Showing papers on "Volumetric flow rate published in 1991"

Fluid control system

Abstract: The fluid control device of the present invention combines a flow sensing unit in series with a control valve. The flow sensing unit is of the displacement piston type and the flow rate is electronically sensed. A single action poppet valve assembly facilitates the use of a self contained power supply for use in remote locations. A microprocessor monitors parameters including pressure, flow rate, temperature and flow volume, and is enable to activate the control valve to the open or shut positions based upon any combination of the monitored parameters.

Measuring rate of heat release by oxygen consumption

Abstract: This paper provides a comprehensive set of equations and guidelines to determine the rate of heat release in full-scale fire tests based on the O2 consumption principle. The approach is different from other investigators as the enphasis is on full-scale fire test applications and the use of volumetric flow rates is avoided. Some general equations for flow rate (i.e., applicable irrespective of the configuration of the gas analysis system) are described first. In subsequent sections, distinctions are made between various gas analyzer combinations to derive the equations for rate of heat release. Procedures to calculate net rate of heat release from a specimen exposed to a gas burner or wood crib ignition source are also given. A summary at the end of the paper lists step by step procedures for all cases covered.

Convection transfer system

Abstract: A system provides convective transfer from a workpiece (10) to a flowing fluid. A gap (16) is formed between the workpiece (10) and a facesheet (12) containing fluid supply nozzles (18) and fluid return nozzles (20). The fluid is fed to the supply nozzles (18), travels a short distance within the gap (16) adjacent to the facesheet (12), and exits via return nozzles (20). The flow cross section and flow density facilitate heat transfer at a moderate flow rate and low fluid pressure. The system is also applicable for chemical transfer such as plating or etching printed circuit boards and for transfer through a semi-permeable membrane.

Borehole tool, procedures, and interpretation for making permeability measurements of subsurface formations

Abstract: A borehole tool has a source probe in fluid contact with the borehole wall, a fluid flow line for bringing fluids to and from the source probe, two injection fluid chambers containing clean oil and clean water and in fluid contact with the fluid flow line, at least one sample chamber for receiving fluid from the formation, valves for selectively routing the formation fluids and the clean oil and water through the fluid flow line, at least one pressure controller for controlling whether fluid is to be injected or withdrawn from the formation via the source probe, and a pressure gauge for measuring the pressure seen at the source probe. Permeability measurements are made by sequentially injecting one clean fluid into the formation, followed by a cleaning of the line with the other fluid which was not injected, followed by the injection of the other fluid into the formation. The order in which the oil and water are injected is based on the type of mud used for drilling. Using the sequential injection preceded and separated by cleaning, end point effective and relative permeability determinations are made by measuring the pressure seen at the probe during steady-state injection conditions of known flow rate in order to calculate mobility of the fluid phase being injected; the mobility being related to the end point effective permeability via the viscosity of the liquid being injected.

Instability of flow with temperature-dependent viscosity: A model of magma dynamics

Abstract: In material whose viscosity is very temperature dependent, flow from a chamber through a cooled slot can develop a fingering instability or time-dependent behavior, depending on the elastic properties of the chamber, the viscosity-temperature relationship, and the geometry of the slot. A laboratory experiment is described where syrup flows from a reservoir through a tube immersed in a chilled bath to an exit hole at constant pressure. Flow is either steady or periodic depending on the temperature of the bath and the flow rate into the reservoir. A theory indicates that the transition from steady to periodic flow depends on nonlinearities in the steady state relation between pressure and flow rate. A general stability criterion is advanced that states that the Peclet number must be within a certain range for instability to develop. Parameters governing the oscillation period are determined. Theory also indicates that flow through a slot would develop finger-like instabilities under certain conditions. Qualitative laboratory experiments with paraffin spreading over a cold plate reveal the fingering.

