Showing papers on "Pressure drop published in 1975"

Pressure drop across artificially induced stenoses in the femoral arteries of dogs.

Abstract: Stenoses were artificially induced in 13 large mongrel dogs by implanting small hollow cylindrical plugs in their femoral arteries. The instantaneous pressure drop across the stenosis and the flow rate were measured for a series of stenoses varying in severity from 52.3 to 92.2%. Mean pressure drops ranged from approximately 2 to 30 mm Hg with peak pressure drops ranging from 9 to 53 mm Hg. The pressure drop could be estimated from a relatively simple equation that was originally developed for flow through model stenoses. With this equation, the effects of several factors that contribute to the pressure drop, including stenosis size and shape, artery lumen diameter, blood density, blood viscosity, and velocity and acceleration of flow, could be clearly delineated. For severe stenoses, unsteady flow effects were small and flow could be treated as quasi-steady. Calculations based on data obtained from the dog experiments revealed that the mean pressure drop across a stenosis increased nonlinearly with percent stenosis and showed quantitatively that the value of critical stenosis decreased with increasing demand for blood flow.

Abnormal Formation Pressure

Abstract: Abnormal formation pressure requires a seal; without a seal pressures would equalize to normal hydrostatic. Abnormal pressures originate from several interrelated processes, but temperature change appears to be the principal cause. Both epeirogenic movements with associated erosion and deposition and long-term changes in climate can alter the temperature of a sealed formation at depth. Abnormal pressure resulting from temperature change caused by change of overburden thickness must be corrected for inherited pressure and change of hydrostatic pressure related to elevation difference. Osmosis, precipitation, or solution by trapped pore fluid and carbonization effects are minor in comparison with temperature effects. Overburden stress cannot cause abnormally high pressure at present drilling depths. The loss of porosity with depth in all sedimentary rocks appears to be a chemical process rather than mechanical compression. Pressure differentials between wells may indicate ambiguously either no fluid flow (wherein the pressure difference is maintained by a seal) or flow (wherein the pressure drop is from fluid friction in the permeable medium). A relatively small amount of flow across a seal can equalize pressures, retarding further flow. The fluid expelled as a result of loss of porosity during geologic time also flows at a low rate. The geologist concerned with pressure problems must be aware of (1) the many variables involved in subsurface pressures, (2) the low number and ambiguity of pressure measurements, (3) the need to establish what constitutes "normal" pressure to determine abnormal pressure, and (4) the possibility of uniqueness in any field situation.

The laminar flow of dilute polymer solutions through porous media

Abstract: Measurements of the pressure drop and flow rate were obtained for dilute solutions of polyethylene oxide flowing through beds of packed beads When the velocity was sufficiently high, the pressure drop was above that for a Newtonian fluid of equal viscosity, often considerably above, and this viscoelastic effect was explored by varying the concentration and molecular weight of the polymer, by testing solutions over a wide range of flow rates, and by using several bead sizes The non-Newtonian behaviour was most pronounced at moderate flow rates; at the highest velocities, the data were pseudo-Newtonian in character, ie the pressure drop still exceeded that for a Newtonian fluid, but was linearly related to the velocity For some solutions, the large deviation from Newtonian values occurred over such a short range of flow rates that there was an interval in which the pressure drop decreased with velocity It was not possible, therefore, to obtain steady-state measurements in this regime and a gap appears in the data curve of pressure vs velocityThe pressure drop was monitored in steps along the test section, so that it was possible to detect molecular degradation of the solutions as they flowed through the porous media In general, degradation was not extensive and the solutions became stably degraded by the midpoint of the test section Degradation increased with velocity and, quite surprisingly, became more severe as the bead size increasedA visual examination of the flow field revealed that the streamline pattern for the polymer solutions was the same as that for water The large non-Newtonian effects were therefore due to changes in the stress field, and in an effort to understand these effects, an analysis was carried out which examined how the stresses generated by each component of the deformation, ie by shear and pure strain, influence the pressure drop This analysis, combined with a study of onset data, indicates that onset and the sudden large departures from Newtonian values are probably due to an interaction between extensional and shearing deformation, and that the reduced viscoelastic effect of higher flow rates may be due to the dominance of extensional stresses

Statistical characteristics of thin, wavy films III. Structure of the large waves and their resistance to gas flow

Abstract: Two classes of random waves exist on falling films at flow rates of practical interest; large waves which carry the bulk of the liquid and small waves which cover the substrate. In this paper statistics of the large waves are presented and compared with existing theory. These waves are bimodal in character at ReL > 700. The form drag of the large waves is shown to contribute negligibly the observed pressure drop in the gas phase. It is thus concluded that the small wave structure controls the fluid resistance and transfer processes in the gas while the large waves control these same processes in the liquid film.

