Compatibility of sodium and lithium in superalloy heat pipes. Final report, 1 January-31 December 1984

Heat pipes of superalloy materials are attractive for low-power terrestrial topping cycles and space power systems because of availability and relatively low cost. Six pipes of each material, stainless steel 304L and 310S, Hastalloy X and B, and Haynes 188 were tested. Eighteen pipes used sodium as a working fluid and were tested in an air environment to study both internal and external compatibility. The remaining twelve used lithium as a working fluid and were tested in a vacuum environment to study internal compatibility and external vaporization of material components. Some pipes had screen wicks and others had metal-fiber wicks. Test facilities and procedures are discussed in detail. Compatibility as well as performance of sodium pipes and lithium pipes is compared. As an aid in explaining the performance of the pipes, a simple theoretical analysis was made, and the results are discussed.