Showing papers on "Pressure drop published in 1969"

The deformation of a drop in a general time-dependent fluid flow

Abstract: A theoretical method is given for the determination of the shape of a fluid drop in steady and unsteady flows by making an expansion in terms of the drop deformation. Effects of fluid viscosity and interfacial tension are taken into account. Examples given include the determination of the shape of a drop in shear and in hyperbolic flow when each is started impulsively from rest.

Pressure-Flow Relationships in Collapsible Tubes

Abstract: The pressure-flow characteristic of a short collapsible tube held open at its ends and inserted between two constrictions was investigated as a function of flow for different external pressures and downstream constrictions. Taking the upstream and downstream pressure and the flow through the tube as coordinates, a surface can be determined from which the results of any steady flow investigation at constant external pressure can be calculated. The surface has three regions corresponding to the open, partially collapsed, and almost completely collapsed tube. Steady flow through the tube was a multiple-valued function of the pressure drop across it. A collapsible tube is thus a flow-controlled nonlinear resistance, (QNLR) whose shape depends on external pressure and downstream circuit. The magnitude of the negative dynamic resistance (slope of the pressure drop-flow curve at the operating point) of the QNLR was approximately equal to the dynamic resistance of the downstream circuit. Negative dynamic resistance appeared when the tube collapsed at a critical transmural pressure independent of flow. The tube oscillated and amplified when the dynamic resistance was negative, but would not switch. An equivalent circuit for the tube was proposed with a variable compliance in shunt across a QNLR and variable inertance in series. Van der Polls equation qualitatively described oscillations in the tube. The collapsible tube model should apply to fluid conductors whose lumen significantly varies, for example, veins, coronary arteries, muscle pumps, and cardiac assist devices.

Pneumatic conveying of solids through straight pipes

Abstract: The pneumatic transport of solid particles in both horizontal and vertical pipes was studied using glass beads, copper spheres, millet and grass seeds, having diameters ranging from 0.1 to 1.0mm. It was shown that the additional pressure drop and the particle velocity could be expressed by ΔPs/L=0.057 (ua/√gD)mρa, and us=ua-ut, respectively, in the case of vertical transport. In vertical transport, the copper spheres and glass beads were found to be densely distributed toward the wall of the pipe whereas higher concentration near the axis was observed for, polystyrene particles. The velocity profile of the air in the vertical pipe was symmetrical and was not appreciably affected by the addition of the particles. However, in the horizontal pipe, the velocity profile was asymmetric with respect to the pipe axis, and was found to be affected by the particle diameter, density, and the mass flow ratio of the air and the particles. A simple impulsive model was used to explain the additional pressure drop in horizontal conduits, which was thought to be caused mainly by the collision between the particles and the surface of the pipe wall.

Slip flow through long circular tubes

Abstract: Slip flow of nitrogen gas through long circular tubes, measuring mass flow, pressure drop and cross sectional velocity profiles

Flow properties of suspensions with high solids concentration

Abstract: Equations were developed for evaluating the laminar flow behavior of high-solids suspensions from the physical properties of the liquid and solid components. A technique was developed for calculating suspension flow rates as a function of pressure drop. The technique is applicable to the design of pipe lines. Flow measurements were made in pipe-line viscometers of a unique design that minimized entrance and exit effects. Experimental flow data were obtained for suspensions consisting of nickel, alumina, copper, or glass solids in sodium, xylene, or glycerine vehicles with solids concentrations of 28 to 55 vol. %. The basis for the correlation of the data was an analytical investigation of the flow behavior that considered the particle-particle interaction that takes place in a settled suspension. The correlation equations fit all systems investigated. They take into account the effects of liquid viscosity, liquid and solid densities, particle size, size distribution, particle surface area, volume fraction of solids in the suspension, and volume fraction of solids at maximum settled conditions.

Flow in the hydrodynamic entrance region of ducts of arbitrary cross section

Abstract: A general method of analysis is presented for determining the developing velocity field and pressure drop for laminar flow in the entrance region of ducts having arbitrary cross sections. Application of the solution method is made to rectangular ducts and to triangular ducts. Available experimental data are compared with the analytical results and good agreement is found to prevail. Development characteristics for six ducts are brought together and compared, and various trends are identified.

Void Fraction and Current Density Distributions in a Water Electrolysis Cell

Abstract: An analytical basis defining the steady‐state conditions occurring in an electrolysis cell is stated. Several assumptions are made which permit a theoretical determination of the void fraction and current density distributions. The effect of void fraction and inlet velocity on cell performance is shown. Experimental data for the void fraction and slip ratio occurring in an electrolysis cell are presented. It is found that the slip ratio is near unity. This result is of importance in defining the cell void fraction distributions and is prerequisite to an analysis of pressure drop in electrolysis cells.

