Mixture velocity

Figure 6-32, taken from Govier and Aziz, schematically indicates four flow pattern regions superimposed on a plot of pressure gradient vs. mixture velocity = Vl -t- V5 = Qj + ( s)/A where and Vs are the superficial liquid and solid velocities, Qi, and ( 5 are liquid and solid volumetric flow rates, and A is the pipe cross-sectional area. is the transition velocity above which a bed exists in the bottom of the pipe, part of which is stationary and part of which moves by saltation, with the upper particles tumbling and bouncing over one another, often with Formation of dunes. With a broad particle-size distribution, the finer particles may be fully suspended. Near V 4, the pressure gra-... 

FIG. 27-33 Inspirator (gas-jet) mixer feeding a large port premix nozzle of the flame retention type. High-velocity gas emerging from the spud entrains and mixes with air induced in proportion to the gas flow. The mixture velocity is reduced and pressure is recovered in the ventnii section. (F om North Ameiioan Comhnstion Handbook, 3d ed., Notih American Manufacturing Company Cleveland 1996. )... 

The properties of natural gas are dominated by those of methane, notably a low maximum flame speed of 0.33 m/s. This strongly influences burner design, which must ensure that the mixture velocity is sufficiently low to prevent blow-off. Light-back , on the contrary, is very unlikely with such a low flame speed. 

If air is injected so that the mixture velocity is increased to buL, then the total length of liquid slugs in the pipe will be (1 /b)l. Then, neglecting the pressure drop across the air slugs, the two-phase pressure drop — APTp will be given by ... 

Figure 5.6. Drag ralio as function of mixture velocity...

In a recent study of the transport of coarse solids in a horizontal pipeline of 38 mrrt diameter, pressure drop, as a function not only of mixture velocity (determined by an electromagnetic flowmeter) but also of in-line concentration of solids and liquid velocity. The solids concentration was determined using a y-ray absorption technique, which depends on the difference in the attenuation of y-rays by solid and liquid. The liquid velocity was determined by a sail injection method,1"1 in which a pulse of salt solution was injected into the flowing mixture, and the time taken for the pulse to travel between two electrode pairs a fixed distance apart was measured, It was then possible, using equation 5.17, to calculate the relative velocity of the liquid to the solids. This relative velocity was found to increase with particle size and to be of the same order as the terminal falling velocity of the particles in the liquid. 

In the absence of a direct measurement of the in-line concentration of solids ey. it is necessary to make an estimate of its value in order that the hydrostatic pressure gradient in the pipe may be calculated. This can be done for a given mixture velocity u and delivered concentration C, provided that the velocity of the particles relative to the liquid UR is known. 

For suspensions of coarse particles The value calculated for the carrier fluid flowing alone at the mixture velocity is used. 

For a single-phase turbulent flow the ratio of the maximum to the average flow velocity is approximately 1.2, and the value of Co may also be close to 1.2 for a bubbly flow. Zuber and Findlay (1965) pointed out that, as the mixture velocity increases, the value of the exponent increases and flatter profiles result. 

As was shown before, the Leidenfrost temperature is the second transformation of heat transfer mechanisms. Empirical correlations have been established by film boiling data obtained from water at high pressure levels. For a wide range of steam-water mixture velocities, the correlation for hFB reported by Bishop et al. (1965), as shown in Eq. (4-37), is recommended for use in design. 

To consider the control volume form of the conservation of mass for a species in a reacting mixture volume, we apply Equation (2.14) for the system and make the conversion from Equation (3.12). Here we select/ = pt, the species density. In applying Equation (3.13), v must be the velocity of the species. However, in a mixture, species can move by the process of diffusion even though the bulk of the mixture might be at rest. This requires a more careful distinction between the velocity of the bulk mixture and its individual components. Indeed, the velocity v given in Equation (3.13) is for the bulk mixture. Diffusion velocities, Vi, are defined as relative to this bulk mixture velocity v. Then, the absolute velocity of species i is given as... 

Bunsen burner the conical flame angle (2) and the mean unburned mixture velocity (vu) in the tube can approximately give 5U ... 

In eq 51, the first term represents a convection term, and the second comes from a mass flux of water that can be broken down as flow due to capillary phenomena and flow due to interfacial drag between the phases. The velocity of the mixture is basically determined from Darcy s law using the properties of the mixture. The appearance of the mixture velocity is a big difference between this approach and the others, and it could be a reason the permeability is higher for simulations based on the multiphase mixture model. 

The wave travels at some definite velocity (burning vel) against the unbumed mixture. Velocity depends on ihe composition of the mixture being zero at the limits and at a max at some intermediate composition (eg 9.5% for firedamp). There are three types of flame ... 

It is noted from Eq. (7.78) that the maximum droplet holdup can be reached when the upward gas-solid mixture velocity Up approaches the sedimentation velocity of the droplets, assuming that no coalescence of droplets occurs. Under this condition, the collection efficiency is maximum. 

Other ideal Gas Properties Mixture Velocities and Effusion... 

Assuming the background gas species (i.e., the gas species which is not fuel, oxidizer, or product) is stagnant and that the reaction is confined to a thin reaction zone, the total mass-averaged gas mixture velocity,... 

TABLE 2 Detonation Mixtures" Velocities of Stoichiometric Hydrogen-Oxygen... 

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