Double phase coaxial gas heater for molten carbonate fuel cell

An original small size, modular molten carbonate fuel cell (MCFC) has been patented (patent n°: PG 2003 A 0019) by researchers of the University of Perugia. The proposed MCFC may be conveniently employed for μCHP residential applications because of: - high efficiency; - long life; - natural gas supplying. Because of the small size and compact geometry of the proposed MCFC stack, a particular system for natural gas and water introduction is required: natural gas must be heated (stack temperature is 650°C) and mixed with steam in order to attain anodic humidification which is very important to improve MCFC working life. In this work, a double fluid (water, natural gas), phase transition heat exchanger which is suitable to stack geometrical constraints is proposed and studied; it is composed by two coaxial pipes. Two different solutions have been analyzed with different steam and fuel gas arrangements. By formulating and solving an original equations system, the geometrical configuration that minimizes the exchanger dimension has been identified.