Showing papers on "Pressure drop published in 1982"

An infinite-series solution for the creeping motion through an orifice of finite length

Abstract: This paper presents an infinite-series solution to the creeping viscous motion of a fluid through low- and moderate-aspect-ratio pores. The flow field is divided into two simply bounded regions: a cylindrical volume bounded by the walls of the pore and the entrance and exit planes, and an infinite half-space outside the pore. Analytic solutions are first obtained in each region for unknown functions representing arbitrary axial and radial velocity profiles at the pore entrance (exit). These unknown functions are then determined by matching the normal and tangential stress at the pore opening.The results indicate that the velocity profile approaches to within 1·5 per cent of a Poiseuille profile after a short entrance distance of half the pore radius. In the far field the solution matches exactly the streamline pattern for a flow through an orifice of zero thickness obtained by Sampson (1891). The pressure drop across the pore exhibits linear dependence on the aspect ratio and is closely approximated (less than one per cent error) by a simple algebraic expression.

Systems, apparatus and methods for measuring while drilling

Abstract: This invention is concerned with downhole measurements while drilling a borehole in the earth with a drill bit at the lower end of the drill string and transmitting such measurements to the surface. The drilling fluid is forced through a fluid passage which includes a drill string, a bit at the lower end thereof and the annulus surrounding the drill string. There is a restriction in the passage causing a pressure drop creating a high pressure zone and a low pressure zone within said passage, and a drilling fluid bypass comprising a bypass valve provides fluid communication between the high pressure zone and the low pressure zone. By means of a downhole sensor and associated equipment a plurality of pulse or electrical voltage change signals representing downhole information is produced. Each of these signals is arranged to generate several electrical voltage changes. A control means is provided to cause opening of the bypass valve responsive to one of these signals and for causing closing of the valve responsive to another of said signals.

Mechanics of Turbulent Buoyant Jets and Plumes

Abstract: The mechanics of submerged turbulent jets has received a good deal of research attention. This work has resulted in an understanding of the process by which jets grow by entrainment of surrounding fluid. While of direct scientific interest, this work has practical implications that are of interest to engineers concerned with the design of systems that utilize jet concepts. A fluid motion is called a jet if its primary source of kinetic energy and momentum flux is a pressure drop through an orifice. A fluid motion whose main source of kinetic energy and momentum flux is body forces is called a plume. The flows, whose motion is in transition from a jet to a plume, are called a forced plume or a buoyant jet. Almost all jets whose fluid density differs from the ambient fluid density become plumes. This chapter discusses the mechanics of jets and plumes whose interactions with their environment are self-generated. It discusses how such jets and plumes are influenced by changes in the environment such as density stratification of the surrounding fluid, uniform motion of the ambient fluid, or turbulence within the ambient fluid.

Local drag reduction due to injection of polymer solutions into turbulent flow in a pipe. Part I: Dependence on local polymer concentration

Abstract: Aqueous solutions of drag-reducing polymers were injected into turbulent water flow in a pipe. The injection point was situated where the flow was well-developed. Thus, subsequent streamwise variations in pressure drop were due to the injected polymer spreading out across the pipe. The axial development of local drag reduction was monitored by a series of closely-spaced pressure tappings. The corresponding radial dispersion of the injected polymer, as it travelled downstream, was assessed by sampling the flow at various points. Local drag reduction, due to either point injection at the centerline or injection through a slot in the wall, was found to increase with distance downstream. This increase was related to the streamline increase of polymer concentration in a narrow annulus near the pipe wall. It was tentatively concluded that the effective annulus was bounded by 15 less than or equal to y + greater than or equal to 100, in agreement with previous deductions from less direct evidence.

Plate type heat exchanger tube pass

Abstract: A fluid tube pass for a heat exchanger formed by a pair of plate members which have their edge portions joined together to form a refrigerant enclosure between plate midportions for flow. Fluid inlet and outlet manifolds are formed at either plate end by drawn, outwardly offset configurations. Between the manifolds, rows of separated ribs are similarly formed, each rib angled obliquely to the flow path between the manifolds and each row extending transversely normal to the flow path. The ribs in each row are staggered and overlap other ribs in the direction of flow to prevent linear flow across all the transverse rows between the inlet manifold and the outlet manifold but provide an interrupted linear flow path or by-pass across the middle of the transverse rows in addition to by-pass flow paths past the ends of the rows to improve heat transfer efficiency without substantially increasing pressure drop.

