Maximum line velocity

Because of the reciprocating action of the piston, care must be exer-ci.sed to size the piping to minimize acoustical pulsations and mechanical vibrations. As a rule of thumb, suction and discharge lines should be sized for a maximum actual velocity of 30 ft/.sec (1,800 ft/min) to 42 ft/sec (2,500 ft/min). Volume 1 contains the necessary formulas for determining pressure drop and velocity in gas piping. 

In lines carrying saturated steam, reasonable maximums for velocities are often taken at up to 40 m/s in larger pipes... 

Data for the bulk fluid, line A, indicate that vz varies as a function of z but maintains a value near 0.75 of maximum velocity. The periodicity of vx and vy is clearly evident in the graph of line A and a 1800 out of phase coupling of the components is seen with one positive when the other is negative. This indicates a preferred orientation to the plane of the oscillatory flow and this feature was seen in all the biofilms grown throughout this study. The secondary flow components are 0.1-0.2 of the maximum axial velocity and are spatially oscillatory. The significant non-axial velocities indicate non-axial mass transport has gone from diffusion dominated, Pe = 0, in the clean capillary, to advection dominated, Pe 2 x 103, due to the impact of the biofilm. For comparison, the axial Peclet number is Pe L 2x 10s. Line B intersects areas covered by biomass and areas of only bulk... 

Also referred to as the Hanes-Hultin plot and the Hanes-Woolf (or, Woolf-Hanes) plot, the method is based on a transformation of the Michaelis-Menten equation i.e., the expression for the Uni Uni mechanism) [A]/v = (i a/ max) + ([A]/Umax) whcrc U ax IS the maximum forward velocity and is the Michaelis constant for A. In the Hanes plot, the slope of the line is numerically equal to Umax, the vertical intercept is equivalent to, ... 

It is interesting to compare the assumptions made by Bankoff to the restrictions operating in the investigation by Nicklin, Wilkes, and Davidson for slug flow. In their work the velocity component of the slugs due to liquid flow approached the maximum liquid velocity at the tube center-line. If this is also true of the bubbles of Bankoff s model and the bubble rise velocity due to buoyancy is ignored, then the velocity of the bubbles as given by Nicklin et al. would be,... 

Figure 6, which is for the same simulation as Fig. 4, shows sectional averages of the pressure, particle velocity, and density as a function of position with the dashed lines denoting the initial values in the undisturbed crystal. These quantities peak at the front and then relax during the reaction and expansion behind the shock. The shockfront shape is in accord with ZND continuum theory for unsupported planar detonations, which predicts a von Neumann peak near the front followed by a reacting flow and a (Taylor) rarefaction wave. The peak pressure around 1.0 eV/A (Fig. 6, top), which corresponds to an effective pressure of approximately 400 kbar, and maximum particle velocity of 4.8 km/s (Fig. 6, middle) are consistent... 

The characteristics and complexity of flow pattern are such that most flows are described by a set of empirical or semi-empirical equations. These relate the pressure drop in the flow system as a function of flow rate, pipe geometry, and physical properties of the fluids. The aim in the design of fluid flow is to choose a line size and piping arrangement that achieve minimum capital and pumping costs. In addition, constraints on pressure drop and maximum allowable velocity in the process pipe should be maintained. These objectives require many trial and error computations, which can be performed well by a computer. 

The mucociliary escalator functions when inhaled particles between 2 to 10 pm are deposited on the sticky mucous lining of the tracheobronchial tree and are propelled upward by the movement of this mucous layer in response to the beat of the cilia on the ciliated epithelial cells. This phenomenon is made possible because the mucous layer is biphasic, consisting of a watery solution in direct contact with the epithelia cells in which the cilia are free to beat. This watery solution is covered by a stickier, more adhesive gel layer that can trap and hold inhaled particles. The cilia beat in the wall layer at a rate between 1000 and 1500 strokes per minute such that at the point of their maximum upward velocity, the tips of the cilia come in contact with the gel layer to propel it upward. All recovery strokes subsequently occur in the water layer. This mechanism moves the mucus upward at a rate between 1 and 3 cm/minute. Ultimately, the mucus reaches the pharynx, where it is swallowed. Disease states that either alter the mucus-producing properties of cells in the tracheobronchial tree or decrease ciliary activity will obviously have a deleterious effect on this important clearance mechanism. 

FIGURE 19 Lower figure Newton diagram for H-i- D2 reaction. Circles show maximum CM velocities for differerent rotational levels of HD (v = 0) products. Upper figure D atom laboratory angular distribution solid line shows theoretical simulation. (From Casavecchia, R, Balucani, N., and Volpi, G. G. (1999). Annu. Rev. Phys. Chem. 50, 347-376.)... 

The pressure drop in vapor piping should be very low. What is considered a reasonable line loss in a pressurized system can be a substantial fraction of the absolute pressure needed at the source. Line velocities also should be limited. At typical dechlorination system pressures, a maximum of 45 m s is desirable. With evaporators operating below lOkPa, 55 m s is more typical. 

The rationale for using Up as the relevant relative velocity is that this represents the maximum relative velocity that would be experienced by the particle as it attempts to continue in a straight line. 

Reynolds also found that the dye streams velocity was the same for a given radial distance from the tube center (or wall). Hence, at a particular circumference the velocity had the same value. Furthermore, he found that the maximum fluid velocity occurred at the tube s center line and then decreased as the radius approached the radius of the tube wall. 

For the transfer tests and liquid acquisition systems, COLD-SAT parameters from all four studies are compiled in Table A.2. Wherever parameters were not readily available, assumptions were made to derive those parameters. For example, MEOPs were determined from the anticipated maximum ranges of tank pressures during pressurization/ outflow tests. Flow rates were determined from LAD or no vent fill (NVF) subsystem requirements. Re numbers in the transfer line were determined based on total flow delivery from the LAD subsystem and the internal diameter of the pipe. Line velocities were determined using conservation of mass. 

Both the calculated and measured values of the axial velocity are smaller and the location of the maximum raditil velocity gets closer to the contact line in the case of two-liquid systems than in the air/liquid case due to the higher viscosity of the receding phase (fig. 6) compared to the system of figure 5. This is shown in the flow patterns, too. 

Figure 8 shows the pressure fields in dry contact, fiill film and mixed film lubrication, for point A of the meshing line (initial engagement point - wheel head / pinion root, Ve=0.65) of the FZG type C gear. The wheel speed is 2100 rpm (pitch line velocity of 12 m/s) for load stage 9 (maximum Hertzian pressure of 1.4 GPa at pitch point). 

Aqueous hydrogen fluoride of greater than 60% maybe handled in steel up to 38°C, provided velocities are kept low (<0.3 m/s) and iron pickup in the process stream is acceptable. Otherwise, mbber or polytetrafluoroethylene (PTFE) linings are used. For all appHcations, PTFE or PTEE-lined materials are suitable up to the maximum use temperature of 200°C. PTEE is also the material of choice for gasketing. AHoy 20 or Monel is typically used for valve and pump appHcations. Materials unacceptable for use in HE include cast iron, type 400 stainless steel, hardened steels, titanium, glass, and siHcate ceramics. 

Pipe-hue pumping stations usually range from 16 to 160 km (10 to 100 miles) apart, with maximum pressures up to 6900 kPa (1000 Ibf/ in") and velocities up to 3 m/s (10 ft/s) for liquid. Gas pipe lines have higher velocities and may have greater spacing of stations. 

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