Particle Dynamics in Solids-Gas Flows in Vertical Pipe

Abstract: An investigation was carried out to study the particle dynamics of a known mixture of two narrowly sized particles for the first time. The flow characteristics determined by means of a special photographic technique (dot-streak-dot) were particle velocities, turbulence intensities, pressure drop, slip velocities and drag coefficients. The results are discussed with respect to the loading ratio, pipe Reynolds number, and composition of the mixtures. The particle velocity profile and the particle density distribution were analyzed in light of recent theoretical treatments on transport of solids in pipes. Moreover, the concept of volume/surface mean diameter as the representative diameter of the mixed-particle flow system is evaluated in correlating these flow parameters.

Electric field phenomena in fluidized and fixed beds

Abstract: Stabilization of a bed of dielectric particles against fluidization by an electric field (≥ 103 volts/cm) is described. Glass bead and silica gel particle beds have been observed to behave as packed beds with flow rates (and pressure drops) of the fluidizing gas up to 15 times the normal incipient fluidization rate. The pressure drop at the breakup of this fixed bed was dependent on the second power of voltage, the particular bed material, and geometry of the system. Under suitable conditions 100% bed expansion without diffusive particle motion or bubble formation was obtained using silica gel particles. Comparison with iron particle bed-magnetic field effects are presented. Surface polarization charge effects are the simplest explanation of the phenomena. Several of the possible applications are suggested, such as precipitation enhancement in an aerosol filter or as a new tool for investigating aggregative fluidization.

Venturi scrubber system including control of liquid flow responsive to gas flow rate

Abstract: In combination with a scrubber system which includes a venturi throat section for mixing a liquid with a laden gas stream, there are provided pressure measurement means in the flow path of the gas stream to provide a pressure drop measurement which shows an equivalent to pressure change across the venturi throat section. The system then effects, through differential pressure control means, an immediate change in liquid flow rate to such throat section responsive to the change in pressure drop such that a substantially constant pressure differential is maintained across the venturi and a resulting constant efficiency retained.

Steady-State and Unsteady-State Flow of Non~Newtonian Fluids Through Porous Media

Abstract: Non-Newtonian fluids may be injected into a reservoir during secondary recovery operations. The non-Newtonian fluid used in this work is a power-law type of fluid; that is, the viscosity of the fluid decreases as the flow rate or rate of shear increases. Equations are presented for steady-state linear and radial flow of such fluids, transient behavior results from a finite difference model of a radial system, and transient behavior results from a field test. The equations that describe the flow of a non-Newtonian fluid are non-linear and are solved numerically. Finite difference solutions are presented as curves of dimensionless pressure drop at the well bore vs. dimensionless time for a constant injection rate. Solutions were obtained for 5%, 10%, and 100% PV of a non-Newtonian fluid for injection rates of 1, 10, 100, and 1,000 cc/sec and for a 5% PV of non-Newtonian fluid located at r = rDwU, 3, 10, 20, 50, and 100 ft for a flow rate of 1 cc/sec. The buildup curves do not exhibit a straight-line portion as is the case for Newtonian flow through porous media. Correlations also are shown for the productivity index vs. rate for the computer model study and the fieldmore » tests.« less

Heat transfer and pressure drop for nitrogen flowing in tubes containing twisted tapes

Abstract: Heat transfer and pressure-drop studies were made on a series of electrically heated tubes containing full-diameter, full-length twisted tapes. The A nickel tubes had a nominal inside diameter of 0.4 in. (10.1 mm.) and a heated length of 12 in. (30.5 mm.). Nitrogen at 200 lb./sq.in. gauge (14.6 atm.) was the working fluid, and the tests covered the Reynolds number range from 20,000 to 200,000. Twist ratios, defined as the ratio of the tube length per 180 deg. twist to the tube diameter, were varied from 2.5 to 14. The effect of tube wall-to-gas temperature ratio was studied for values of up to 1.8 and the heat flux was varied from 104 to 105 B.t.u./hr. · sq.ft. (3 × 104 to 3 × 105 w./sq.m.). The results were compared with the results of previous heat transfer and pressure-drop studies and were generally found to be in good agreement. An empirical correlation was developed for the heat transfer results that accounts for the effects of twist ratio, wall-to-gas temperature ratio, and tube length and includes most of the previous single-phase results.

