Fluid flow velocity

Valves, see pipe, fittings, and valves Vapor cloud explosions, 520 Velocities, fluid flow, 85, 89, 90 Vacuum lines, 133 Velocity head, 71... 

Above 93°C (200°F) Greater than 15 % acid with >1000 ppm F and Very high velocity fluid flow with impingement of >10 000 ppm Cl , or intermittent wet/dry entrained particulates (e.g., venturi throat) zones ... 

Cross-flow velocity Fluid flow at right angles to a heat-transfer tube. 

The reason for the previously mentioned phenomena is that PAM fluid is a viscous-elastic fluid when it is in movement, there is a normal force pointing to the direction of the high-velocity fluid flow. Centrifugal pumps rotate at a high speed to produce centrifugal force to pump the fluids out of the well when pumping PAM fluids, besides the centrifugal force, there is also a normal... 

The continuous formation and collapse of numerous bubbles at the surface of a component, created due to localized pressure changes during high-velocity fluid flow, could lead to cavitation erosiom Collapse of these bubbles is always accompanied by the emission of shockwaves and micro-jets, which will exert stress pulses on solid surfaces in the vicinity. Repetitions of shockwaves on the solid surface will eventually lead to fatigue failure, fracture and material loss (Brennen, 1995 Kwok et ai, 2000). Cavitation erosion is commonly observed in valves in nuelear power plants and in pumps in the petroleum industiy. Cavitation erosion is essentially a mechanical process. However, in many working environments, eavitation erosion and eorrosion occur simultaneously, and if eorrosion does oeeur it will accelerate the rate of eavitation erosion damage. 

Oil viscosity is an important parameter required in predicting the fluid flow, both in the reservoir and in surface facilities, since the viscosity is a determinant of the velocity with which the fluid will flow under a given pressure drop. Oil viscosity is significantly greater than that of gas (typically 0.2 to 50 cP compared to 0.01 to 0.05 cP under reservoir conditions). 

For a single fluid flowing through a section of reservoir rock, Darcy showed that the superficial velocity of the fluid (u) is proportional to the pressure drop applied (the hydrodynamic pressure gradient), and inversely proportional to the viscosity of the fluid. The constant of proportionality is called the absolute permeability which is a rock property, and is dependent upon the pore size distribution. The superficial velocity is the average flowrate... 

The purpose of the well completion is to provide a safe conduit for fluid flow from the reservoir to the flowline. The perforations in the casing are typically achieved by running a perforating gun into the well on electrical wireline. The gun is loaded with a charge which, when detonated, fires a high velocity jet through the casing and on into the formation for a distance of around 15-30 cm. In this way communication between the wellbore and the reservoir is established. Wells are commonly perforated after the completion has been installed and pressure tested. 

A low Reynolds number indicates laminar flow and a paraboHc velocity profile of the type shown in Figure la. In this case, the velocity of flow in the center of the conduit is much greater than that near the wall. If the operating Reynolds number is increased, a transition point is reached (somewhere over Re = 2000) where the flow becomes turbulent and the velocity profile more evenly distributed over the interior of the conduit as shown in Figure lb. This tendency to a uniform fluid velocity profile continues as the pipe Reynolds number is increased further into the turbulent region. 

Flow nozzles are commonly used in the measurement of steam and other high velocity fluids where erosion can occur. Nozzle flow coefficients are insensitive to small contour changes and reasonable accuracy can be maintained for long periods under difficult measurement conditions that would create unacceptable errors using an orifice installation. 

Measurement Applications. Lasers have been used for measurement of many physical parameters. These include length and distance, velocity of fluid flow and of soHd surfaces, dimensions of manufactured goods, and the quaHty of surfaces, including flaw detection and determination of... 

A final example of laser measurement techniques is measurement of the velocity of fluid flow (79) (see Flow measurement). If a laser beam is directed into a transparent fluid, some of the light may be scattered with a frequency shift zy given by... 

Fig. 4. (a) Photographs of fluid flow behind cylinders at increasing flow velocities top to bottom, (b) Photomicrographs of nickel—nickel bond 2ones made at increasing coUision velocities top, 1600 m/s middle, - 1900 m/s bottom, - 2500 m/s (23). 

The flow resistance of pipe fittings (elbows, tees, etc) and valves is expressed in terms of either an equivalent length of straight pipe or velocity head loss (head loss = Kv /2g ). Most handbooks and manufacturers pubHcations dealing with fluid flow incorporate either tables of equivalent lengths for fittings and valves or K values for velocity head loss. Inasmuch as the velocity in the equipment is generally much lower than in the pipe, a pressure loss equal to at least one velocity head occurs when the fluid is accelerated to the pipe velocity. 

Bellows can vibrate, both from internal fluid flow and externally imposed mechanical vibrations. Internal flow liner sleeves prevent flow-induced resonance, which produces bellows fatigue failure in minutes at high flow velocities. Mechanically induced resonant vibration is avoided by a bellows with a natural frequency far away from the forcing frequency, if known. Multiple-ply bellows are less susceptible to vibration failure because of the damping effect of interply friction. 

A positive value iadicates vertical movement. Thea, moving from the outer wall to the air core, the axial velocity iacreases to positive values. Thus, the fluid motioa is dowa the wall of the cycloae to the apex and up the air core through the vortex finder. In the cylindrical section, the axial velocity goes negative again, approaching the vortex-finder wall. The fluid flow is then down the inner cyclone wall and the outer vortex-finder wall. There is a locus of zero axial velocity. 

The particle size deterrnined by sedimentation techniques is an equivalent spherical diameter, also known as the equivalent settling diameter, defined as the diameter of a sphere of the same density as the irregularly shaped particle that exhibits an identical free-fall velocity. Thus it is an appropriate diameter upon which to base particle behavior in other fluid-flow situations. Variations in the particle size distribution can occur for nonspherical particles (43,44). The upper size limit for sedimentation methods is estabHshed by the value of the particle Reynolds number, given by equation 11 ... 

Example 1 Force Exerted on a Reducing Bend An incompressible fluid flows through a reducing elbow (Fig. 6-5) situated in a horizontal plane. The inlet velocity Vj is given and the pressures pi and measured. 

Example 4 Plnne Poiseuille Flow An incompressible Newtonian fluid flows at a steady rate in the x direction between two very large flat plates, as shown in Fig. 6-8. The flow is laminar. The velocity profile is to he found. This example is found in most fluid mechanics textbooks the solution presented here closely follows Denn. 

This subsertion deals with the techniques of measuring pressures, temperatures, velocities, and flow rates of flowing fluids. 

Fluid-Elastic Coupling Fluid flowing over tubes causes them to vibrate with a whirling motion. The mechanism of fluid-elastic coupling occurs when a critical velocity is exceeded and the vibration then becomes self-excited and grows in amplitude. This mechanism frequently occurs in process heat exchangers which suffer vibration damage. 

T) Venturimeter - To measure the velocity of fluid Probe to sense the velocity of fluid Flow meter or sensor - To convert the velocity of fluid to the rate of flow... 

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