Two-Way Coupling Effects in Dilute Gas-Particle Flows

Abstract: A general analysis of gas-particle flows is presented using the hypotheses of a number of particles large enough to consider the solid phase as a continuum and of a volume fraction small enough to consider the suspension as dilute. It is found that the Stokes number (Sk) and the particle loading ratio (beta) are the basic parameters governing the flow. For small values of beta and large values of Sk it is possible to disregard the effect of the particles on the fluid field and simple numerical models based on one-way coupling may be used. However, for larger values of beta and lower Sk, both the fluid and the solid phase flow fields (and as a consequence the overall quantities such as pressure drop and energy dissipation) are determined to be substantially affected by the interphase coupling. A computational model accounting for two-way coupling is presented and found to provide for an accurate simulation. In addition, correlations are developed for determining the pressure drop which increases as a function of beta and Sk, and it is suggested that these correlations may be of practical interest for the investigation of flow metering systems.

Measurement of air mass flow into an internal combustion engine

Abstract: An air mass flow measuring system for measuring flow into an internal combustion engine comprises a throttle angle transducer and further transducers measuring ambient air temperature and pressure as well as the pressure drop across the throttle valve. The signals from these transducers are supplied to calculating circuit which carries out the calculation M=K√P·ΔP/T. The values of the coefficient K used in this calculation are derived from an empirically programmed read only memory incorporated in the calculating circuit, such memory storing empirically determined values of K for each combination of a plurality of values of throttle angle and a plurality of values of √ P·ΔP/T.

Flow of dilute polymer solutions through converging channels

Abstract: Extensional motion of non-Newtonian fluids was studied by pushing dilute solutions of polyethylene oxide through miniature converging channels. The channels were conical or smoothly converging in shape, and each had an exit diameter around 0.13 mm to make Reynolds number effects comparable. Channels were also made by cementing small beads together, which created passages similar to those in packed beds. Pressure drop and flow rate were measured in each channel and the flow field was observed. Flow patterns and data for the solutions were the same as for water when the maximum rate of extension was below about 103 s−2. Above this, the pressure drop for a solution exceeded that of water, and when solution values reached twice the water values, the flow pattern changed abruptly from a simple converging motion to one dominated by a large unsteady vortex ring surrounding the channel opening on the upstream side. This secondary motion persisted at high flow rates, had a variety of forms, and at times produced tiny filaments of polymer, most likely by strain-induced crystallization. Non-Newtonian effects were found to increase with concentration and to decrease with temperature and ago; in each case, much of the effect could be traced to that parameter's influence on the onset of non-Newtonian behaviour. In bead channels with successive convergent sections, onset strain rates were much lower, around 102 s−1, indicating that strain history has a strong effect on onset. Disparate onset strain rates for the various single channels, from 300 s−1 to 6000 s–1, were accounting for by considering total extension of the polymer molecules in each flow. In fact, analyses suggest that molecules were stretched about six times their coil size in the converging flows. The large non-Newtonian effect when secondary motion is present is thought to result from high molecular extension or possibly from a contraction of the central flow.

Peristaltic Transport of a Power-Law Fluid With Variable Consistency

Abstract: Effects of the consistency variation on the peristaltic transport of a non-Newtonian power-law fluid through a tube have been investigated by taking into account the existence of a peripheral layer. It is shown that the flow rate flux, for zero pressure drop, increases as the amplitude of the peristaltic wave increases but it decreases due to the pseudoplastic nature of the fluid. It is also noted that, for zero pressure drop, the flux does not depend on the consistency of peripheral layer while the friction decreases as this consistency decreases. However, for nonzero pressure drop, the flux increases and the friction force decreases as the consistency of peripheral layer fluid decreases.

Friction pressure drop and heat transfer coefficient of two-phase flow in helically coiled tube once-through steam generator for integrated type marine water reactor.

Abstract: Two-phase friction pressure drop and heat transfer coefficients in a once-through steam generator with helically coiled tubes were investigated with the model test rig of an integrated type marine water reactor. As the dimensions of the heat transfer tubes and the thermal-fluid conditions are almost the same as those of real reactors, the data applicable directly to the real reactor design were obtained. As to the friction pressure drop, modified Kozeki's prediction which is based on the experimental data by Kozeki for coiled tubes, agreed the best with the experimental data. Modified Martinelli-Nelson's prediction which is based on Martinelli-Nelson's multiplier using Ito's equation for single-phase flow in coiled tube, agreed within 30%. The effect of coiled tube on the average heat transfer coefficients at boiling region were small, and the predictions for straight tube could also be applied to coiled tube. Schrock-Grossman's correlation agreed well with the experimental data at the pressures of lower ...