Internal bypass for a chemical reactor

Abstract: In a reactor containing a fixed bed of catalyst an internal bypass for reactants is provided to bypass the portion of the bed which is contaminated and offers the greatest pressure drop without changing the direction of flow of the reactants The internal bypass is of particular advantage in a hydrodesulfurization process utilizing very small catalyst particles wherein pressure drop is critical and wherein an external bypass which changes flow direction might impart a greater pressure drop than it conserves by avoiding a contaminated section of catalyst

Waterflood relative permeabilities in composite cores

Abstract: When cores longer than about 3 in. are desired for waterflood testing, it is common to assemble a composite core from a set of short core pieces. The assumptions made in using such a composite core for waterflooding testing are that all the core selections: (1) have nearly identical relative permeability curves, (2) are homogeneous and isotropic, and (3) have nearly identical connate water and residual oil values. It is further assumed that there is good contact between sections and that the flooding rate is high enough to make capillary pressure effects unimportant in all core sections. To test the validity of the proposed ordering scheme, waterflood simulations were performed using one-dimensional, 2-phase difference equation approximations to describe immiscible water-oil displacement. The difference equations, which were implicit in water pressure and capillary pressure, were solved using a Newtonian residual iteration scheme with the alternating direction iteration procedure (ADIP). After the waterflood simulation was performed from the resulting fluid production and pressure drop data, a set of waterflood relative permeability curves was calculated using the standard computational procedure applicable to homogeneous cores.

Method and apparatus for sensing downhole well conditions in a wellbore

Abstract: A method and apparatus for sensing downhole well conditions in a wellbore having a drill string suspended therein and pump means and conduit means for circulating drilling fluid down the well. The apparatus includes a pressure transmitter for sensing the circulating pressure of input drilling fluid being circulated down the well and generating a first signal representative thereof. It could also include means in the form of a differential pressure transmitter for sensing a pressure drop of the drilling fluid along a portion of the conduit means and generating a second signal representative thereof. Readout means in the form of dual concentric pressure gauges are provided for reading out a change between the signals as an indication of a change in downhole well conditions, such as loss of drilling fluids or incursion of formation fluids into the well.

A note on the damping and oscillations of a fluid drop moving in another fluid

Abstract: The oscillations of a drop moving in another fluid medium have been studied at low values of Reynolds number and Weber number by taking into consideration the shape of the drop and the viscosities of the two phases in addition to the interfacial tension. The deformation of the drop modifies the Lamb's expression for frequency by including a correction term while the viscous effects split the frequency into a pair of frequencies—one lower and the other higher than Lamb's. The lower frequency mode has ample experimental support while the higher frequency mode has also been observed. The two modes almost merge with Lamb's frequency for the asymptotic cases of a drop in free space or a bubble in a dense viscous fluid but the splitting becomes large when the two fluids have similar properties. Instead of oscillations, aperiodic damping modes are found to occur in drops with sizes smaller than a critical size ($\sim\hat{\rho}\hat{ u}^2/T $). With the help of these calculations, many of the available experimental results are analyzed and discussed.

Boiling Heat Transfer and Pressure Drop of Liquid Helium-I under Forced Circulation in a Helically Coiled Tube

Abstract: Boiling heat transfer to liquid helium-I has a number of practical applications, such as the cooling of superconducting magnets, space simulators, cryotrons, cryopumping devices, and masers. Although the bath immersion technique is used extensively for the cooling of such devices, a forced circulation technique might in some cases be more effective.

Hydraulic system circuit breaker

Abstract: A hydraulic circuit breaker or fail-safe device is disclosed for sensing leaks in lines to and from hydraulic actuators or the like. Flow through the line is sensed across a restriction on a piston valve member movable to close the line, the size of the restriction being such that flow in excess of normal requirements causes a significantly increased pressure drop, which drop is sensed across a quantity measuring piston movable in a chamber within the piston-valve, and causing the latter piston to move within its chamber at a rate controlled by the area of a control orifice. As this latter piston moves, it carries a shaft which is spring biased to resist movement until the pressure drop across the restriction reaches a value indicative of a leak. Two spool valve members are carried on the shaft whose function in the two embodiments shown is to direct either supply pressure or lower pressure against operating areas of the piston-valve to control its movement to open or close the line. A check valve is placed in a return line and an additional piston in contact with the biasing spring senses a leak in the return line as indicated by a changed pressure drop across the check valve and moves to either remove the effective spring bias on the shaft or to move the shaft directly such that the spool valve members direct flow to cause the piston-valve to close the line.