Parasitic heat loss reduction in AMTEC cells by heat shield optimization

Abstract

Alkali metal thermal to electric conversion (AMTEC) cell performance can be increased by the proper design of thermal radiative shielding internal to the AMTEC cell. These heat shields essentially lower the radiative heat transfer between the heat input zone of the cell and the heat rejection zone of the cell. In addition to lowering the radiative heat transfer between the heat input and heat rejection surfaces of the cell, the shields raise the AMTEC cell performance by increasing the temperature of the beta'' alumina solid electrolyte (BASE). This increase in temperature of the BASE tube allows the evaporator temperature to be increased without sodium condensing within the BASE tubes. Experimental testing and theoretical analysis have been performed to compare the relative merits of two candidate heat shield packages: 1) chevron, and 2) cylindrical heat shields. These two heat shield packages were compared to each other and a baseline cell which had no heat shields installed. For the two heat shield packages, the reduction in total heat transfer is between 17% to 27% for the heat input surface temperature varying from 700/spl deg/C, 750/spl deg/C, and 800/spl deg/C with the heat rejection surface temperature kept at 300/spl deg/C.