The creeping motion of liquid drops through a circular tube of comparable diameter

Abstract: The creeping motion through a circular tube of neutrally buoyant Newtonian drops which have an undeformed radius comparable to that of the tube was studied experimentally. Both a Newtonian and a viscoelastic suspending fluid were used in order to determine the influence of viscoelasticity. The extra pressure drop owing to the presence of the suspended drops, the shape and velocity of the drops, and the streamlines of the flow are reported for various viscosity ratios, total flow rates and drop sizes.

Drag reduction in solid‐fluid systems

Abstract: Pressure drop measurements were made on a variety of dilute solid-liquid suspension systems in order to study the effects of particle shape and size, concentration, fluid viscosity, and tube diameter on friction factor. The central objective was to determine under what conditions drag reduction would occur.

Laminar flow of non-newtonian fluids in an eccentric annulus

Abstract: Esso Production Research Co. developed a technique for predicting the volumetric flow rate and velocity distribution for laminar flow of power-law and Bingham-plastic fluids in an eccentric annulus. This flow situation occurs during drilling of cementing of oil or gas wells. The volumetric flow rate is presented as a series of dimensionless plots of fluid properties, pipe diameters, eccentricity, and pressure drop, which are obtained by numerically integrating the velocity profile from a finite difference solution of the equations of continuity and motion after transformation into bipolar coordinates. The numerical procedure was verified by comparing the calculations with previously published results for the special cases of Newtonian flow in an eccentric annulus and non-Newtonian flow in a concentric annulus and with limited experimental data for Bingham-plastic flow in an eccentric annulus. The results indicate that the technique is accurate in predicting the volumetric flow rate and velocity distribution within the range of variables specified and on the degree of conformity of the fluid to the rheological model used.

Electronic fluid pipeline leak detector and method

Abstract: Disclosed is an instrument wherein the pressure or flow of a fluid in a pipeline is monitored with a voltage proportional thereto being electronically differentiated to determine whether any rate of change of pressure exists, which is often indicative of a leak in the pipeline. If a rate of pressure change of a predetermined extent exists for a predetermined period of time and if a total pressure change exceeds a predetermined value, an output signal can close a valve in the pipeline or can sound an alarm. In addition, in situations where a liquid is involved, a surge develops upon a line break, that is, a large rate of instantaneous pressure drop, and such surge can also be detected and appropriate remedial measures taken. The instrument is also capable of shutting down the pipeline in instances of inordinately low or high pressure conditions.

Automotive oil cooler

Abstract: Submerged oil cooler for automotive vehicles requires only two principal parts but can provide more heat transfer at a lower pressure drop than conventional oil coolers which utilize three principal parts. In a preferred embodiment, an outer tube having a plurality of longitudinal flutes which are periodically transversely indented is press fit over an inner tube having a helically finned outer surface. The tubes are sealed at their ends so as to define an extended annular flow channel for oil between the tubes, while permitting engine coolant in which the cooler is submerged to flow through the inner tube. A modified arrangement substitutes corrugated tube for the finned inner tube with a resulting cost saving in material but with a small increase in pressure drop and a small loss in heat transfer efficiency.

Material distributing and mixing apparatus

Abstract: Apparatus for mixing or distributing a material or materials having no moving parts in which one or more elements are fitted into a conduit. Substantial radial displacement of material flowing in the conduit is achieved over a short distance with minimum pressure drop. Each element initially imparts a rotational vector to the material stream and then transforms the rotational vector to a lateral or radial vector.

Heat and pressure effect in viscous flow through a pipe

Abstract: The basic relations governing viscous flow of liquids with variable transport properties is considered. A dimensional analysis of the problem is given, and the basic equations of generalizedNewtonian flow through a pipe are derived. A perturbation solution is given for the special case of aNewtonian liquid with pressure and temperature dependent viscosity and expressions for the velocity components, pressure distribution and flow rate are obtained for both isothermal and adiabatic wall conditions. It is shown that pressure and viscous heating effects may result in apparently nonNewtonian behaviour.

