carbon through the CHx or CHxBry compounds.

Computational Analysis and Studies on Differential Ejector

Studies on differential ejector configuration have been carried out with a view to obtain the optimal entrainment of low pressure gas flow by injecting the motive gas at an appropriate pressure and angle of injection. The length of mixing has been kept constant in one case and varied in another to get results for optimal angle of ejection (between 0 to 90 degrees) for varying mass flow rates between 0.02kg/s and 0.08kg/s, stagnation pressures between 200kPa to 2500kPa and conduit diameter being 50mm. The predictions made are validated employing a versatile code Fluent in 2-d, viscous, turbulent flow formulation. Since the flow is supersonic, compressible form of SIMPLE algorithm is used along with a first order upwinding scheme for correctly predicting the properties inside the flow domain. Various curves have been plotted depicting variation of Mach number with angle of ejection and Mach number with mass flow rate for various pressures and angles of ejection.

Development of tensile stress near a wellbore in radial porous media flows of a high pressure gas

The development of tensile stress near a wellbore in steady radial porous media flows is examined in detail, in particular for high pressure gas flows. It is shown that poroelasticity induced radial stress is always tensile for any pore pressure distribution. This induced tensile stress reaches a maximum value at the interior point where the local pore pressure equals the average pore pressure. It is also shown that no effective tensile stress can develop in Darcy flows of a liquid, while effective tensile stress can appear in Darcy flows of a gas when the drawdown pressure is large. The smallest flow-rate for the appearance of effective tensile stress occurs when gas acceleration effects become important in high pressure, high speed gas flows. For the flow beyond the critical condition for the occurrence of effective tensile stress, the tensile stress level depends strongly on the gas acceleration.

Tritium In-Bed Accountability for a Passively Cooled, Electrically Heated Hydride (PACE) Bed

A PAssively Cooled, Electrically heated hydride (PACE) Bed has been deployed into tritium service in the Savannah River Site (SRS) Tritium Facilities. The bed design, absorption and desorption performance, and cold (non-radioactive) in-bed accountability (IBA) results have been reported previously. Six PACE Beds were fitted with instrumentation to perform the steady-state, flowing gas calorimetric inventory method. An IBA inventory calibration curve, flowing gas temperature rise (ΔT) versus simulated or actual tritium loading, was generated for each bed. Results for non-radioactive (“cold”) tests using the internal electric heaters and tritium calibration results are presented.Changes in vacuum jacket pressure significantly impact measured IBA ΔT values. Higher jacket pressures produce lower IBA ΔT values which underestimate bed tritium inventories. The exhaust pressure of the IBA gas flow through the bed’s U-tube has little influence on measured IBA ΔT values, but larger gas flows reduce the time to reach steady-state conditions and produce smaller tritium measurement uncertainties.

Experimental and theoretical investigation of thermoacoustic oscillations in natural gas metering stations

In natural gas flow metering and pressure regulation stations flowmeters, heat exchangers and control valves are usually connected in series. Especially in the case of two or more measuring bars sometimes at minor flow rates untypical pipe vibration together with flow metering faults are observed. Based on field investigations the dependencies between the pipe vibration level, the gas pulsation inside the pipe and the operating conditions of the heat exchanger are analysed. It turns out that with increasing heat flow rates into the natural gas the pulsation and hence the metering faults as well as the pipe vibrations are amplified.In order to understand the physical dependencies of this phenomenon besides experiment a theoretical study is performed. The origin of the vibration turns out to be a thermoacoustic instability. According to the Rayleigh criterion gas pulsations are amplified if heat is given to the gas at the moment of greatest condensation. Based on detailed theoretical investigations by means of the method of characteristics using a Rijke tube model the physical dependencies are analysed. Finally potential solutions to avoid this vibration problem at natural gas metering stations are introduced.

Experimental study of the effect of process parameters on plasma-enhanced chemical vapour deposition of silicon nitride film

The effect of plasma-enhanced chemical vapour deposition parameters on refractive index and deposition rate of silicon nitride films is investigated. Usually, this kind of study is performed in a laboratory system. In the present work, a horizontal batch system for the simultaneous coating of 100 silicon wafers is used. Using a gas mixture of silane and ammonia as the reactant-gas sources, the effects of the gas flow rate ratio ( R = NH3/SiH4 with the total flow rate constant), pressure, power and temperature on the refractive index and deposition rate were studied and the experimental results are presented and discussed.

