| The AMTEC (Alkali Metal Thermal to Electric Converter) cell power system is a promising technology for the space and terrestrial applications. With no moving parts, it only needs a heat source to vaporize liquid sodium. Electrons are stripped from the sodium vapor passing through a Beta Alumina (coated electrolyte) tube to generate electrical power. The AMTEC cell power is limited by the cell hot and cold end temperatures, but higher hot end temperature challenges the material strength. Another major limitation is Capillary Artery eVaporator (CAV) reliability determined chiefly by the thermodynamic limits where phase change can occur inside the porous structure. An optimized capillary artery evaporator design is proposed to improve the CAV performance and allow the AMTEC cell to pass the accelerated life tests for the space power applications.; We investigate the limits on the CAV device and simplify its performance by evaluating an inverse heat conduction problem using conformal mapping. Analytical expressions are derived for a uniform heat flux evaporation surface shape predicted to improve the CAV performance. Some limitations of the conformal mapping method are avoided by using an Indirect Desingularized Boundary Integral method to solve for CAV performance. A model based on this method has been developed and validated with existing test data. Based on the validated model, we propose an objective function including reliability, efficiency and power density to evaluate CAV performance. Varying different artery and evaporator lengths, pore sizes, evaporation surface shapes, cell lengths, and a cell hot end temperature gives an optimized design, improving the current CAV performance by 14%. |
