Thermal and corrosion performance of cast cellular structures for heat storage applications

Latent thermal energy magazines based on phase change materials can utilize various heat transfer enhancers. Honeycomb castings were hereby proposed for this purpose. Cellular structures were manufactured by two combined technologies of 3D printing from polymer (poly-lactid acid, PLA) and subsequent investment casting with aluminum alloy (AC 44200). To take into account a possible degradation of metallic enhancers working in the environment of molten solar salt (KNO 3 and NaNO 3 in a weight ratio of 54:46), protective coatings were applied by plasma electrolytic oxidation (PEO). Coated and uncoated castings were subjected to an assessment of thermal performance during working cycles and corrosion resistance tests in molten nitrates under high-temperature conditions (260 °C) using electrochemical techniques. Cast aluminum structures, both coated and uncoated, successfully facilitate heat transfer by increasing the charging rate and maximum temperatures obtained in the PCM deposit. PEO layer does not seem to deteriorate heat transfer in relation to uncoated enhancer. In all of the tested arrangements, the corrosion process was suppressed as the immersion time in molten salts increased, but the best outcomes in terms of stability and corrosion protection in KNO 3 and NaNO 3 eutectic mixture were achieved for the as cast Al Si specimen. • Customized honeycomb castings significantly enhanced heat transfer in LTES units. • Protective PEO coatings can be an option to modify corrosion behavior in solar salts. • Thermal performance of composite PCM accumulators was increased by cellular castings. • Cast Al Si enhancers were found suitable to work in eutectic mixture of NaNO 3 and KNO 3 .