Showing papers on "Volumetric flow rate published in 1987"

Fluid flow through rock joints: The effect of surface roughness

Abstract: Fluid flow through rock joints is commonly described by the parallel plate model where the volume flow rate varies as the cube of the joint aperture. However, deviations from this model are expected because real joint surfaces are rough and contact each other at discrete points. To examine this problem further, a computer simulation of flow between rough surfaces was done. Realistic rough surfaces were generated numerically using a fractal model of surface topography. Pairs of these surfaces were placed together to form a “joint” with a random aperture distribution. Reynolds equation, which describes laminar flow between slightly nonplanar and nonparallel surfaces, was solved on the two-dimensional aperture mesh by the finite-difference method. The solution is the local volume flow rate through the joint. This solution was used directly in the cubic law to get the so-called “hydraulic aperture.” For various surface roughnesses (fractal dimensions) the hydraulic aperture was compared to the mean separation of the surfaces. At large separations the surface topography has little effect. At small separations the flow is tortuous, tending to be channeled through high-aperture regions. The parameter most affecting fluid flow through rough joints is the ratio of the mean separation between the surfaces to the root-mean-square surface height. This parameter describes the distance the surface asperities protrude into the fluid and accounts for most of the disagreement with the parallel plate model. Variations in the fractal dimension produce only a second-order effect on the fluid flow. For the range of joint closures expected during elastic deformation these results show that the actual flow rate between rough surfaces is about 70–90% of that predicted by the parallel plate model.

Fluid infusion flow control system

Abstract: Flow of fluid from primary and secondary reservoirs is induced along parallel flow paths to a common infusion device under gravity or pump inducing modes, respectively. The fluid delivered to the infusion device is monitored by a flow meter to measure its actual flow rate and adjust flow along the parallel flow paths to maintain a substantially constant selected flow rate by means of a programmed control system through which selection of the flow inducing mode and the reservoir may be effected.

Effect of air flow rate on carrot drying

Abstract: The influence of air flow rate on the kinetics of drying 10x10x10 mm carrot cubes is presented. For this geometry kinetic equations are available, for the first falling rate drying period. Drying air flows of 1000, 2000, 2500, 3000, 4000, 5000, 6000, 8000 and 9000 kg/m 2 h were employed. It was found that for flow rates above 6000 kg/m2 h the value of D/r2 remains almost constant, thus indicating that when the air flow rate is higher it has no influence on the drying rate. The influence of air flow rate on carrot drying has been determined, hence allowing optimal flow rate calculation under economic constrictions.

Drop volume measurement system

Abstract: Apparatus and method for measuring the volume of a drop, and with a series of drops the volumetric flow rate of a fluid utilizing a vertically oriented, transparent drop chamber through which the fluid is directed in drop form. A plurality of drop sensors positioned adjacent to the drop chamber in vertically spaced relation to each other emit signals in response to the detection of the entrance and exit of each drop to and from separate sensor fields preferably established by light emitting sources. The drop sensors are connected to control circuitry incorporating an electronic processor programmed to determine volumetric flow rate in response to drop dimension and drop rate signals received from the drop sensors. The drop size in terms of the vertical dimension of each drop in the direction of gravity flow through the drop chamber is determined by measuring the time it takes a drop to pass through each and both of the two sensor fields. Timers used for this purpose are triggered by the aforesaid sensor signals. The volume of each drop is electronically calculated as a function of the drop vertical dimension, and drop volume and drop rate are multiplied to determine volumetric flow rate.

