The Wall Heat Transfer Phenomenon of Premixed CH4/Air Catalytic Combustion in a Pt Coated Microtube

In this paper, a 2D model with detailed heterogeneous chemical mechanism has been employed to investigate the heat transfer phenomenon of premixed CH4/air catalytic combustion in a Pt coated microtube. Especially, the thermal processes such as coupled heat transfer between the internal surface of the microtube and the gas phase, thermal conduction along the solid structure, convection and radiation between the external surface and the environment are comprised in the simulation. The results show that the thermal conductivity of different solid wall materials dramatically affects the uniformity of temperature distribution of the catalytic surface. To maintain stable combustion in the microtube, the thermal conductivity should exceed 0.49 W/m/K at least and conductive walls (FeCr alloy and corundum ceramic) are more appropriate to manufacture microcombustors. The extremely small Biot number at the external surface indicates that convective heat transfer coefficient and emissivity to the environment are the key factors determining the heat loss of the microtube. The amount of heat loss influences the reaction rate and residence time of the mixtures in the microtube, which would affect the conversion of CH4. An increase of the wall thickness improves the heat transfer along the solid structure, also increases the total heat loss.