Preparation and characterization of PES and PSU membrane humidifiers

Polysulfone (PSU) and polyethersulfone (PES) porous membranes; and mixed polymer with nanoparticles TiO 2, were prepared for air humidification. The mechanical properties and morphology of these membranes were studied by Tensile tester and SEM/EDX. The effects of membrane composition and operating factors on humidifier performance were investigated. The results revealed that the membrane composition and its structure have significant effect on humidification. The porous membranes with finger type cavities had higher humidification performance but lower mechanical properties. Water flux of the membranes was about 0.16–0.2 L/h m 2 at 25 °C. Furthermore, adding 0.1 wt% TiO 2 nanoparticles to casting solution enhanced the humidification. Water flux of the membranes with TiO 2 nanoparticles was about 0.18–0.22 L/h m 2 at 25 °C. Relative humidity of outlet gas was decreased by increasing the gas flow rate and pressure. An increase in system temperature caused the relative humidity of the outlet gas to decrease.

Nano-lead particle synthesis from waste cathode ray-tube funnel glass

Waste cathode ray-tube (CRT) funnel glass is classified as hazardous waste since it contains high amount of lead. In the present study, a novel process for lead nanopowder synthesis from this type of glass was developed by combining vacuum carbon–thermal reduction and inert-gas consolidation procedures. The key trait of the process was to evaporate lead out of the glass to obtain harmless glass powder and synchronously produce lead nanoparticles. In the synthesis process, lead oxide in the funnel glass was firstly reduced to elemental lead, and evaporated rapidly in vacuum circumstance, then quenched and formed nano-size particles on the surface of the cooling device. Experimental results showed that temperature, pressure and argon gas flow rate were the major parameters controlling lead evaporation ratio and the morphology of lead nanoparticles. The maximum lead evaporation ratio was 96.8% and particles of 4–34 nm were successfully obtained by controlling the temperature, holding time, process pressure, argon gas flow rate at 1000 °C, 2–4 h, 500–2000 Pa, 50–200 ml/min, respectively. Toxicity characteristic leaching procedure (TCLP) results showed that lead leaching from the residue glass met the USEPA threshold. Accordingly, this study developed a practical and environmental-friendly process for detoxification and reclamation of waste lead-containing glass.

CFD simulation of the two-phase flow for a falling film microreactor

Falling film microreactors, which provide very high specific interfacial area, have become a promising solution to the fast and strongly exothermic/endothermic gas–liquid reaction systems. A computational fluid dynamic simulation of the two-phase flow for a falling film microreactor is presented using the volume of fluid (VOF) model. The hydrodynamic characteristics, from both 2-D and 3-D simulations, including liquid film thickness, velocity, pressure and shear stress profiles, are analyzed. 2-D simulation is adopted for the study of the relationship of liquid flow rate and film thickness, as well as the effects of gas flow rate, surface tension, liquid viscosity and pressure difference on the liquid flow rate. 3-D simulation is necessary to provide the comprehensive flow profiles. Although the system is in the laminar flow regime, the liquid film features a wavy structure and the velocity profiles are complex.

Development of Test Method for Measuring Sintering Temperature of Mould Fluxes

Excessive sintering of mould fluxes can readily cause defects and sticker breakouts in continuously cast strands. Studying the sintering property is important to minimize problems related to sintering arising from the use of mould fluxes in continuous casting. An effective method of measuring the apparent sintering temperature has been developed in this study. The method is based on monitoring the formation of cavities caused by melting of samples. For monitoring, the differential pressure of an inert gas flow was measured through a set volume of sample (mould flux A) held in a furnace tube. The apparent sintering temperature was defined in this test to determine sintering process. The sintering properties of fluxes with various contents of carbon black were examined along with identification of mineralogical phases and the nature of the sinter for samples of mould flux A held for one hour at different temperatures. The experimental results indicated that the apparent sintering temperature (AST) was a useful parameter to assess the threat of problems related to sinter.