Standing and Propagating Temperature Waves on Electrically Heated Catalytic Surfaces

Reaction rates are often measured using a catalytic wire or ribbon, the resistance (average temperature) of which is kept at a preset value via electrical heating. Previous investigators assumed that the wire temperature was uniform. An IR-thermal imager shows that some temperature profiles have the shape of a stationary standing wave. A bifurcation map describes the organization of the regions with these standing wave temperature profiles. In some cases, the high temperature wave moves back and forth on the ribbon, with continuous changes in its shape. This leads to both oscillatory and chaotic changes in the overall rate of heat generated by the reaction. The dynamic behavior of the overall reaction rate is different and less regular than that of local temperatures on the ribbon. The power spectrum of the overall rate of heat generation decays exponentially, while that of the local temperatures decays as a power law. Ignoring the nonuniform nature of the temperature of the ribbon may lead to severe pitfalls in the determination of the kinetic rate expression and/or its parameters