Project Title:

Insoluble Coatings for Stirling-Engine, Heat-Pipe Condenser Surfaces

10.01-6551B
912235
Insoluble Coatings for Stirling-Engine, Heat-Pipe Condenser Surfaces
Thermacore, Inc.
780 Eden Road
Lancaster
PA
17601
Peter M.
Dussinger
717-569-6551
LeRC
NAS3-26324
205

10.01-6551B
912235

Abstract:

Insoluble Coatings for Stirling Engine, Heat-Pipe Condenser Surfaces
Dish Stirling systems are one of the most promising applications of the Stirling
engine technology. Solar energy is concentrated by a parabolic reflector and is directed
to a liquid-metal, heat-pipe receiver that delivers concentrated solar energy at
a uniform temperature to the Stirling engine. One issue raised in the design phase
of heat-pipe receivers was the solubility of the Stirling engine heater-head materials
in the liquid metal working fluid, typically sodium, potassium, or NaK. Phase I evaluates
candidate coating materials, applied to nickel heater-head materials, that are practically
insoluble in sodium, potassium, or NaK. Recent developments in coatings and coating
application technology, developed for wear and surface damage resistance in liquid-metal,
nuclear reactor systems, are also demonstrating corrosion resistance. The rate of
corrosion is two orders of magnitude less than nickel-based superalloys. The majority
of the solubility data in the literature was collected in pumped loop environments.
To establish the reliability of Stirling engine receivers and heater heads, a testing
program to determine corrosion rates in heat pipes operating at simulated Stirling
engine conditions with insoluble coatings will be developed.
This technology can be incorporated into terrestrial Stirling thermal power systems,
space Stirling power systems, and ultimately will be used for any long-life, high-reliability,
liquid-metal heat pipe applications.
Stirling engine, heat pipe, corrosion, solubility, solar thermal