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COMPUTATIONAL FLUID DYNAMICS SIMULATION OF THE THERMAL UNIFORMITY IN CATALYTIC MICRO-COMBUSTORS

Junjie Chen, Wenya Song, Deguang Xu
Frontiers in Heat and Mass Transfer (FHMT) 8 - 21 (2017)


Abstract


The combustion and heat transfer characteristics of hydrogen-air or methane-air mixtures in catalytic micro-combustors were studied numerically to assess the impact of wall thermal properties and key operation parameters on the thermal uniformity. A two-dimensional computational fluid dynamics (CFD) model was developed with detailed hetero-/homogeneous chemistry, heat conduction within the solid wall, surface radiation heat transfer, and external heat losses. Parametric studies were carried out to investigate the effect of wall thermal conductivity, feed composition, and flow rate on the thermal uniformity during highly exothermic catalytic reactions. Comparisons of hydrogen- with methane-air systems were made. Based on these insights, an overall energy balance analysis was performed in terms of enthalpy loss. It was shown that the wall thermal properties strongly affect the thermal uniformity, but little impact on the extinction limit and conversion. The feed composition and flow rate have a significant impact on the operating temperature, but only a moderate effect on the thermal uniformity. Most of the enthalpy released by the exothermic reaction is lost to the surroundings under certain conditions, although this energy exchange becomes less efficient as the flow rate increases. This feature is beneficial for heat-exchanger applications.

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DOI: http://dx.doi.org/10.5098/hmt.8.21

ISSN: 2151-8629