Analytical and numerical investigation of heat and mass transport in catalytic microreactors

摘要: Microreactors for chemical synthesis and combustion have attracted increased attention in recent years. Due to the high degree of thermal control exhibited by microreactors, exothermic catalytic activity features heavily in these devices and thus advective-diffusive transport is of key importance in their analyses. An analytical study of the transport phenomena in a single microchannel microreactor filled with a porous medium is presented, first as a one-dimensional, then expanded to a two-dimensional model with catalytic activity. The systems under investigation include fluid and porous solid phases inside the microchannel under local thermal non-equilibrium (LTNE), in addition to the enclosing structure of thick walls subject to distinct thermal loads. The thermal diffusion of mass, viscous dissipation of the fluid flow is examined for both a heterogeneous catalyst placed on the channel wall and for a homogeneous reaction process. The axial and transverse variations of heat and mass transfer processes are considered to provide two-dimensional solutions of both the temperature and concentration fields. These are then used to calculate the local and total entropy generation within the system. A novel extension of an existing LTNE model capable of taking into account the enclosing structure as well as the porous solid and fluid phases is presented. The thickness of this enclosing structure is shown to have a major influence on heat and mass transport within the system, particularly the Nusselt number. Irreversibilities in the system are found to be dominated by the mass transfer contributions and the influence of the Soret effect as well as the …