A computational analysis of the evaporator/artery of an alkali metal thermal to electric conversion (AMTEC) PX series cell

Abstract

The effect that the modeling of the wicking limitation of the capillary structure in the liquid return artery of an AMTEC PX-SB series cell has on cell performance was investigated. Preliminary evaluation of an AMTEC PX-SB computational model that predicts cell performance revealed that it did not take into account the effect that the maximum capillary pumping pressure rise has on performance. Starting with that model, enhancements were made to the program code to model the effect that the maximum flowrate limitation of the capillary structure has on predicted cell performance. It was found that for the AMTEC PX-SB series cell, inclusion of the limitation of the maximum flowrate of the capillary structure had no effect on performance predictions. Sodium flowrates required by the cell, at the tested conditions, were below the maximum capability of the capillary structure, therefore the limitation was not reached and so had no effect on the predicted performance of the cell. For hot-side cell temperatures from 1023 K to 1273 K, the required Socrates ranged from 1.73E-06 to 7.64E-06 kg/s, which were below the capillary structure's maximum wicking capability will be a limitation on AMTEC cell performance if the required flowrate of the cell exceeds the capillary structure's maximum flowrate. This enhanced model will be of benefit to AMTEC cell design variations that require sodium flowrates that exceed the maximum capability of their capillary structures at some operating conditions.