Packed beds microscopic models

In industrial reactors there are normally gradients in the species mass concentrations, temperature, pressure and velocity in all space directions. The fundamental microscopic equations give a detailed description of all the known mechanisms involved. In the chemical reactor engineering approach we desire to eliminate the mechanisms that is not essential for the reactor performance from the equations to reduce the computational demand. An appropriate engineering packed bed reactor model is thus tailored for its main purpose. It is as simple as possible, but still include a sufficient representation of essential mechanisms involved. 

We have already dealt with stationary phase processes and have noted that they can be treated with some success by either macroscopic (bulk transport) or microscopic (molecular-statistical) models. For the mobile phase, the molecular-statistical model has little competition from bulk transport theory. This is because of the difficulty in formulating mass transport in complex pore space with erratic flow. (One treatment based on bulk transport has been developed but not yet worked out in detail for realistic models of packed beds [11,12].) Recent progress in this area has been summarized by Weber and Carr [13]. 

ETC is an important parameter describing the thermal behavior of packed beds with a stagnant or dynamic fluid and has been extensively investigated experimentally and theoretically in the past. Various mathematical models, including continumn models and microscopic models, have been proposed to help solve this problem, but they are often limited by the homogeneity assumption in a continuum model (Wakao and Kaguei, 1982 Zehner and Schliinder, 1970) or the simple assumptions in a microscopic model... 

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