Mobile phase velocity superficial

U Average mobile-phase velocity, = (superficial velocity)/s m/s LT-1... 

Mobile phase velocity. Chromatographers define the cross-section average velocity of the mobile phase as the ratio, u = L/fo, of the column length and the hold-up time or retention of a nonretained compoimd. This time should be corrected for the transit time through the extracolumn volumes between injection valve and column inlet and between column inlet and detector. Chemical engineers tend to prefer the superficial velocity, or ratio of the flow rate and the column cross-section area, wq = Fv/S. Obviously, we have ... 

Velocity There are three different definitions of the mobile phase velocity, the chromatographic, the interfacial, and the superficial velocity They are all defined as the ratio of the mobile phase flow rate to an estimate of the column volume and differ by the estimate of the column volume used. The chromatographic velocity uses the total volume in the column that is available to the mobile phase the superficial velocity, the geometrical column tube volume and the intersticial velocity the external or extra-particle volume. See Chapter 2, Section 2.3.3. 

Here uR is the velocity at which the solute band moves along the column and u is the velocity of the mobile phase that is, u = (superficial velocity)/e, where superficial velocity is volumetric flow rate divided by cross-sectional area of column and s is the fractional volume of column occupied by mobile phase. Most column packings are porous, in which case s includes both interstitial and pore (intraparticle) voidage, as defined in the note to Table 19.1, and here u is less than the interstitial velocity. 

As is the case for reactors with two or more mobile phases, a variety of flow regimes exist depending primarily on the gas superficial velocity (the driver for bubble column hydrodynamics) and column diameter. A qualitative flow regime map is shown in Fig. 19-38. 

Uq is the superficial velocity of the mobile phase, p is the density of the particles. 

In these equations, Mq is the superficial velocity of the mobile phase, e the interparticle void fraction, p and pp the porosity and the density of the packing material, respectively, K the adsorption equilibrium constant, Di the axial dispersion coefficient, Rp the particle radius, kf the external mass transfer coefficient, and Dg the... 

Superficial velocity The ratio of the mobile phase flow rate to the external or extra-particle column volume. See Chapter 2, Section 2.3.3. 

Here Z), is the axial molecular diffusion coefficient of the component i in the mobile phase and w denotes the mean superficial velocity in flow or z -direction. If the mean velocity w is veiy small, the axial dispersion coefficient is proportional to the diffusion coefficient. In the case w [Pg.547]

The first moments of the two components of propranolol hydrochloride were plotted against the inverse superficial velocity of mobile phase in Figure 4. Straight lines were fitted to the experimental points. According to Equation 4, the equilibrium constants were determined from the slopes of the hnes, which were found to be 4.36 and 6.31 for (S)-propranolol hydrochloride and f/ j-propranolol hydrochloride, respectively. 

Figure 4. Retention time of propranolol hydrochloride versus inverse superficial velocity of mobile phase...

To model the measured transient foam displacements, equations 2 through 12 are rewritten in standard implicit-pressure, explicit-saturation (IMPES) finite difference form, with upstream weighting of the phase mobilities following standard reservoir simulation practice (10). Iteration of the nonlinear algebraic equations is by Newton s method. The three primitive unknowns are pressure, gas-phase saturation, and bubble density. Four boundary conditions are necessary because the differential mass balances are second order in pressure and first order in saturation and bubble concentration. The outlet pressure and the inlet superficial velocities of gas and liquid are fixed. No foam is injected, so Qh is set to zero in equation... 

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