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shown to be small, and their effect upon transients is imperceptible 1n the cases treated.-ivThese studies show that mathematical models which adequately simulate chemical reactors in unsteady state must incorporate the following phenomena: the thermal capacity of the packing, finite (as distinguished from infinite) rates of heat transfer between fluid and packing, and coupling between concentration and temperature, Both of the one-dimensional models studied include these phenomena and yet are simple enough to be useful in further studies of reactor dynamics and in studies of reactor control.

Experimental observations of a reactor's frequency response when compared with mathematical models of the reactor revealed the need for accurate modeling of heat generation, heat exchange, and heat storage processes. The experiments were performed in a laboratory reactor with the exothermic reaction between hydrogen and oxygen catalyzed by platinum on granules of silica gel. This system permitted observation of several nonlinear effects.One‐ and two‐dimensional, locally linear, plug‐flow models of the continuum type were used for the comparison. One of the models included the effects of intraparticle diffusion of reactants. However, models that neglected intraparticle dynamic effects were found suitable here because the decay time for the diffusion process within the catalyst was short compared to the reactor's major thermal time constant. A two‐dimensional model was found to give an excellent representation of the very complex movement of concentration and temperature waves in this type of reactor, while a one‐dimensional model was found to serve well when radial gradients are small.

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