MAXIMUM CONVERSION EFFICIENCY OF THERMIONIC HEAT TO ELECTRICITY CONVERTERS USING MOLYBDENUM AS THE EMITTER

¹Abubakar Alkasim and ^2*Muhammad Tanko Baba

1 Department of PhysicsFederal; University of Technology, Yola;

2 Department of Mechanical Engineering; Federal Polytechnic, Mubi

E-mail: alkasimabbat @ yahoo.com and muhammadtanko@yahoo.com

ABSTRACT

An analysis of Thermionic converters of heat to electricity is made in terms of the potential difference between the top of the potential barrier in the inter electrode space and the Fermi level of the emitter, the potential drop across a load impedance connected in series to the converter, and the potential drop to the necessary electrical connection to the collector. This analysis is carried out by developing an expression with respect to the potential drops. The expression yields optimum values of load impedance, collector lead geometry and emitter work function in terms of collector voltage, emitter temperature, effective emmissivity of the emitter for both thetheoretical and practically obtain Richardson Dushman constant (usually denoted by A) for a Molybdenum metal surface. The expression developed is worked out numerically and the out come shows that (1) a low value of collector voltage is required for a high efficiency (2) a low radiation heat loss is required for a high conversion efficiency and (3) relatively low values of  emitter work function are required for maximum conversion efficiency at ordinary emitter temperature.

Key words: Thermionic converters, emitter, potential drop, Richardson Constant