Incipient dryout in the evaporator of vapor anode, multi-tube alkali-metal thermal-to-electric conversion cells

Incipient dryout in the evaporator wick of a 5-tube PX-3A type stainless steel AMTEC cell and an 8-tube, Nb-1Zr/C-103 AMTEC cell is investigated using a 2-dimensional thermal-hydraulic model of the evaporator wick and the liquid sodium return artery. Results showed that incipient dryout in the evaporator wick occurs when either the hot side temperature exceeds, or the cell electrical current (or sodium flow rate) drops below a cut-off value. The operation domains in which these cells are capillary limited are developed and compared.