Thermal modelling of a porous silicon-based pellistor-type catalytic flammable gas sensor with two supporting beams

A three-dimensional transient thermal mathematical model of a porous silico n based pellistor with two supporting beams was developed. The model was nu merically solved using the implicit alternating-direction finite difference method. A computer program written in ANSI C and run on a VAX/VMS computer was utilised to study the influence of the power consumption and the main geometrical dimensions (membrane, beam and heater size) of the pellistor me ntioned above on its transient and steady-state thermal behaviour. It was f ound that considerable improvement in the thermal behaviour of the pellisto r could be achieved by reducing the membrane size (length and width). The o ptimal beam length was determined as 100 mu m. By comparing the main source s of energy dissipation it was found that energy was lost predominantly thr ough the heat conduction into the supporting beams. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.