Physical modeling of liquid/liquid mass transfer in gas stirred ladles

Abstract: Several of the metallurgical reactions occurring in gas stirred steel ladles are controlled by liquid phase mass transfer between the metal and slag. In order to calculate the rate of these reactions, information about the two phase mass transfer parameter is necessary. The mass transfer between two immiscible liquids, oil and water simulating slag and steel, respectively, was measured in a scale model of a ladle. The mass transferred species was thymol which has an equilibrium partition ratio between oil and water similar to that for sulfur between slag and metal. The mass transfer rate was measured as a function of gas flow rate, tuyere position and size, method of injection, oil viscosity, and oil/water volume ratio. In addition, mixing times in the presence of the oil layer and mass transfer coefficient for the dissolution of solid benzoic acid rods were measured. The results show that there are three gas flow rate regimes in which the dependence of mass transfer on gas flow rate is different. At a critical gas flow rate, the oil layer breaks into droplets which are entrained into the water, resulting in an increase in the two phase interfacial area. This critical gas flow rate was found to be a function of tuyere position, oil volume, densities of two phases, and interfacial tension. Two phase mass transfer for a lance and a tuyere was found to be the same for the same stirring energy in low energy regions regardless of lance depth. Mass transfer is faster for a center tuyere as compared to an offcenter tuyere, but mixing times are smaller for the offcenter tuyere. From the results obtained, the optimum stirring conditions for metallurgical reactions are qualitatively discussed.

Gas lift optimization

Abstract: Optimizing the production of well fluids from a well by controlling the injection gas flow rate. Determining the time delay for various gas flow rates to produce a constant liquid flow rate and determining the relationship between the injection gas flow rate and the amount of liquids produced and calculating the required injection gas flow rate to produce a selected amount of liquids. Thereafter the gas flow rate is adjusted considering the determined time delays to reach the required injection gas flow rate without injecting more gas than is needed.

Method and system for vapor extraction from gases

Abstract: Vapor phase waste species are removed from effluent gas streams using a plasma extraction reactor comprising a pair of parallel, spaced-apart electrodes. The electrodes are driven under conditions, usually at radio frequency, to induce a glow discharge in the waste species, and the excited species are deposited directly on the electrode surface. By providing a very high ratio of electrode area to reactor volume and waste gas volumetric flow rate, substantially complete removal of the waste species can be effected. The system is particularly useful in removing contaminant species discharged from semiconductor processing operations, such as chemical vapor deposition and plasma etching. The method and system are particularly advantageous in that the vapor phase waste products are converted to a solid phase deposited directly on the electrodes which may then be disposed of.

Monolithic pressure-flow sensor

Abstract: A new silicon-based monolithic pressure-flow sensor has been developed. Its operation is based on the piezoresistive effect for pressure sensing and heat transfer for flow sensing. The sensor chip has a thermal isolation structure that is made of an oxidized porous silicon membrane. This structure thermally isolates the heating element located on the membrane from the rim of the chip. The sensor, in which the chip was mounted on a wall of an acrylate plastic pipe, was designed for biomedical applications. Measurements were made at pressures of 0-300 mmHg, water flow rates of 0-7 1/min, and fluid temperatures of 25-45°C. The temperature difference between the heating element and the fluid temperature sensing element was kept at 5°C. The sensor showed a pressure sensitivity of 1.32 µV/mmHg for 1-mA current supplied, a nonlinearity of 0.5 %F.S. for pressure sensing, an accuracy of ±10 %F.S. for flow sensing, and 90-percent response time of below 100 ms for flow sensing. The sensor was applied to the simultaneous measurements of pressure and flow rate in pulsedflow experimental systems.

Low flow rate-low pressure atomizer device

Abstract: A low flow rate-low pressure atomizer device is disclosed which is so dimensioned and operated as to accelerate a gas to substantially sonic velocity and cause it to break up a cleaning liquid into small droplets and accelerate these droplets to at least half the velocity of said gas to create shear stress at a surface closely adjacent the exit end of said device, thereby to remove contaminants or the like from said surface.

Upwelling in the liquid region surrounding the keyhole in penetration welding with a laser

Abstract: In penetration welding with a laser, the pressure in the keyhole is in excess at atmospheric pressure. A pressure gradient related to this is produced in the liquid region surrounding it, with the result that there is a flow parallel to the axis of the laser. The velocity of this flow is found as a function of the material constants, and the volume flow rate calculated. From this it is possible to construct an estimate of the elevation or depression of the surface of the weld. the shape of the surface cross section is discussed, and some deductions made about the pressure distribution in the liquid metal.