Viscoplastic flow in centered annuli, pipes, and slots

Abstract: A general method for the practical calculation of viscoplastic flows in centered annuli of arbitrary radius ratio is presented. The analysis is worked for the Casson, Herschel-Bulkley, and Robertson-Stiff rheological models, but the method is readily extended to other viscoplastic rheologies. A robust algorithm for the practical calculation of pressure drops and velocity profiles from given volumetric flow rates is presented, differing from other calculations where the pressure drop is the given parameter

Performance of TSI 3760 condensation nuclei counter at reduced pressures and flow rates

Abstract: This article describes an experimental study of the performance of the TSI model 3760 clean room condensation nuclei counter (CNC) at various pressures and flow rates. Studies were made to determine the counting efficiency of the instrument in the pressure range of 0.1–1 atm and flow rate range of 0.15–1.4 L/min. The counting efficiency curves were found to be shifted to larger particle sizes as the pressure or flow rate was reduced. The low pressure and low flow rate limits of the instrument were also determined. The numerical model developed in our previous study (Zhang and Liu, 1990) was used to predict the performance of the CNC. The numerical results were compared with the experimental data and found to agree well in the pressure range of 0.2–1.0 atm and flow rate range of 0.3–1.4 L/min. Discrepancies were found to be more significant at the lower pressures and flow rates. This is Particle Technology Laboratory Publication No. 759.

Adaptive filter flow control system and method

Abstract: An adaptive filter concentrate flow control system and method includes a filter system (12), a pumping system (14) driving feed fluid, concentrate and filtrate flowing through the filter system (12) and a flow control system (18) controlling the pumping system (14) to maintain optimum filtrage flow rates or minimum feed flow rates along a control surface (102) in a three dimensional transmembrane pressure (feed fluid rate) filtrate flow rate space: Actual sensed operating point data is used to locate the control surface (102) so as to assure an optimized filtrate flow rate or minimized feed flow rate at which reversible blocking of the membrane has begun to occur without irreversible blocking or plugging. The system is advantageously employed to control and maximize the flow of plasma in a plasmapheresis system or to minimize the rate at which blood is withdrawn from a donor and introduced into the system while achieving a fixed rate of plasma flow.

A study of inlet flow distortion effects on automotive catalytic converters

Abstract: This paper focuses on the influence exerted by a nonuniform flow distribution at the inlet of oxidizers to catalytic converters on conversion efficiency evaluated channel by channel. To this aim the flow inside the whole domain, constituted by the exhaust manifold and an elliptic- cross-sectional pipe connecting it with the converter shell, is simulated by means of a three-dimensional fluid-dynamic viscous model. In this way, after assigning typical converter size and geometry (i.e., elliptic) the gas flow rate distribution can be described at its inlet surface, also varying the total mass flow rate. After calculating the flow field at converter inlet by means of a three-dimensional model, evaluation is possible of local flow distortion in comparison with the ideal conditions of constant velocity of the gas entering the honeycomb converter channels.

Multiphase flow rate monitoring means and method

Abstract: The flow rate monitor includes a test line containing a chamber wherein the test line is declinated at a predetermined angle so stratification of liquid and gas will occur in the chamber. A sample stream is removed from the liquid in the chamber and provided to a separator which separates the gas from the sample stream to provide a gas output and a liquid output. The gas output and the liquid output is returned to the test line. The water cut of the liquid output is determined while the pressure of the composite petroleum stream is sensed along with the temperature. The volumetric flow rate of the composite petroleum stream is monitored and the flow rate signal is provided. The density of the composite petroleum stream is also monitored. The flow rate of all three coponents of the composite petroleum stream is determined in accordance with the temperature signal, the pressure signal, the water cut signal, the flow rate signal and the density signal.

An absolute charge sensor of fluid electrification measurements

Abstract: A new instrument, the Absolute Charge Sensor (ACS), has been developed that measures the net charge density entrained in a fluid flow, independent of the fluid's electrical properties, velocity, and any electrification processes within the instrument. Through a shielded sampling probe, the ACS periodically transfers a small volume of charged fluid to an electrically isolated Faraday cage with no fluid exiting. The charge density is calculated from the known filling flow rate and either the current or voltage, respectively measured by low or high impedance electrometers connected to the electrically isolated Faraday cage. The ACS overcomes the ambiguity in current or voltage measurements of probes placed into the fluid flow where it is impossible to separate contributions from impacting charge in the flow from charge separated at the probe interface by the very charge generation and transport processes that are under study. The instrument is typically operated to measure charge densities as low as a few mu C/m/sup 3/ using a sampling flow rate of 0.18 cm/sup 3/ with a sampling period on the order of 1 min. A Couette charger apparatus that simulates flow electrification processes in transformers and fuel pumps has been used to test the ACS using transformer oil or gasoline. Result show good correlation between the ACS and continuous flow measurements. >

