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Drag factor

For these entrapped contaminant spheres, the diffusion is rapid, on the order of seconds rather than days. Kahn et al. (2000) suggested a diffusion model for xenobiotics with a slow desorption phase, with a half-life of years rather than seconds, assuming that diffusion is hindered by the natural organic matter matrix and occurs when the dimensions of diffusing molecules approach those of the pores. Under these conditions, hindrance from the wall becomes significant (Renkin 1954) and the drag factor F can be expressed as... [Pg.126]

There are three useful measures of the effect of bounding walls on drag. A drag factor can be defined, based on the same particle at the same fluid velocity ... [Pg.223]

Step 2. The drag factor C is to be determined next, using the following equation (Eq. 5-222 from Perry) ... [Pg.153]

The simplest case to consider is the settling of a single homogeneous sphere, under gravity, in a fluid of infinite extent. Many experiments have been carried out to determine the relationship between settling velocity and particle size under these conditions and a unique relationship between drag factor (C ) and Reynolds number Re) has been found that reduces to a simple equation, known as the Stokes equation, at low Reynolds number. [Pg.295]

The drag factor needs to be modified, for particles settling in a gas, to take account of the molecular nature of the gas. At low pressures, if the mean free path of the gas molecules (A) is much greater than the size of the... [Pg.309]

Drag factor, drag coefficient/ Stokes drag... [Pg.120]

Dillon SJ, Behtaa SK, Harmer MP (2008) An experimentally quantifiable solute drag factor. [Pg.577]

According to Eq. 6.11, the DMFC determination of the methanol permeability requires the knowledge of the methanol drag factor, because the electro-osmotic flux could afford for a considerable fraction of the methanol flow, particularly at high methanol concentrations. An important drawback of this method is that the methanol drag coefficient is not well known, so Ren et al. [299] assumed that it was similar to the water drag coefficient ( =2.5). However, some recent NMR [300] and electro-osmosis [301] studies would indicate that this assumption is not valid, leading to considerable uncertainties in the methanol permeability coefficients determined by this method. [Pg.146]

When the solute dimension is no longer orders of magnitude smaller than the pore dimensions, the solute molecules experience an additional transport resistance due to the proximity of the pore wall. The effective diffusion coefficient is reduced further by a hindrance factor/ drag factor Gm i i,rp). If the solute molecules are assumed spherical of radius r, and diffusing through the centerline of the pore of radius, tp, Faxen s expression may be used to estimate Gor for (r,rp) < 0.5 (Lane, 1950 Renkin, 1954) ... [Pg.100]


See other pages where Drag factor is mentioned: [Pg.173]    [Pg.126]    [Pg.230]    [Pg.362]    [Pg.340]    [Pg.288]    [Pg.277]    [Pg.52]    [Pg.359]    [Pg.386]    [Pg.323]    [Pg.106]    [Pg.125]    [Pg.249]    [Pg.260]    [Pg.422]    [Pg.11]    [Pg.455]    [Pg.909]   
See also in sourсe #XX -- [ Pg.223 ]




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