Modelling and characterization of an airlift-loop bioreactor

Abstract: An airlift-loop reactor is a bioreactor for aerobic biotechnological processes. The special feature of the ALR is the recirculation of the liquid through a downcomer connecting the top and the bottom of the main bubbling section. Due to the high circulation-flow rate, efficient mixing and oxygen transfer is combined with a controlled liquid flow in the absence of mechanical agitators. Liquid velocities and gas hold-ups in an external-loop airlift reactor (ALR) on different scales were modelled on the basis of a simple pressure balance. The model is adapted for non-isobaric conditions and takes into account nonuniform flow profiles and gas hold-up distributions across the duct. The friction coefficient together with the reactor dimensions are input parameters. It has been shown that the friction coefficient can be obtained from simple one-phase flow calculations based on known data of the seperate reactor parts. The model predicts liquid velocities and local gas hold-ups in an ALR to within 10% and can be applied easily to an internal loop reactor. Mixing in the individual sections of the ALR is determined by a newly developed parameter estimation procedure which has proven to be reliable for the estimation of axial dispersion coefficients in the individual sections of the ALR. From the results it can be concluded, that in an ALR the liquid flow behaves like plug-flow with superimposed dispersion except for the topsection for which it is not reasonable to assume plug-flow. The mixing results simplified the modelling of oxygen transfer in the ALR as it appeared not to be necessary to incorporate the dispersion contribution Into the oxygen model. The non-isobaric plug-flow model, presented in this thesis, predicts dynamic and stationary dissolved oxygen concentration (DOC) profiles in large-scale ALRs and has been applied also to estimate the volumetric oxygen transfer coefficient, k 1 a, in the pertinent ALR. Comparison with the results on the basis of a simple isobaric stirred-tank-reactor model demonstrates, that such a model yields conservative values though for the present situation the underestimation did not exceed a value of 10% relative to the plug-flow model. Therefore, due to its simplicity, it is recommended to use the stirred tank model for a rapid characterization of the overall aeration capacity of laboratory scale and pilot-scale ALRs. Oxygen depletion of the gas phase, even during a fermentation, appeared to be very limited and was fairly well predicted by the plug-flow model. For this reason an ALR is a very suitable reactor for aerobic processes having a high oxygen demand. If necessary, the aeration capacity of the ALR can be enhanced by injection of a small amount of gas at the entrance of the downflow region. This phenomenom is also accurately predicted by the plug-flow model. In the present ALR the aeration capacity of the air-sparger region did not significantly differ from the main aeration process in the upflow region due to its special geometry. The intermediate flow region between the ALR and the bubble-column (BC) flow regime was investigated by gradually closing a butterfly valve at the bottom of the downcomer. When the valve is further shut and thus the friction is enhanced, the liquid velocity will be reduced thereby enlarging the gas hold-up. The maximum value for the gas hold-up is obtained when the ALR is operated as a BC. In the transition flow regime between ALR and BC flow, the liquid velocity was found to be a simple power law function of the gas flow rate. The coefficients of the power law depend on the flow characteristics in the reactor. In the transition flow regime the hydrodynamic calculations based on the plug-flow behaviour of an ALR are only valid up to a certain defined value of the total gas-liquid flow rate. For greater values, the ALR type of flow will change Into a BC type of flow. A simple criterium qualifies the distinction between both flow patterns, determined by the superficial liquid velocity and the liquid circulation velocity. The transition of ALR to BC flow coincides with the decrease of the Bodenstein number which also indicates a less established plug flow. As the dispersion coefficient at a constant gas-flow rate, remained constant for as well the ALR, the BC and the transition flow, the decreased Bodenstein number in the BC-type of flow is mainly attributed to the decreased convective transport as the liquid circulation is impeded. The number of circulations required to achieve complete mixing diminshes when the liquid circulation is impeded and appeared to be proportional to the Bodenstein number. In the transition flow regime, the volumetric oxygen transfer coefficient was estimated by both the stirred-tank model and the plug-flow model. The stirred-tank model yielded reliable results for the entire range of operation while the plug-flow model only appeared to be appropiate for the ALR operation mode. The volumetric oxygen transfer coefficient was found to increase for the BC operation mode and appeared to be a power law function of the ratio of the superficial liquid and gas velocity and the Bodenstein number. Addition of immobilized biocatalysts to the ALR, in our case simulated by neutral buoyant particles with diameters ranging from 2.4-2.7 am, significantly reduces the liquid velocity and the gas hold-up in an ALR. The decrease in liquid velocity is attributed to the decrease in gas hold-up and an increased friction in the ALR. The gas hold-up is reduced mainly because the presence of the particles increases the collision frequency of the air bubbles thereby increasing coalescence due to the diminished flowed area available for the air-water mixture. In comparison to a gas-liquid flow, axial dispersion in the three-phase flow is reduced as the presence of the particles damps the small eddies which are, apart from other mechanisms, responsible for the axial dispersion. Moreover. the increased coalescence also contributes to a decrease in axial dispersion. The presence of the particles negatively influences aeration due to a reduction in the gas-liquid interfacial area as a result of the increased coalescence. The effect of the increase in apparent viscosity in the ALR was not supposed to contribute to the decrease in the aeration process.