Mathematical Modeling of Epitaxial Silicon Growth in Pancake Chemical Vapor Deposition Reactors

Abstract: Here, a mathematical model of the gas flow, transport phenomena, and growth rate profiles of epitaxial silicon in a pancake reactor is presented and the resulting modeling equations are solved. Two-dimensional conservation equations of momentum, energy, and mass developed in cylindrical coordinates along with appropriate boundary conditions are solved numerically with finite element methods. Streamlines of the gas flow in the reactor show that the shearing force of the inlet flow yields a recirculation zone inside the reactor and a separation point on the susceptor. As the inlet volumetric flow rate increases, the gas flow direction over the susceptor changes from inwards to outwards, resulting in another reverse circulating flow above the susceptor. The temperature and concentration profiles obtained show that steeper thermal and concentration boundary layers develop above the susceptor at higher volumetric flow rates. Under the assumption of a first-order deposition reaction on the substrate, growth rate profiles are calculated along the radial direction. The effects of total gas mixture flow rates, magnitude of the deposition rate constant, susceptor temperature, and thermal diffusion upon growth rate profiles are investigated. The agreement between observed and predicted growth rates at various temperatures is seen to be satisfactory

A Mathematical Model for Etching of Silicon Using CF 4 in a Radial Flow Plasma Reactor

Abstract: A mathematical model for plasma etching of silicon using tetrafluoromethane in a radial flow reactor was developed. Finite element methods were employed to calculate the two-dimensional flow, temperature, and species concentration fields. Etching rate and uniformity were studied as a function of reactor operating conditions, including the effect of flow direction. For the parameter values examined, the etching rate increased monotonically with flow rate. For low substrate temperature (298 K), inward flow resulted in higher etching rate as compared to outward flow, but the trend reversed at higher temperature. For flow rates greater than 200 sccm, outward flow with a uniform electron density distribution gave the best uniformity results. A one-dimensional radial dispersion approximation was used to study the effect of squarewave power modulation (pulsed-plasma reactor). The etching rate increased with decreasing pu]ise period and with increasing duty cycle. Under conditions which would result in high depletion of the precursor gas in a continuous-wave reactor (e.g., for low flow rates), the pulsed-plasma reactor can offer substantial improvement in uniformity without sacrificing the etching rate.

Characteristics of time varying void fraction in isothermal air-water concurrent flow in a horizontal capillary tube

Abstract: An experimental investigation was carried out on the varying properties of void fraction averaged over a tube cross section in an isothermal fully developed air-water two-phase mixture flowing in a horizontal capillary tube of 1.0mm, 2.4mm and 4.9mm inside diameter, using the constant current method. The flow pattern was observed by video and photograph with streak flashing. Calibration of the void meter was performed using a nonconductive plastic model in bubbly flow, intermittent flow and annular flow. It was found that the scatter of the data of the void fraction was within 20% in each flow region. We obtained correlations between (1) void fraction and gas volume flow rate quality, (2) bubble volocity and total volume flux, (3) lengths of slugs and gas-liquid flow ratio and (4) mean liquid film thickness and pipe diameter

Methods and systems for fluid identification and flow rate determination

Abstract: Methods and systems for determining the identity and flow rate of a fluid are provided. Linearized output signals are provided. To determine fluid flow, a test fluid is passed through a conduit. A heater associated with the conduit is maintained a temperature greater than the temperature of the conduit in the presence of the test fluid. A measuring voltage is generated, wherein the measuring voltage is indicative of the voltage required to maintain the heater at the specified temperature. A data set is provided to a computer, which compares the measuring voltage with a reference voltage and determines the identity of the test fluid. Further, a flow function is applied to the data set and the fluid flow rate is calculated.

Counting Efficiency of an Improved 30-Å Condensation Nucleus Counter

Abstract: The ultrafine aerosol condensation nucleus counter (UFACNC) developed by Stolzenburg and McMurry (1990) has been improved. This new instrument can detect particles as small as 30 A in nitrogen at a sample flow rate of 2.5 cm3·s−1. This flow rate is five times that of the earlier design with the same particle counting efficiency. An increased sample flow rate causes an increase in the arrival rate of detected particles. This improves accuracy in estimating the true particle concentration in ultraclean gas systems. In order to demonstrate its high accuracy the new UFACNC was used to measure the concentration of contaminant particles in ultrafiltered nitrogen. This represents the first accurate determination of ultrafine contamination levels in large ultraclean gas systems. The nitrogen was found to contain as few as 1.28 × 10−4 particles/cm3 (3.62/ft3). The higher volumetric flow rate of the new counter reduced the sample standard deviation of the measured count rate. Therefore, in the case of a low particu...

