Study on Preheating Techniques for Start-up of Tubular Solid Oxide Fuel Cells

For start-up of tubular solid oxide fuel cells preheating concepts of gas heating, induction heating, sequential hybrid of gas and induction heating and concurrent hybrid of gas and induction heating were experimented. Due to impossibility of heating-up of porous electric conductive layers in electromagnetic field, stainless steel material was adopted for the gas distributor tube, which is readily heated by induction method and transfers heat to adjacent layers. Start-up times of 95, 31, 49 and 20 seconds were attained for gas heating, induction heating, hybrid of sequential gas and inductive heating and hybrid of concurrent gas and induction heating methods respectively. Axial distribution of temperature in the course of start-up was steadier in hybrid methods which resulted in diminished axial temperature gradient and reduced performance degradation of the cell. A numerical model was developed and calibrated to predict the preheating phenomenon. Analytical results implied the positive effect of layers porosity on the heating rate, concerning mainly the gas heating methods.