Coupled thermal, electrical, and fluid flow analyses of AMTEC converters, with illustrative application to OSC's cell design

Abstract

This paper presents the background and introduction to the OSC AMTEC (alkali metal thermal-to-electrical conversion) studies, which were conducted for the Department of Energy (DOE) and NASA's Jet Propulsion Laboratory (JPL). After describing the basic principle of AMTEC, the paper describes and explains the operation of multi-tube vapor/vapor cells, which have been under development by AMPS (Advance Modular Power Systems, Inc.) for the Air Force Phillips Laboratory (AFPL) and JPL for possible application to the Europa Orbiter, Pluto Express, and other space missions. It then describes a novel OSC-generated methodology for analyzing the performance of such cells. This methodology consists of an iterative procedure for the coupled solution of the interdependent thermal, electrical, and fluid flow differential and integral equations governing the performance of AMTEC cells and generators, taking proper account of the nonlinear axial variations of temperature, pressure, open-circuit voltage, inter-electrode voltages, current density, axial current, sodium mass flow rate, and power density. The paper illustrates that analytical procedure by applying it to OSC's latest cell design and by presenting detailed analytical results for that design. The OSC-developed analytic methodology constitutes a unique and powerful tool for accurate parametric analyses and design optimizations of the multitube AMTEC cells and of radioisotope power systems.