Showing papers on "Volumetric flow rate published in 1990"

Continuous measurement of cardiac output with the use of stochastic system identification techniques.

Abstract: The limitations of developing a technique to measure cardiac output continuously are given. Logical explanations are provided for the economic, technical, and physiologic benefits of a stochastic system identification technique for measuring cardiac output. Heat is supplied by a catheter-mounted filament driven according to a pseudorandom binary sequence. Volumetric fluid flow is derived by a cross-correlation algorithm written in the C language. In vitro validation is performed with water in a flow bench. The computed flow (y) compared with the in-line-measured flow (x) yields the linear regression y = 1.024x - 0.157 (r = 0.99). The average coefficient of variation is less than 2% over a volumetric fluid flow range of 2 to 10 L/min.

Selecting a working fluid to increase the efficiency and flow rate of an EHD pump

Abstract: The ultimate flow rate and velocity of an electrohydrodynamic (EHD) pump with a given length and depth are determined by the material properties of the working fluid. High dielectric constant, and low viscosity lead to high flow velocities, while low conductivity and mobility promote high efficiency. A fundamental model of EHD pumping is formulated to account for the material properties of the working fluid, and is applied to several experimental pumps reported earlier, with generally good agreement. An example of the use of this model to select a working fluid for a typical pump suggests several new liquids suitable for EHD pumping. >

Volumetric blood flow via time-domain correlation: experimental verification

Abstract: A novel ultrasonic volumetric flow measurement method using time-domain correlation of consecutive pairs of echoes has been developed. An ultrasonic data acquisition system determined the time shift between a pair of range gated echoes by searching for the time shift with the maximum correlation between the RF sampled waveforms. Experiments with a 5-MHz transducer indicate that the standard deviation of the estimate of steady fluid velocity through 6-mm-diameter tubes is less than 10% of the mean. Experimentally, Sephadex (G-50; 20-80 mu m dia.) particles in water and fresh porcine blood have been used as ultrasound scattering fluids. Two-dimensional (2-D) flow velocity can be estimated by slowly sweeping the ultrasonic beam across the blood vessel phantom. Volumetric flow through the vessel is estimated by integrating the 2-D flow velocity field and then is compared to hydrodynamic flow measurements to assess the overall experimental accuracy of the time-domain method. Flow rates from 50-500 ml/min have been estimated with an accuracy better than 10% under the idealized characteristics used in this study, which include straight circular thin-walled tubes, laminar axially-symmetric steady flow, and no intervening tissues. >

Transport mechanisms in iontophoresis. I. A theoretical model for the effect of electroosmotic flow on flux enhancement in transdermal iontophoresis.

Abstract: Bulk fluid flow or volume flow in the direction of counterion flow is a probable mechanism for enhanced flux of uncharged species by iontophoresis. Both the electrical volume force effect, resulting from the interaction of the “ion atmosphere” and the electric field, and an induced osmotic pressure effect produce volume flow in the same direction as counterion flow through the membrane. Since each of these effects is proportional to the membrane charge and the imposed electric field, we classify both as electroosmotic flow. This research develops a detailed theoretical model which allows the effect of volume flow on flux enhancement to be evaluated. A detailed theoretical result for the electroosmotic flow coefficient also results from the analysis. The model assumes that transport occurs in three types of aqueous pores: positively charged, neutral, and negatively charged. For hairless mouse skin (HMS), pore size, charge, and number are evaluated from transference number, volume flow, and electrical resistance data. The flux enhancement ratio is J1/J1D= ΣAiαi/[l –exp( –αi)], where i = pore type, and the summation runs over the three pore types. Ai is the area fraction of pore type i effective for transport; J1 and J1D are flux of species 1 with and without the electric field, respectively; and αi is given by αi = F(–ΔΦ/RT)[ z1 + (−zmi)Bari2Cmi(Gi + F)]. Here F = Faraday's constant; −ΔΦ = voltage drop; R = gas constant; T = absolute temperature; zmi = charge of pore i; Cmi = charge concentration in membrane pore of radius, ri; B is a known collection of constants; a is the Stokes radius of the transported solute; Gi, is a function of membrane charge and pore radius coming from the electrical volume force effect; and F is a function of membrane charge and ion mobility arising from the induced osmotic pressure effect. For transdermal iontophoresis, F 0) or a neutral species (z1 = 0) in a negatively charged pore. The theoretical results are consistent with data in the literature.

