The assumption of local thermal equilibrium (LTE) is very common in the study of reacting flows in porous media. The assumption simplifies the structure of the solutions and places fewer constraints on computational methods for the domain and boundary conditions. However, in certain systems, such as gas/solid metal hydride reactors, the boundary conditions may impose high energy transfer rates which produce slowly evolving phase change fronts coupled with rapid kinetics. Overall performance of the systems is proportional to the release or absorption of hydrogen, and this is sensitively related to temperature. Thus, capturing local departures from LTE is required. This paper directly evaluates the influence of these effects by solving an NLTE (non-local thermal equilibrium) formulation for coupled reactors as a function of the interphase heat transfer coefficient, hsf. The reactor dynamics and overall energy balances are compared to solutions previously obtained from LTE calculations. The results appear to be the first NLTE results for coupled reactors. They confirm the existence of NLTE effects and suggest the magnitude of hsf for which they can be minimized.

Issue Section:
Porous Media, Particles, and Droplets
Keywords:
chemical reactions, chemical technology, thermodynamic properties, chemically reactive flow, heat transfer, flow through porous media, Heat Transfer, Phase Change, Porous Media, Sorption Heat Pump, Two-Phase Flow
Topics:
Boundary-value problems, Flow (Dynamics), Heat, Heat pumps, Heat transfer, Hydrogen, Metals, Porous materials, Temperature, Thermal equilibrium, Absorption, Dynamics (Mechanics), Fluids, Decision analysis, Heat transfer coefficients
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