Gas holdup and axial dispersion in gas-liquid concurrent bubble column

Abstract: An experimental investigation was carried out to determine the effect of liquid flow on gas holdup and axial dispersion coefficient in a gas-liquid concurrent bubble column 20 cm in diameter, in the ranges of gas and liquid superficial velocities of 0.21-0.87 and 0-1.16ms-1, respectively. Theoretical expressions of the turbulent recirculation flow were developed to account for the effect of liquid flow rate. With increasing liquid upflovv rate, the value of axial dispersion coefficient decreases at relatively small liquid flow rate and turns to increase at large flow rate, whereas the value of gas holdup decreases simply. These phenomena were quantitatively explained by the developed theory, including the effect of column diameter.

Hydrostatic drive system

Abstract: A hydrostatic drive system consists respectively of an adjustable primary and secondary unit which are connected together via a conduit train with impressed pressure. The volume flow of the primary unit is regulated in dependence upon the impressed pressure and the volume flow of the secondary unit as a function of the speed. To avoid pronounced dropping of the impressed pressure the power of the secondary unit is limited. For this purpose a circuit is provided in which the volume flows of the primary and secondary units are compared. The power limitation intervenes when the volume flow of the secondary unit exceeds the volume flow of the primary unit.

Calibration method for exhaust mass flow measuring system

Abstract: A testing apparatus for sampling the emission content of the source when a portion of the exhaust gas is optionally diluted using clean dry air added near the sample extraction point. A sonic venturi is used to establish a constant mass flow rate from the exhaust system of the engine under test and a subsonic venturi monitors the flow rate of dilution air. Both venturis provide flow rate signals which are substracted to determine the flow rate of the exhaust.

Coating material supply device

Abstract: A coating material supply device in which coating material is pumped out at a predetermined flow rate and supplied at a constant flow rate to a coating machine. The device includes a plurality of double-acting reciprocal pumps, each having an inlet for the coating material supplied from a coating material supply source and an exit for discharging the coating material by the pressure of hydraulic fluid supplied at a constant flow rate from a hydraulic fluid supply source. The exits are connected to coating material selection valves connected in parallel with each other to the coating machine, and connected to switching valves that selectively switch the flow channel for the hydraulic fluid supplied from the hydraulic fluid supply source in response to the switching operation of the coating material selection valves. A flow rate control mechanism for maintaining the flow rate of the hydraulic fluid constant is disposed in the flow channel for the hydraulic fluid, between the hydraulic fluid supply source and the switching valves.

Preparation of silicon nitride films at room temperature using double-tubed coaxial line-type microwave plasma chemical vapor deposition system

Abstract: Silicon nitride films were prepared at room temperature using the double‐tubed coaxial line‐type microwave plasma chemical vapor deposition system. The dependence of film composition and properties on the flow rate of SiH4 gas and on the partial pressure of N2 gas in the deposition chamber has been investigated. A new simple method was suggested and employed to determine the film composition from the refractive index and nitrogen concentration. The flow rate of SiH4 gas was varied between 1 and 10 ml/min. The flow rate of N2 gas was at 50 ml/min and the partial pressures of N2 gas in the deposition chamber were set at 0.015 and 0.0036 Torr by changing the size of the substrate table. With an increasing flow rate of SiH4 gas, the following effects upon the films were obtained: proportional increases in the deposition rate, shifts to lower energy of the absorption edge, decreases in the film density, and decreases in the concentration of N and the N–H bond. Increases in the refractive index, the Si/N ratio,...