Flow patterns and pressure drop in isothermal gas-liquid concurrent flow in a horizontal capillary tube.

Abstract: A gas-liquid two-phase flow in a capillary tube or a narrow passage is encountered in many applications, for example, the flow of coolant in evaporators of many kinds of heat exchangers. Sufficlent information on fundamental parameters, such as void fraction and pressure drop, however, are not available in designing such devices. In the present investigation, we made a detailed observation of the flow pattern of an air-water two-phase flow in a horizontal capillary tube with an inner diameter of 1.0mm to 4.9mm, and attempted to correlate and explain the behavior of the pressure drop changing with the flow rates of both phases by introducing a physical model.

Mass flow controller with supplemental condition sensors

Abstract: An improved mass flow controller can be connected to a passageway of a fluid, and can utilize a sensor unit for measuring a characteristic of the mass flow, and deriving a corresponding flow rate signal. Supplemental condition sensors can measure other parameters of the flow rate independent of their utilization in determining the actual flow rate, and can monitor and compare the current value of these sensor conditions, with standards to thereby monitor the operational performance of the mass flow controller.

Dependence of polymer apparent viscosity on the permeable media and flow conditions

Abstract: It has been observed that the apparent viscosity of polymer solutions in porous media is often lower than the polymer viscosity observed in viscometers at the same shear rate. The effective shear rate in the core is typically calculated using a capillary bundle model for the flow of non-Newtonian fluids in porous media. To correct for the discrepancy, these models are usually modified by an empirical coefficient, called the shear rate coefficient, which attempts to relate the flow in a capillary bundle to that in porous media. The authors have analyzed data from the literature and data taken for a variety of polymers, porous media, and flow conditions. Some of their new data include flow in heterogeneous media. The shear rate coefficient appears to vary over a wider range than previously appreciated based upon much more limited experimental data than analyzed in this paper. A correlation is proposed for the purposes of giving a rough estimate of the shear rate coefficient when only the permeability, porosity, flow rate, and polymer type are known.

Methods for detection of leaks in pressurized pipeline systems

Abstract: A method of determining the presence and temperature compensated volumetric flow rate of leaks in fluid pressurized pipelines The pipeline is maintained at a first pressure and the fluid volume change per unit time is calculated The pressure is then maintained at a second different pressure and a second fluid volume change per unit time is calculated The system is then maintained at the first pressure while a third fluid volume change per unit time is calculated The first and third rates are combined with the second rate to obtain a temperature compensated leak volumetric flow rate

Bi-flow expansion device

Abstract: A bi-flow expansion device for a heat pump or other apparatus where fluid avel is reversed with different required flow rates in each direction. The device comprises a tubular member mounted in a refrigerant line and having non-symmetrical entrance-exits at the ends of the tubular member for changing the mass flow rate of refrigerant through the expansion device when the direction of refrigerant flow is changed.

System for evaluating the flow performance characteristics of a device

Abstract: A system for determining the flow performance of a valve by first measuring certain flow parameters of the valve with the stem fixed in a plurality of different positions between full open and full closed and then calculating a value of flow coefficient for each. The flow parameters of the valve are then measured with the stem dynamically moving under a plurality of different flow conditions. Mathematical relationships are derived in accordance with certain procedures for calculating the flow rate of the valve under each of the different flow conditions.

Method and apparatus for collecting samples for analysis of chemical composition

Abstract: An automated, on-line solvent elimination interface system is described for use in characterizing the Composition Distribution (CD) of unknown materials emerging from a fractionating unit or a process stream. Fractionated samples to be analyzed, such as a polymer, in highly diluted form in one or more solvents, are provided by a fractionation unit such as a gel permeation chromatograph (GPC), a high pressure liquid chromatograph (HPLC), or a field flow fractionator (FFF). A number of discharges of each particular fraction are supplied to individual collection units within the interface system under controlled conditions of flow rate, temperature and pressure (vacuum) such that the solvents are flash-evaporated at the collection unit. A sufficient solid residue is built up on the collection unit for analysis by, for example, a Fourier transform infrared (FTIR) analyzer.