Thermal Energy Storage in Phase Change Material.

Abstract: : The present study deals with an experimental investigation of low temperature thermal storage based on macroencapsulation of Phase Change Material (PCM). The storage performance capabilities of capsule bed, tube bank and tubular single-pass heat exchanger are compared. The tests are conducted on the VKI Solar Utility Network (SUN) which is a closed loop facility designed to study air heating systems. An original data acquisition chain based on two conversing microprocessors is developed to carry out mass flow, pressure drop and temperature measurements. The experimental results are interpreted on the basis of comparison with numerical predictions and they allow to draw the following conclusions. Each type of matrix has its own range of operation for practical application but from a heat transfer standpoint, the PCM capsule packing unit is strongly recommended. It is suggested to extend this investigation to the effect of Reynolds number to find optimum range for thermo-mechanical efficiency.

Laminar and turbulent flows of dilute polymer solutions: a physical model

Abstract: It is well known that diluted high-molecular polymer solutions give rise to drastic flow effects; for example, in laminar flow through porous media, a pressure drop increase of up to thirty times the value of the flow of the pure solvent is observed, whereas in turbulent wall bounded flow, a pressure drop decrease or drag reduction of up to 80% or five times lower than the Newtonian value is measured. Although both these dramatic influences on the flow are caused by the same polymers, dissolved in the same solvent and employed in the same concentration range, the effects are usually interpreted by different models in the literature. The reason for this is the apparent contrariety of the observed polymer effects in laminar and turbulent flows.

Analysis of vertical pneumatic conveying of solids using multiphase flow models

Abstract: The multiphase flow models were used to predict pressure drop and segregation of particles flowing in a vertical pipe. To compare calculations with data, it was necessary to assume an effective particle size based on a coefficient of restitution and on inlet void fractions. Different partifle size distributions with equal average particle size generate distinctly different pressure drops and segregations. Contribution of solid interaction force is very important in accounting for the segregation of the particles in a vertical pipe. All models gave a reasonable prediction of the design parameters. The pressure drops predicted by the models agreed well with both high- and low-pressure experiments.

High speed turbogenerator for power recovery from fluid flow within conduit

Abstract: A high speed turbogenerator functionally combining, in one machine, an electrical generator and an expansion turbine. The electrical generator itself has a shaft supported on two bearings and the expansion turbine comprises an expander wheel overhung on the generator shaft and which rotates as a high pressure gas is let down in the expansion turbine to a lower pressure at a minimum predetermined flow rate and pressure drop. The shaft operates at speeds of about 6,000 rpm to 32,000 rpm, preferably at the higher end of such range, i.e. 20,000 to 24,000 rpm. The unit is sufficiently compact that a new use for the electrical generator is to modify the same such that the entire high speed turbogenerator is contained within the conduit carrying the gas to be let down in pressure and only electrical wires need be led through the conduit. The integrity of the conduit is thus retained to the extent possible and only a high pressure cable fitting extends through the conduit. In the preferred embodiment, the high speed turbogenerator is entirely fitted within a natural gas conduit in a gas distribution station, thereby achieving the pressure letdown and also obtaining useful electrical power.

Steady Expiratory Flow-Pressure Relationship in a Model of the Human Bronchial Tree

Abstract: Static pressure differences across a human bronchial tree model were obtained for steady expiratory flows of several gases producing Reynolds numbers (Re1) in the bronchus carrying the entire flow (first bronchus) between 150 and 50,000. The model was constructed from an air-dried lung and was complete to bronchi about 2 mm in diameter. Dimensionless static pressure plotted against Re1 consolidated the data on a single curve, phenomenologically described by an equation of the form: delta Ps/delta Pd1 = A + B Re1 where delta P d1 is a pressure drop for Poiseuille flow, Velocity profile measurements at two sites along the first bronchus for laminar and turbulent flows indicate a dependence on the latter and distance from the first junction. Loss in total pressure was computed and may result from both frictional dissipation and changes in momentum flux associated with development of velocity profiles near the junctions. An average loss in total pressure within a single bronchus was calculated after making several simplifying assumptions, and this result may be useful in modeling both the resistance of the entire bronchial tree and the more complex phenomenon of maximal expiratory flow.