Flow sensor calibration

Abstract: A method and apparatus for calibrating a flow sensor composed of two heat sensors each having an electrical impedance parameter which varies as a defined function of the temperature of the heat sensor and disposed in thermal communication with a fluid such that the relation between heat flow to or from one sensor and heat flow to or from the other sensor varies with the rate of fluid flow, a source supplying electric power at a selected level to the heat sensors, and an output device connected to produce an output signal representative of that heat flow relation, calibration being performed by: establishing a known flow rate for the fluid; electrically connecting one of the heat sensors to a circuit element which alters the magnitude of current flowing through the one heat sensor; and determining, in a first determining step, output signal value while the one heat sensor is electrically connected to the circuit element.

Infusion rate regulator device

Abstract: A novel fluid flow regulating device for varying the rate of flow of fluids for infusion to a patient at extremely low but constant flow rates. The regulator device is interposed at a point on a supply tube between a fluid reservoir and a patient. An input port directs fluid to a fluid metering groove of variable cross-sectional area on a metering plate which is formed as a part of the output port. The metering plate is rotated axially, relative to the input port, allowing fluid to enter the fluid metering groove at any point and flow toward the output port through a fluid metering groove which increases in depth or cross-sectional area at an essentially constant rate. Depending on the point at which the fluid enters the fluid metering groove flow path, the flow rate selected can be any rate from full off to full flow.

Hydrodynamic relaxation in flow field-flow fractionation using both split and frit inlets.

Abstract: Two means are described for achieving hydrodynamic relaxation and thus avoiding the stopflow injection procedure in field-flow fractionation (FFF): split flow injection and frit inlet injection. The advantages, disadvantages, and the theoretical basis of these procedures are discussed. Incremental band broadening due to the final relaxation step is examined theoretically and shown to be negligible when the flow rate of the sample inlet substream is small compared to the total channel flow rate. The optimization of the sample inlet flow rate is discussed. Experimental results for both injection procedures are reported for flow/steric (or hyperlayer) FFF applied to latex standards, confirming the expected trends. However, closer examination shows that the observed incremental band broadening associated with hydrodynamic relaxation is somewhat larger than the value predicted.

Constant flowrate controller for an aerosol sampler using a filter

Abstract: A constant flow rate controller apparatus for an aerosol sampler using a filter includes an enclosed channel for channeling a stream of air, a filter positioned in the channel to capture and retain particles while allowing the stream of air to flow therethrough, an air or vacuum pump to pull the air through the filter, and a flow controller that maintains a constant volumetric flow rate of air through the sampler and filter, regardless of how much particulate matter is deposited on the filter or how much pressure drop across the filter changes due to particulate loading. The filter can be a substantially non-fibrous, porous, this film membrane medium, for which the flow controller of this invention is particularly beneficial, or it can be a more conventional fibrous medium. The flow controller can include a critical or choked flow orifice with a variable effective flow area, which effective flow area can be varied in response to changes in pressure drop across the filter to maintain constant volumetric flow rate. An expandable and contractible bellows with an appropriate spring constant can be used to both sense changes in air pressure drop across the filter or changes in stagnation pressure downstream of the filter and to actuate a variation in the effective flow area of the orifice in response to such changes in air pressure to maintain constant volumetric flow rate of the air. The air or vacuum pump has to have enough capacity to maintain critical or choked flow conditions in the orifice.

Calibration of a gypsum source for freshwater flow measurements

Abstract: A method for estimating flow rate in freshwater was refined by calibrating the rate of dissolution of inexpensive and easily made gypsum cylinders at flows of 0–10 cm∙s−1 and at temperatures between 3 and 25 °C. Gypsum flux was linearly related to flow (r2 > 0.94); thus, weight loss combined with the surface area of the gypsum source and exposure period allows an estimate of flux. Temperature-corrected estimates of flow, obtained from calibration equations and observed dissolution of gypsum cylinders, were virtually identical to flow measured with an electromagnetic current meter in five of eight comparisons conducted in a lake and in three rivers; the three other comparisons were within 0.95 cm∙s−1. The calibrations are suitable for inexpensive and quantitative estimates of flow in freshwater within the range of temperature and flow conditions typically encountered. We suggest that the method can be used for comparing flow regimes in virtually any marine or freshwater environment as long as salinity and ...

