Graded porosity artery for alkali metal thermal to electric conversion (AMTEC) cells

摘要

The present invention provides an alkali metal thermal to electric conversion (AMTEC) cell of the type employing an alkali metal flowing between a high-pressure zone and low-pressure zone in the cell through a solid electrolyte structure. The cell preferably includes a condenser communicating with the low-pressure zone for condensing alkali metal vapor migrating through the low-pressure zone from the solid electrolyte structure. An artery is coupled to the condenser for directing condensed alkali metal from the condenser toward a hot end of the cell. An evaporator for evaporating the condensed alkali metal is coupled to the artery channel and communicates with the high-pressure zone. The artery and evaporator combine to form a return channel which preferably includes a graded pore size capillary structure for creating a region having a large pore size transitioning in any predetermined manner to a region having a relatively smaller pore size. In this way, the capillary pressure provided by the return channel is optimized along its length while minimizing flow restrictions which are presented where the pore sizes are smaller than required to sustain alkali metal flow in portions of the return channel.