Linear velocity, average

The average linear velocity u of the mobile phase in terms of the column length L and the average linear velocity of eluent (which is measured by the transit time of a nonretained solute) is... 

A solute s capacity factor can be determined from a chromatogram by measuring the column s void time, f, and the solute s retention time, (see Figure 12.7). The mobile phase s average linear velocity, m, is equal to the length of the column, L, divided by the time required to elute a nonretained solute. 

By the same reasoning, the solute s average linear velocity, v, is... 

The solute can only move through the column when it is in the mobile phase. Its average linear velocity, therefore, is simply the product of the mobile phase s average linear velocity and the fraction of solute present in the mobile phase. 

In static runs gas is supplied to the ion source only at a rate sufficient to compensate the outflow through the leak (0.5 cc./sec. for air, equal to conductance of leak). The gas mixtures were prepared in two 2-liter storage flasks of the gas handling system. Flow runs can be made by passing gas through the ion source. Different flow rates were obtained by interposing capillary tubes in series with the flow system. Flow rates with an average linear velocity of up to 10 meters sec.-1 could be obtained. Since the distance from the foil window to the leak is about 3 cm., the contact time for irradiation at this velocity is some 3 msec. 

According to Scott the average linear velocity can be replaced by (4u,/[p 1]) in equation (1.35) to permit evaluation entirely in... 

Fig. 4.5.16 Schematic drawing of a boundary layer mixing mechanism. It is proposed that a thin layer with thickness 8 has a linear velocity profile with average velocity V/2. Material with bulk droplet volume fraction ( >in is drawn into the creamed layer (area Ac) and material with average creamed layer volume fraction (j)ou, is swept out. The remainder of the emulsion (inside the dashed circle) is stagnant.

The analysis can be made in situ using an optical, thermal, electrical or other method. The average time, during which the reaction proceeds before an element of volume and reaches a distance d along the reaction tube, is d/v, where v is the linear velocity. From the measurements made at various... 

In a cube of side X, the volume of free space is eX3 so that the mean cross-sectional area for flow is the free volume divided by the height, or eX2. The volume flowrate through this cube is ucX2, so that the average linear velocity through the pores, u, is given by ... 

FIGURE 13 van Deemter curve showing the relationship of HETP vs.average linear velocity.The van Deemter curve has a classical shape and is a composite plot of A, B and C terms (plotted below to show their contributions). This diagram is adapted from Reference 9. 

The narrow-bore column approach is a very effective and is the most popular way of increasing analysis speed. Substantial reductions in analysis times are achieved by exploiting two factors a shorter column length and the application of higher than optimum average linear velocities. Operating under optimum... 

The shear rate (s ) at the membrane surface is given by = 9ivld (cf. Example 2.2), where v is the average linear velocity (cm s ), d is the fiber inside diameter (cm), and Dp is the molecular diffusion coefficient (cm s ) all other symbols are as in Equation 8.4. Hence, Equation 8.6 is most likely applicable to UF in hollow-fiber membranes in general. 

When a culture medium flows in a circular tube as a laminar flow, determine the fraction of the medium that passes through the tube with a higher velocity than the averaged linear velocity. 

For a given solute show that the time of analysis - which can be compared with the retention time of the compound held longest on the column - depends, amongst other things, upon the length of the column, the average linear velocity of the mobile phase and upon the volumes Fs and VM which indicate respectively the volume of the stationary and mobile phases. 

Average linear velocities (cm/s) Change in viscosity with TfC)... 

Representing the average linear velocity by u, the kinetic equation for chromatography for capillary columns, as introduced by Golay, is written as ... 

Compressed into a 6-inch (ID = 5.761 inches) pipeline at 1000 psia is 2.4 MMscfd of the separator gas of page 9 of Table 10-1. Assume the temperature is 100°F. Calculate the actual volumetric flow rate in cubic feet per day, the mass flow rate in pounds per hour, and the superficial gas velocity (average linear velocity) in feet per second. Assume the heptanes plus fraction has the properties of n-heptane. 

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