Laser-sustained plasmas in forced argon convective flow. I - Experimental studies

Abstract: The results of an experimental investigation of the properties of laser-sustained plasmas in argon at forced convective flow speeds of 0.4-4.5 m/s are reported in this paper. At these speeds, the incident flow rate has a significant effect on the shape, size, and position of the plasma, which in turn affect the power absorption, thermal radiation, and total energy conversion efficiency of the plasma. In addition to the incident flow rate, the focusing geometry, chamber pressure, and laser power were varied as parameters in the experiments. The thermal conversion efficiency was found to range 9-38%, depending on the various parameters.

Power-law fluids in porous media

Abstract: An analysis is presented to describe the parallel flow of power-law fluids within a channel bounded by porous media. It is shown that there is an excess flow above the Darcy's law prediction for the porous medium region adjacent to the channel/ porous medium boundary. This also leads to a higher flow rate in the channel. The excess flow increases with a decreasing value of the power law index, and with increasing permeability. The excess flow is found to reach a maximum at an intermediate value of the dimensionless channel width (=½H/K½and it vanishes in the limit of h→∞and h→0. Experimental evidence is also presented to demonstrate the excess flow. The experimental data are found to be in reasonable agreement with the proposed flow model.

Multiple mode regulator

Abstract: A system for controlling the rate of flow of a fluid dispensed in a fluid coating material dispensing circuit includes a source of a first fluid coating material to be dispensed from the coating material dispensing circuit, a source of a desired first fluid flow rate-related signal, a fluid utilization output, and a fluid flow rate regulator for controlling the flow rate of the first coating fluid at the fluid utilization output in response to the desired first fluid flow rate-related signal. The regulator includes a first fluid flow rate-related signal input port and a separate and distinct second flow rate-related signal input port, an input port for the first fluid, and an output port for the first fluid. The input port for the first fluid is coupled to the source of the first fluid. The output port for the first fluid is coupled to the fluid utilization output. The source of the first fluid flow rate-related signal is coupled to the first fluid flow rate-related signal input port. The source of the first fluid flow rate-related signal is coupled to the separate and distinct second flow rate-related signal input port.

Numerical Simulation of Opposed Flow Flame Spread over a Thermally Thick Solid Fuel

Abstract: The opposed flow flame spread over a thermally thick solid fuel has been modelled by means of the gas phase unsteady two-dimensional balance equations for chemical species and energy coupled to the unsteady two-dimensional energy balance for the solid fuel. Finite gas phase kinetics and solid phase pyrolysis with an Arrhenius form are included. The solution is performed numerically by a semi-implicit finite difference method. The flame structure and the behaviour of the solid phase are predicted and discussed as a function of the opposed flow rate and of the shape of the velocity profile. Qualitative agreement is obtained with previous theoretical studies and with experimental data. The detailed description of the solid phase temperature Geld has allowed to suggest an explanation for the observed decrease of the spread rate when increasing the opposed flow rate.

Thermal transient anemometer

Abstract: A thermal transient anemometer having a thermocouple probe which is utilized to measure the change in temperature over a period of time to provide a measure of fluid flow velocity. The thermocouple probe is located in the fluid flow path and pulsed to heat or cool the probe. The cooling of the heated probe or the heating of the cooled probe from the fluid flow over a period of time is measured to determine the fluid flow velocity. The probe is desired to be locally heated near the tip to increase the efficiency of devices incorporating the probe.

Multiple solutions and flow limitation for steady flow through a collapsible tube held open at the ends