Method and apparatus for real time compensation of fluid compressibility in high pressure reciprocating pumps

Abstract: The invention is a method and apparatus for significantly improving the performance of a reciprocating pump by delivering the pumping fluid at a desired pressure and flow rate with minimal flow fluctuations. The compressibility of the pumping fluid directly effects volumetric flow rate and mass flow rate. The method includes the step of sensing various pump parameters related to said compressibility and adjusting the pumping speed to make appropriate accommodations. In particular, the compressibility of the pumping fluid is effected by the adiabatic heating of the pumping fluid during compression, variations in pumping fluid density, leaks in the check valves of cylinder/piston seals and the primary and secondary switching losses in the fluid flow occurring when the primary and secondary pistons reverse direction.

Dependence of the Performance of TSI 3020 Condensation Nucleus Counter on Pressure, Flow Rate, and Temperature

Abstract: A theoretical study has been carried out to investigate the performance of the TSI 3020 condensation nucleus counter (CNC) at various pressures and flow rates by assuming a parabolic velocity profile in the condenser tube and solving the heat and mass transfer equations using the finite difference method. Calculations have been performed for pressures ranging from 0.03 to 10 atm and sampling flow rates from 0.5 to 50 mL/s. The results indicate that the counting efficiency of the CNC is a function of pressure and flow rate due to changes in heat and mass transfer rates. The counting efficiency can be correlated with a single parameter, ζ, which combines the effects due to pressure, sampling flow rate, and the length and diameter of the condenser tube. The cut size of the instrument, Dp50, defined as the particle size at which the counting efficiency is 50%, has been found to vary with pressures, reaching a minimum at a pressure of approximately 1 atm. The cut size of the CNC has been found to be most sensi...

Fluidic volumetric fluid flow meter

Abstract: Fluidic volumetric flow meter method and apparatus wherein undesirable dynamic interaction (ringing) which could appear in an output signal is inhibited. Electrical isolation and shielding also contribute to a high quality output signal in accordance with the invention. Particularly advantageous housing structures adapt the flow measurement device to a variety of applications as a complete flow meter.

Flow of Non-Newtonian Fluids Through Eccentric Annuli

Abstract: The laminar eccentric annular flow of non-Newtonian fluids is analyzed with a new method where an eccentric ammulus is represented by an infinite number of concentric annuli with variable outer radii. The analytical solutions for the shear stress, shear rate, velocity, and volumetric flow rate/pressure gradient are obtained for both power-law and Binham-plastic fluids. This method is shown to provide more accurate approximations for various profiles and good predictions of the volumetric flow rate/pressure gradient in eccentric annular flow. In addition, turbulent eccentric annular flow is discussed.

Streaming electrification study of transformer insulation system using a paper tube model

Abstract: A simple flow model was designed to simulate oil flow in the insulation ducts of power transformers. It consisted of an annular paper tube, relaxation tanks, pump, and flow controls. Laminar and turbulent flow modes were studied in the temperature range from 27 to 70 degrees C. Current development was monitored as a function of temperature and flow velocity. The temperature dependence was approximately of the Arrhenius type; no current peak was observed as reported for transformers in the temperature range studied. The current increased linearly with flow velocity at low flow rates and increased as the square of velocity at high flow rates with a gradual transition in the intermediate range of flow. The voltage development was characterized by a sharp rise initially as the flow was turned on, leveling off to a maximum after several minutes. Partial discharge patterns were observed in the volt-time plot, increasing in frequency and temperature at elevated temperatures and flow velocities. A strict application of the test results to transformers is not possible due to unknown parameters. >

Design of coaxial segmentors for liquid-liquid extraction/flow injection analysis

Abstract: The process of the segmentation of two immiscible solvents by newly introduced coaxial segmentors of different geometry was studied in a continuous liquid-liquid extraction flow system. A fast reading «on-tube» photometric detection system (∼3 ms time resolution) controlled by a computer was used to measure optical transparency directly across the flowing stream. The influence of flow rates, flow rate ratio, the density and interfacial tension of the phases as well as the geometry of the segmentors was studied

