Fluid velocities in piping

Suggested Fluid Velocities in Pipe and Tubing (Liquids, Gases, and Vapors at Low Pressures to SOpsig and 50°F-100°F)... 

The above model assumes complete suspension of the particles. Fluid velocities in pipes of 1 m/s are ample for suspension of typical solid alkali reagents. Typical agitation intensities of around. 2 W/kg are adequate for suspension of typical calcium hydroxide preparations in tanks. 

Gup and Vane Anemometers. A number of flow meter designs use a rotating element kept in motion by the kinetic energy of the flowing stream such that the speed is a measure of fluid velocity. In general, these meters, if used to measure wind velocity, are called anemometers if used for open-channel Hquids, current meters and if used for closed pipes, turbine flow meters. 

Particles of fluid flowing in pipes act in the same manner. The flow is streamlined if the fluid flows slowly enough, and remains streamlined at greater velocities if the diameter of the pipe is small. If the velocity of flow or size of pipe is increased sufficiently, the flow becomes turbulent. 

Fluid velocities in the piping to the riser and riser are held in the 2 to 4-fps range. 

In the reactor, the liquid/vapor interface is a corrosion-prone area. This section can be strengthened by attaching a sacrificial plate to the liner. Reactor outlet piping and let-down valves are subjected to erosion corrosion from the pressure reduction across the valve and from high fluid velocities in pipelines88. 

The kinetic-energy terms of the various energy balances developed h include the velocity u, which is the bulk-mean velocity as defined by the equati u = m/pA Fluids flowing in pipes exhibit a velocity profile, as shown in Fi 7.1, which rises from zero at the wall (the no-slip condition) to a maximum the center of the pipe. The kinetic energy of a fluid in a pipe depends on actual velocity profile. For the case of laminar flow, the velocity profile parabolic, and integration across the pipe shows that the kinetic-ertergy should properly be u2. In fully developed turbulent flow, the more common in practice, the velocity across the major portion of the pipe is not far fro... 

For the conditions indicated in Prob. 7, prepare a log-log plot of fluid velocity in feet per second versus optimum economic pipe diameter in inches. The plot should cover a fluid-velocity range of 1 to 100 ft/s and a pipe-diameter range of 1 to 10 in. 

Substituting Equations 8.10 and 8.11 into Equation 8.9 and solving for the fluid velocity in the pipe, we find that... 

The velocity u in the kinetic-energy terms of energy balances is tire bulk-mean velocity as defined by the equation, u = Fluids flowing in pipes exlribit a velocity profile, as... 

Mixer in tank drop diameter 4 to 5000 pm capacity >0.05 L/s for viscosities <10 mPa-s. Colloid mill drop diameter 1 to 8 pm capacity 0.01 to 3 L/s for viscosities <10 mPa s but usually >1000 mPa-s. Homogenizer drop diameter 0.1 to 2 pm capacity 0.03 to 30 L/s for viscosities <10 mPa s but usually <200 mPa-s decrease the drop diameter by increasing the exit pressure. High shear disperser for viscosities 10 to 5 x 10 mPa s. Roller mills for viscosities >10 mPa-s. Motionless mixer drop diameter 100 to 1000 pm (about 0.15 times drop diameter for fluid velocity in a pipe... 

Dimensionless velocity quotient, / /, at pipe axis Average fluid velocity in x direction Pj, at stations a and b Pump work, J/kg or ft-lbj-/lb Radial distance from pipe wall, ra or ft Dimensionless distance, y, at pipe axis... 

Gas-law constant, 8.314 N-m/gmol-K or 1545 ft-lbj-/lb mol- R Radius, m or ft r, of impeller at suction r2, of impeller at discharge Cross-sectional area, m or ft Sf, of venturi throat S , of orifice Absolute temperature, K or °R T, at compressor inlet 7, at compressor dicharge also torque, J or ft-lbf Local fluid velocity, m/s or ft/s maximum velocity in pipe Ug, at orifice Uq, at impact point of pitot tube Uj, peripheral velocity at inlet of pump impeller Hj, at impeller discharge Waj, Ho2) tangential velocity components at stations 1 and 2 Resultant velocity, absolute, in pump impeller, m/s or ft/s Vr2,... 

Besides clarifying the strange shape of Fig. 6.2, Reynolds made the most celebrated application of dimensional analysis (Chap. 13) in the history of fluid mechanics. He showed that for smooth, circular pipes, for all newtonian fluids, and for all pipe diameters, the transition from laminar to turbulent flow occurs when the dimensionless group DVpIfjt, has a value of about 2000. Here D is the pipe diameter, V is the average fluid velocity in the pipe, p is the fluid density, and fi is the fluid viscosity. This dimensionless group is now called the Reynolds number For flows other than pipe flow, some other appropriate length is substituted for the pipe diameter in the Reynolds number, as discussed later. 

Figure 2.5 Distribution profiles of perforated pipe distributors.fa) Ideal distribution (b) excessive fluid velocity through pipe (c) same as for b, but with column vapor sucked in (d) insufficient perforation pressure drop (e) severe hydraulic disturbance near pipe inlet.

Pressure drop in helical coils is dependent on whether the flow is laminar or turbulent. Typically flows are laminar at low fluid velocities and turbulent at high fluid velocities. In cuived pipes and coils a secondary circulation takes plac e called the double eddy or Dean Effect. VVliile this circulation increases the friction loss, it also tends to stabilize laminar flow, thus increasing the critical Reynolds number. 

Static mixer drop diameter 100-1000 pm (about 0.15 times drop diameter for fluid velocity in a pipe without the mixer) capacity 0.3-5 L/s. The densities and flowrates of the two phases should be about equal viscosities < 50 mPa s. See also Section 6.6. 

Since the annulus fluid velocity in the cross section is not the same, generally the velocity in the middle part of the drilling fluid is higher, carrying the particles back. And the velocity on both sides close to the drill pipe and the borehole fluid flow area is lower, making it difficult for the particles to be carried back. Therefore, the particle settling velocity Vp multiplied by the correction... 

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