Hatta number, significance

Additional experiments in a loop reactor where a significant mass transport limitation was observed allowed us to investigate the interplay between hydrodynamics and mass transport rates as a function of mixer geometry, the ratio of the volume hold-up of the phases and the flow rate of the catalyst phase. From further kinetic studies on the influence of substrate and catalyst concentrations on the overall reaction rate, the Hatta number was estimated to be 0.3-3, based on film theory. 

Equation 7.146 for the utilization factor corresponds to 7.107 for the case of heterogeneous catalysis with diffusional limitations. The analogy between 7.146 and 7.107 is complete when Shm = 1, i.e. when the reaction occurs simultaneously with diffusion throughout the complete liquid volume. The presence of a Sherwood number, besides the Hatta number, is needed to describe situations where a significant part of the reaction occurs in the bulk of the liquid, i.e. in series with the transport through the film. Such a situation is often encountered. Typical values for the Sherwood number are ... 

Conclusions Film Conversion Parameter Significance of the Hatta Number... 

Mass transfer and kinetics are both taken into consideration in the Hatta number. In a reactor designed for a particular reaction with a rate constant /cm , the value of Ha is a significant indicator of whether a large specific interfacial area or a large liquid holdup is needed. Conversely, in a given designed reactor, it indicates the extent to which reaction kinetics on the one hand, or the mass-transfer coefficient and the interfacial area on the other, will control the overall rate. These questions are fully explored in Section III. 

However, in contrast to regime A, the homogeneous reaction is significantly rapid as compared to the diffusion process in the film (Cg Bg k a). This ensures almost complete consumption of the amount of A supplied to the bulk liquid phase. Effectively, this implies Ag 0. In terms of Hatta number ... 

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