Pipeline velocities

When vapor flows through a tray deck, the vapor velocity increases as the vapor flows through the small openings provided by the valve caps, or sieve holes. The energy to increase the vapor velocity comes from the pressure of the flowing vapor. A common example of this is the pressure drop we measure across an orifice plate. If we have a pipeline velocity of 2 ft/s and an orifice plate hole velocity of 40 ft/s, then the energy needed to accelerate the vapor as it flows through the orifice plate comes from the pressure drop of the vapor itself. 

The rapid methods. Fig. 6.13 and App. A.4, are of no use in this case, because the flow velocity is much larger than normal pipeline velocities. Ignoring the kinetic energy of the exit fluid, or the friction loss in the pipCj or the entrance loss would have given a significantly incorrect answer. 

Figure 4.30 Stepped pipeline velocity profile for high pressure dilute phase system.

Figure 19-4 Pipeline velocity requirements with different mixers.

Mixing Minimum Pipeline Velocity, meters per second ... 

Tracer Type. A discrete quantity of a foreign substance is injected momentarily into the flow stream and the time interval for this substance to reach a detection point, or pass between detection points, is measured. From this time, the average velocity can be computed. Among the tracers that have historically been used are salt, anhydrous ammonia, nitrous oxide, dyes, and radioactive isotopes. The most common appHcation area for tracer methods is in gas pipelines where tracers are used to check existing metered sections and to spot-check unmetered sections. 

Other Flow Straightening Deviees Other devices designed to produce uniform velocity or reduce swirl, sometimes with reduced pressure drop, are available. These include both commercial devices of proprietaiy design and devices discussed in the hterature. For pipeline flows, see the references under flow inverters and static mixing elements previously discussed in the Tncompressible Flow in Pipes and Channels subsection. For large area changes, as at the... 

Since the predicted droplet diameter at high velocity pipeline flow varies with (LVelocity) ", as shown by Eq. (14-201), the volumetric performance is strongly dependent on velocity ... 

The ] atio of the I rns velocity fluctuation to the avei age velocity in the irnpelle] zone is about 50 pei cent with many open irnpellei s. If the ] rns velocity fluctuation is divided bv the avei age velocity iji the I est of the vessel, howevei the I atio is on the oi dei of 5 pei cent. This is also the level of I rns velocity fluctuation to the mean velocity in pipeline flow, Thei e ai e phenomena in rnici o-scale mixing that can occiu in mixing tanks that do not occiu in pipeline I eactoi s, Whethei this is good or bad depends upon the process requirements,... 

When dealing with water treatment applications you carmot avoid pipe flow calculations. We have a pipeline in which the throughput capacity of 500 Liter/sec. The flow is split into two pipelines and the inside diamter of the pipe is 350 mm. The length of the pipeline is 55 m. The entry loss is 0.70 and the exit loss is 1.00. There are two 45° bends and two 90° bends in the lines, (a) Determine the flow per pipe (b) determine the line velocity (c) determine the resulting hydraulic loss in meters. 

Heat transfer through a pipe wall. A pipeline parr 15m long carries water. Its internal diameter d, is 34 mm and its external diameter is 42 mm. The thermal conductivity of the pipe X is 40 W m K". The pipeline is located outdoors, where the outdoor temperature Oao is -8 C. Determine the minimum flow velocity necessary in the pipe to prevent the pipe from freezing. The heat transfer coefficient inside the pipe is = 1000 W m K and outside the pipe = 5 W m" K aiid = 4 W m -K . The specific heat ca-... 

The flows of gas and solid particles are assumed to be parallel. This means that the velocity of gas f and the velocity of solid particles c are both in the direction of the pipeline. On the other hand, because we do not assume a homogeneous flow at this stage of the theory, the absolute values of v and c may vary across the cross-section of the pipe. 

Equation (14.83) gives us an estimate for the velocity c at various pipeline angles 5 when the corresponding values for vertical and horizontal lines are known. It is an estimate, of course, because its derivation was based on the force balance of a single particle and not on the balance of the mixture of particles as a whole. 

FIGURE M.I2 The velocity difference for wood chips at various pipeline angles based on Eq. (14.83). 

Figure 2-48. Critical velocity characteristics depend on whether slurry is heterogeneous or homogeneous. By permission, Deramme-laere, R. H. and Wasp, E. J., Fluid Flow, Slurry Systems and Pipelines, Encyclopedia of Chemical Processing and Design, J. McKetta, Ed., M. Dekker, vol. 22,1985 [25].

Table 22.4 Pipeline capacities at specific velocities (metric SI units)...

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