Thermal transfer care

Abstract: A heat exchanger for transmitting thermal energy from one moving fluid to another of the type having a casing housing a thermal transfer core, the core including a folded sheet of heat conductive material defining adjacent fluid flow passages, the individual fold sections of the sheet having a multiplicity of pairs of dimples formed therein, each dimple pair including a raised dimple and an adjacent depressed dimple, the height of each dimple being substantially equal to one-half the width of the fluid flow passages. The dimple arrangement provides a relatively low pressure drop for the fluids passing through the fluid flow passages.

An evaluation of a ceramic monolith as an enzyme support material

Abstract: Catalase was immobilized on commercially available monolithic catalyst supports and also on participate support obtained by crushing the monolith. The kinetics of the monolith- and particulate-supported enzymes were analyzed in a continuous tubular reactor system and pressure drop was also monitored. Analysis of the results indicates that the monolith-supported system presents very little resistance to flow which results in a considerably smaller pressure drop than is obtained in flow through particulate-supported systems under comparable conversion conditions. Ceramic monoliths thus appear to be very suitable for use as enzyme supports in continuous tubular reactor applications, particularly where high pressure drops might be expected.

Pressure responsive self-purging emitter

Abstract: An emitter for use in drip irrigation systems which is both self-purging and pressure responsive to provide substantially constant flow rates with varying inlet pressures. The emitter includes a flow path which consists of a series of interconnected openings in each of which is positioned a valve including a valve lip which extends across the opening in which it is located and is directed in an upstream direction so that as the pressure drop across any one valve increases, the effective area of the flow path at that valve will decrease to maintain a substantially constant flow rate. When the pressure drop at a particular valve increases above a predetermined amount, as when a particle of dirt or other foreign substance clogs the valve, the valve lip travels over center and allows the clogging particle to pass, thereby purging that particular valve and permitting it to return to its normal operating position. The emitter is preferably formed with a resilient central body portion and relatively rigid outer cover plates. In one embodiment the flow path openings and interconnecting passages are formed in the central body portion. In a second embodiment the openings and interconnecting passages are formed in the cover plates and the central body portion comprises a sheet of resilient material having tongues struck therefrom which project into the flow path defined by the contoured cover plates when the emitter components are assembled.

Valve with improved flow passage

Abstract: A flow passage providing improved pressure recovery in a valve having an axially movable closure element which includes the provision of an annular diffuser flow passage from the seat port to the periphery of the closure member to reduce the fluid pressure drop across the valve when the closure member is moved a limited distance to its fully open position. The annular diffuser flow passage is provided between a pair of oppositely disposed frusto-conical surfaces respectively provided on the valve body and the closure element. The closure member may also be provided with a convexly shaped projection and the valve flow passage shaped to further reduce the pressure drop across the valve.

Mixing and dispensing apparatus

Abstract: A static mixing chamber for mixing multi-component compositions has the provision of having the mixing chamber at the outlet of the feed lines. A valve is at the outlet end of the chamber. By having the chamber near the outlet end, a large pressure drop across the chamber is insured. Moreover, the valve at the end of the chamber insures that the large pressure drop will be maintained even during start-up of dispensing. By increasing the pressure drop over the chamber, mixing therethrough has been greatly enhanced. Therefore, a smaller mixture is required for effective mixing. The result in small size makes the static mixer capable of being hand held, in the form of a dispensing gun and the valve actuator is part of the dispensing gun so that the valve can be operated by the same hand that is holding the gun.

Cooling system for a thrust vectoring gas turbine engine exhaust system

Abstract: A thrust vectoring gas turbine engine exhaust nozzle is provided with a variable area flow path wherein cooling of the stationary flow path side walls is partially obtained by the film cooling technique. Regulating means, such as a valve, is provided to control the pressure drop of the cooling fluid across the walls as a function of nozzle flow path area, thus optimizing the coolant flow rate as a function of flow path area. Where a rotating bonnet-type deflector is employed to divert the exhaust stream downward to obtain a vertical take-off and landing capability, a system is provided to cool the deflector walls by both the impingement and convection cooling techniques. A favorable pressure gradient for the cooling fluid is obtained by exhausting the cooling fluid to ambient pressure whenever the deflector is deployed. Another valve is provided to regulate the flow of coolant to an expansion flap when the deflector is in its stowed position external to the flow path.