Liquid interstitial dispersion coefficient

Here, PeL = LJLdp/EZL, Reu = dppLUL/pLi GaL = dlgpl/pl, UL is the interstitial liquid velocity, and EZL is the liquid-phase axial dispersion coefficient. Furzer and Michell28 correlated the Peclet number to the dynamic holdup by a relation... 

The equation is written in terms of concentration and therefore is suitable for a liquid feedstock. By use of an appropriate equation of state, equation 6.19 is readily adapted for a gas feed. The loading on the adsorbent q is expressed in units of mass/mass. The first term represents axial dispersion within the bed the axial dispersion coefficient is Dj The second term represents convective flow within the bed the interstitial velocity is u (and is equal to the superficial velocity divided by the bed voidage). The third term represents the accumulation of adsorbate in the fluid phase while the fourth term represents the rate of adsorption which may be a function of both the fluid phase concentration and the loading on the adsorbent. In general ... 

At any level in the transition region, there will be a balance between the mixing effects attributable to (a) axial dispersion and to (b) the segregating effect which will depend on the difference between the interstitial velocity of the liquid and that interstitial velocity which would be required to produce a bed of the same voidage for particles of that size on their own. On this basis a model may be set up to give the vertical concentration profile of each component in terms of the axial mixing coefficients for the large and the small particles. 

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