Backwash control for constant volume-pressure filtration system

Abstract: In a system having a fluid filter that is automatically backwashed each time the differential pressure thereacross reaches a predetermined value, the desired base rate at which the drop across the filter should increase during its initial filtering sequence (i.e., before backwash) is determined and stored in digital format in a process controller along with a preset maximum differential pressure at which backwash is set to occur. During use of the filter the actual rate of change of the pressure drop thereacross is monitored continuously and compared with the rate that is stored in the controller. Whenever the actual rate of change of the pressure drop across the filter differs from the base rate, which is the usual case, the present backwashing pressure is automatically adjusted--usually downwardly. This reduction continues until the actual drop across the filter finally reaches the adjusted value of the preset backwashing pressure, at which time backwashing of the filter is automatically commenced. In a preferred embodiment, the adjustment is based upon the time differential at a given instant between the actual filter time and the desired or base curve time, and the difference is used to reduce the preset pressure in accordance with the inverse of the base curve rate. In another embodiment the difference between the actual differential pressure across a filter and the desired differential pressure at any instant is determined and subtracted from the preset backwashing pressure.

Pressure drop and homogenization efficiency of a motionless mixer

Abstract: Pressure drop and homogenization efficiency of a motionless mixer of helical type have been studied experimentally. For evaluation of the drag coefficient the equation has been proposed which is valid within the range of Reynolds number from 10−2 to 104 The efficiency of the motionless mixer for mixing of two Newtonian liquids has been investigated by using a decolourization method. For the operating conditions studied in this work it appears that there is the worse performance of the mixer about the Reynolds number of 50. No influence of volume flow rate ratios (from 1 to 10) upon the performance of the mixer has been observed. A higher number of mixing elements must be applied for homogemzation of liquids with viscosity ratios above 100 as compared with that for viscosity ratio 1.

Apparatus and method for testing containers

Abstract: A method and apparatus for testing containers for pressure leak characteristics is disclosed. The arrangement includes monitoring the fluid pressure in a container supplied with test fluid at two different time intervals, with the monitored difference being compared with a predetermined acceptable value of container pressure loss and a signal generated to either accept or reject the tested container. To facilitate a continuous updating of the calibration of the acceptable pressure loss, a digital computer controlled arrangement is provided for adjusting the predetermined acceptable pressure loss value as a function of the monitored difference in the pressures for containers previously tested.

Liquid-level measuring system

Abstract: MEASURING SYSTEM LEVEL OF A LIQUID IN A TANK FOR EXAMPLE THE WATER LEVEL IN BOILER WITH TWO PRESSURE SENSORS BELLOWS 18, 20 MONTES IN BOILER OF DIFFERENT LEVELS RESPECTIVELY THE LIMITS THEREOF LOWER AND UPPER L2, L3 BEACH VARIATION LEVEL L1 LIQUID BOOTS 24, 24 bEING FILLED FLUID AND CONNECTED BY A PIPE VERTICAL 70 AND MOVEMENT SENSOR 62 BELLOWS LOWER 24 PROVIDING AN ELECTRICAL SIGNAL PROPORTIONAL PRESSURE DIFFERENCE BETWEEN THE TWO BOOTS, SO THE WATER LEVEL IN THE BOILER TO PREVENT oVERHEATING THE REFERENCE IN THE LINE COLUMN 70 AND DESTRUCTION OF POSSIBLE BELLOWS 24, 24 IN SUCH THAT 350C TEMPERATURE AND PRESSURE 15 BARS, FLUID REFERENCE COMPRISES AN INSTRUCTOR SUBSTANCE LIQUID, AS NAK REMAINS IN LIQUID PHASE VERY HIGH TEMPERATURES EVEN THERE PRESSURE DROP IN THE BOILER NAK BEING EXTREMELY REACTIVE WITH WATER, BELLOWS 24, 24 ARE MOUNTED IN A SEALED ENVELOPE 26, 26 FILLED SUBSTANCE INERTE, SUCH AS ALLOY SnPb, SOLID STATE ROOM TEMPERATURE AND LIQUID PHASE FROM 86C, THIS ENVELOPE WITH A bELLOWS OUTSIDE 34, 34 FILLED WITH THE SAME SUBSTANCE IN COMMUNICATION WITH THE INTERIOR 46 50 ENVELOPE