Eddy dispersion coefficient

The eddy dispersion coefficient has been measured and correlated empirically as... 

Axial and radial dispersion or non-ideal flow in tubular reactors is usually characterised by analogy to molecular diffusion, in which the molecular diffusivity is replaced by eddy dispersion coefficients, characterising both radial and longitudinal dispersion effects. In this text, however, the discussion will be limited to that of tubular reactors with axial dispersion only. Otherwise the model equations become too complicated and beyond the capability of a simple digital simulation language. 

In the above case, D is an eddy dispersion coefficient and Z is the axial distance along the reactor length. When combined with an axial convective flow contribution, and considering D as constant, the equation takes the form... 

Here the nomenclature is the same as in Sec. 4.4.2 and in addition, Dq is the effective eddy dispersion coefficient for the organic or extract phase (m / s) and Dl is the effective eddy dispersion coefficient for the aqueous or feed phase (m / s). The above equations are difficult to solve analytically (Lo et al., 1983) but are solved with ease, using digital simulation. 

Eddy dispersion coefficient Inverse residence time Inverse dispersion time Fractional phase holdup Superficial phase velocity... 

Bubble columns are used for liquid aeration and gas-liquid reactions. Thus, finely suspended bubbles produce large interfacial areas for effective mass transfer, where the contact area per unit volume of emulsion is calculated from the expression a 6e/dg, where e is the volume fraction of injected gas. While simple to design and construct, bubble columns sustain rather large eddy dispersion coefficients, and this must be accounted for in the modeling process. For cocurrent operation, liquid of... 

A final value needed to solve the complete set of equations is the eddy dispersion coefficient, Eq. The Chung and Wen (1968) correlation is commonly used to determine Eq. 

---