Study of propane/air catalytic combustion in heat recirculating U-bend and spiral microcombustors

Combustion in catalytic microreactors has applications in portable power generation and process intensification. In this work, catalytic microcombustion of propane in two geometries – U-bend and Spiral, which have heat recirculation in counter-current and co-current configurations respectively – is investigated computationally. 2D CFD simulations are performed to analyze the performance characteristics of both the reactors and a comparative study is presented. Heat recirculation due to transverse heat transfer occurs in both the geometries. U-bend reactor is more stable than spiral over a wider range of operating conditions due to effective counter-current heat exchange. Spiral reactor has higher peak temperatures due to better internal heat recirculation and lower heat loss to the ambient. Excess enthalpy combustion in both the reactors allows combustion at lean conditions, resulting in lower temperatures and fairly uniform temperature profile, useful for coupling thermoelectrics.