Method and apparatus for measuring mass flow and energy content using a differential pressure meter

Abstract: The present invention is a method and apparatus for monitoring in real time the mass and energy flow rate of a gas through a pipeline. The invention determines the ratio of the mass flow rate of pipeline gas flowing through a pipeline compared to the mass flow rate of sample gas tapped from the pipeline line. The invention involves tapping sample gas from the pipeline and flowing the sample gas to a capillary tube or a similar device for creating a pressure differential in a small flow. The sample gas is maintained at substantially the same temperature as the gas in the pipeline while the sample gas is in the capillary tube. The sample gas flows through the capillary tube continuously as controlled by a flow controller at a rate that is independent of the pipeline gas flow rate. A differential pressure cell measures the pressure differential of the sample gas across the capillary tube and also measures the pressure differential of the pipeline gas across an orifice in the pipeline. The mass flow ratio of the pipeline gas flowing through the pipeline to the sample gas flowing through the capillary tube is computed using the pressure differentials measured by the differential pressure cell. The energy content of the pipeline gas is determined by measuring the energy content of the sample gas and relating that value to the mass flow ratio of the pipeline gas compared to the sample gas. If the sample gas is a saturated hydrocarbon and is burned with air at maximum flame temperature, the energy content of the pipeline gas stream is mathematically related to the mass flow rate of the air and the mass flow ratio of the pipeline gas compared to the sample gas.

Sludge flow measuring system

Abstract: A system for the transport of high solids sludge includes a positive displacement pump for pumping sludge through a pipeline. The volume of sludge transported is accurately measured by determining the fill percentage by using a material flow signal, measured time intervals, hydraulic fluid pressure, or hydraulic fluid flow rate during each pumping cycle.

Closed loop fuel control system

Abstract: A fuel control system for accurately controlling the fuel flow rate to a gas turbine engine during the initial stages of startup is provided. The fuel control system has a novel, closed control loop that measures the actual fuel flow rate to the primary nozzles of the engine, and uses this measurement to trim the commanded fuel flow rate signal generated by preprogrammed schedules in the engine's electronic control unit. By the novel arrangement of proportional and integral controllers, the fuel control system maintains a forward path gain of unity while permitting the independent adjustment of the gain of the controllers to achieve the system stability and response necessary for quick correction of fuel flow rate errors.

The kinetics of flow‐induced crystallization from solution

Abstract: The flow-induced crystallization kinetics in a tubular flow geometry of 0.01 wt% solutions of a polyethylene fraction in xylene has been determined as a function of temperature and flow rate. Orientational properties of the crystallized fibers do not show a clear correlation with growth conditions (i.e., temperature and flow rate). The kinetic data are analyzed in terms of a modified form of the Avrami equation which provides a basis for separately correlating temperature and flow rate effects. The observed temperature dependency of the crystallization process can be interpreted in terms of nucleation and growth models while the flow rate dependency can be interpreted on the basis of entanglement formation arguments

Surface-acoustic-wave (SAW) flow sensor

Abstract: The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 degrees rotated Y-cut lithium niobate substrate and heated to 55 degrees C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cm/sup 3//min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves, propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized. >

Measurement of Residence Time Distribution of Fluid and Particles in Turbulent Flow

Abstract: Residence time distribution (RTD) of fluid and particles was measured in the holding tube of an aseptic processing system. A unique injector device instantaneously injected a large number of particles at one time without interruption of flow. A fraction collector device sampled exiting fluid at 1-sec intervals. Exiting particles at specific lapsed times from injection, were counted from those collected. RTD of fluid was determined by dye injection. RTD of fluid and particles under turbulent flow fitted a normal distribution function. Mean residence time of fluid was 0.975 times that calculated from volumetric flow rate with standard deviation ± 4.16%. Mean residence time of particles was 1.032 times that of the fluid, standard deviation was ± 4.62%.