Coatings and surface modification by methane plasma polymerization

Abstract: Polymers formed from plasma-polymerized methane were employed to modify the surface properties of silicone rubber membrane. Polymers were evaluated based on the energy input parameter W/FM, where W is the discharge power, F is the monomer flow rate, and M is the molecular weight of the monomer. Dealing with the characteristics of plasma polymerization and the deposited polymer film, the effect of pumping rate on deposition rate and the coating thickness, surface energy, and gas permeabilities of methane-plasma-polymer-coated silicone rubber membrane were investigated in three plasma regions. Because more reactive species are expelled at high pumping rates, the monomer-deficient region is reached at lower W/FM in the high pumping rate system than that in the low pumping rate system. The composite parameter W/FM had a strong influence on coating thickness, gas permeability, surface energy, and the polar component of the surface energy but little effect on its dispersion component. Examination of gas permeabilities indicated that coating thickness was another important controlling factor on the properties of plasma polymer.

Ideal flow models for palladium membrane reactors.

Abstract: The effects of flow patterns on the dehydrogenation performance of palladium membrane reactors in which a sweep gas is used to remove the permeated hydrogen were examined. By combining two idealized flow patterns, plug and perfect mixing flows, to the reaction and separation streams, five flow models—cocurrent, countercurrent, plug-mixing, mixing-plug, and mixing-mixing models—were analyzed and compared.It was evident that the countercurrent model leads to the highest degree of conversion and the shortest reactor length requirement while the performance of the mixing-mixing model is the lowest, except when the flow rate of sweep gas chosen is comparatively small. The order of performance among the other three models was dependent on the variables used in calculations.

Method for determining dynamic flow characteristics of multiphase flows

Abstract: A method for determining at least one dynamic flow characteristic of a multiphase flow circulating in a pipe, the flow being composed of a lighter dispersed-phase and a heavier continuous-phase. A tracer is discharged (or activated) into the flow at a chosen first location in the pipe by mixing (or activating) a portion of the tracer with the continuous-phase therein. The tracer concentration at a chosen second location in the pipe is measured with a detector as a function of time t, so as to obtain a signal S(t). Then a relationship is fitted to the signal S(t) so as to derive the values of the velocity U of the continuous phase and/or of a dispersion coefficient k. The slip velocity v s of the dispersed phase relative to the velocity of the continuous phase is also advantageously determined. From the values of velocities U and v s and from the volume fraction y 1 of the continuous phase in the pipe (obtained by an ancillary measurement), the volumetric flow rates of the continuous and dispersed phases are determined.

Flow of polymer solutions through porous media

Abstract: The flow of polymer solutions through porous medias has been investigated at different temperatures (278, 283, 288, 293, 298, and 303 K) and flow rates (from 0.659×10 -6 to 22.29×10 -6 m 3 /s). The ranges of shear rates and pressure drops were 10.8-692.5 s -1 and 0.414×10 5 to 2.72×10 5 Pa, respectively. Three different kinds of polymers (polyacrylamide, 1000 ppm concentration) were used in a 100-mm column packed with 2-mm particle diameter glass beads. Two types of modifications for Darcy's law were tested and discussed in the form of modified friction factor-Reynolds number correlations. First, the modified Blake-Kozeny equation for the flow of power law fluids through porous media was tested experimentally; second, a viscosity-temperature-shear rate correlation was developed and applied in the Blake-Kozeny equation for the flow of Newtonian fluids through porous media

Steam quality and flow rate measurement

Abstract: A method and apparatus for measuring both the quality and flow rate of steam injected into a hydrocarbon formation in a thermal recovery process. The method measures both the quantity of water and the flow rate of the steam. Both measurements can be made at any location in the borehole to determine the quality and quantity of steam injected into a particular formation. The apparatus utilizes a propeller motor/generator combination to determine the vapor flow rate; the drag produced by a network of bristles extending across the borehole determines the vapor flow rate and the quantity of liquid present.