Abstract: Equations for the steady flow of an incompressible, inviscid fluid through a collapsible tube under longitudinal tension are derived by treating the tube longitudinally as a membrane, and taking the collapsibility of the tube into account in an approximate way by replacing in the equation for an axisymmetric membrane a term representing the resistance of the tube to area change by the tube law for collapsible tubes. The flow is assumed to be uniform in a cross-section. A nonlinear differential equation is obtained for the shape of the tube for given values of total pressure p0, flow rate q, longitudinal tension τ and tube law P = P(ρ); where ρ = (A/πR2)½ is the equivalent radius of the tube (A = area of a cross-section, R = radius of the unloaded, then circular tube). The equation can be integrated and analysed in the phase plane. Equilibrium points correspond to uniform flow through cylindrical tubes; saddle points correspond to subcritical flow (S 1) and a higher-order point to critical flow (S = 1). Here S is the speed index, the ratio of the flow speed to the speed of long waves. Near centrepoints there are solutions, that represent area-periodic tubes. For a finite tube, held open at the ends, the steady flow is formulated as a two-point boundary-value problem. On the basis of numerical calculations, and a bifurcation analysis using the method of Lyapunov–Schmidt, the existence and multiplicity of the solutions of this problem are discussed and the process of flow limitation studied. For negative total pressures two collapsed solutions are found that disappear at the flow-limitation value of the flow rate. For positive total pressures a distinction is made between subcritical, critical and supercritical total pressures. In all these cases there is a multiplicity, proportional to the ratio of the tube length to [Lscr ]1(0), the wavelength of the collapsed periodic solution for vanishing flow rate, and having maximum radius ρ = 1. For subcritical total pressures increase of the flow rate leads to a gradual loss of all solutions in higher-order flow limitations until final flow limitation occurs by the mergence of two collapsed solutions. For supercritical total pressures increase of the flow rate also leads to a gradual loss of all solutions in higher-order flow limitations in a process which now also depends upon the ratio of the tube length to the wavelength L of periodic solutions with vanishing amplitude and ρ ≡ 1.

Physical modeling of gas/liquid mass transfer in a gas stirred ladle

Abstract: The absorption of gas through the plume eye and of an injected gas in a steelmaking ladle process was investigated, using a physical model of CO2 absorption into a NaOH solution. The results show that the inert gas escaping through the plume eye is ineffective in protecting the bath from the atmosphere, and placing an oil layer (simulated slag) decreases the absorption rate significantly. Increasing the flow rate of the inert gas not only exposes more of the liquid surface to the CO2 atmosphere, but also increases the mass transfer coefficient at the surface. The overall mass transfer between an injected CO2 gas and NaOH solution includes the mass transfer through the surface of the bath as well as the mass transfer in the bubble dispersion zone. The difference between the mass transfer in the bubble dispersion zone and the overall mass transfer was found to be significant for relatively low gas flow rates. The mass transfer coefficient of CO2 in the bubble dispersion zone was estimated using available information regarding the bubble size and velocity. Mass transfer coefficient estimated for the constant bubble frequency regime shows a dependence on gas flow rate. However, if a constant characteristic size of bubbles is assumed as an alternative approach, the mass transfer coefficient is independent of the gas flow rate.

Influence of deposition conditions on the properties of silicon nitride films prepared by the ECR plasma CVD method

Abstract: Properties such as the refractive index, etch rate and resistivity of silicon nitride films (SiN) prepared by an electron cyclotron resonance (ECR) plasma CVD method have been studied and correlated with their compositional and structural properties such as the N/Si ratio, bond configurations, spin density and film density. The microwave power, SiH4 flow rate under a constant flow rate of N2 gas and gas pressure during depositions, selected as the deposition parameters, were 50–500 W, 3–12 sccm and 4×10-4-4×10-3 Torr, respectively. The refractive index showed a unique correspondence to the N/Si ratio, but Si–H bonds had to be simultaneously taken into consideration in order to explain the dependency of the etch rate. The film density also had a strong influence on the film properties. The resistivity had a strong correlation with spin density, though it was also correlated with other properties such as the N/Si ratio. The compositional and structural properties of the films can be qualitatively explained by the optical emission spectra obtained from the ECR plasma of a SiH4–N2 mixture gas.

Effects of fines and velocity on fluid bed reactor performance

Abstract: In a pilot plant reactor it is shown that increasing fines content of the catalyst charge increases the conversion per unit residence time of gas. Similarly, increasing the velocity also increases the conversion. The results are explained using a model of combined diffusional and reaction resistance in the fluid bed.

Method for startup of production in an oil well

Abstract: A method of startup of oil production in a gas-lift well in which inlet flow (22) of gas is controlled (46, 42) while means (34, 28) controlling fluid flow from the well is progressively opened. Preferably, fluid flow rate from the well is monitored and valve means (28) opening rate reduced on detection of a greater than predetermined increase in flow rate. A method of controlling the oil production is also provided wherein flow rate from the well is monitored and a flow regulating device (28) in the flow path from the well controlled in accordance with that monitored flow rate which is indicative of the onset of slugging.