Concentrated solar power (CSP) is distinguished from other renewable energy sources by using thermal energy storage (TES) and conventional heat engines to dispatch energy on demand. However, in order to achieve a competitive levelized cost of energy (LCOE), CSP system costs must be reduced.
Recent studies of several triple periodic minimum surfaces (TPMS) and periodic nodal surfaces as heat exchangers have shown that Schwarz-D TPMS surfaces have excellent heat transfer properties. group IV-VI transition metal carbides, borides and composites are the most common ultra-high temperature ceramic (UHTC) materials. Prior to the introduction of additive manufacturing, TPMS devices were difficult to fabricate.
Compared to previous methods of manufacturing ceramic TPMS structures, adhesive jet additive manufacturing is developing as a promising and scalable method of forming ceramics. Adhesive jet printing has been used to fabricate UHTC heat exchanger plates in combination with reactive infiltration, but has not been used to fabricate UHTC TPMS structures sintered to high relative densities. Lessons learned from sintering nanomaterials suggest that low raw density during molding is not always an issue and that achieving good uniformity is more important.
In this study, the authors demonstrated the feasibility of adhesive spray additive manufacturing of UHTC-TPMS structures by sintering and printing empty candidates. Components with at least 92% theoretical relative density were created, which are also part of the TPMS.
The target density represents the transition from the intermediate to the final stage of sintering, which is necessary to sinter complex near-net forms to full density and suppress gas permeation using the sintering HIP technique. The purpose of the demonstration TPMS part was to see if the printing and sintering parameters obtained from the test specimens were applicable to the complex geometry that would be used for the heat exchanger design.
The team printed 9 cm 3 cubic TPMS pieces and sintered them without distorting or breaking them. Design topologies, materials and fabrication advances are presented to achieve best-in-class performance in molten chloride salts in CSP heat exchangers.
The researchers discuss the use of a combination of binder jet additive manufacturing and sintering to build ZrB2-MoSi2-based UHTC-TPMS cells. Because of its good processing characteristics and quality, ZrB2-MoSi2 was intentionally chosen as an invalid candidate to demonstrate the feasibility of a UHTC-TPMS heat exchanger until the best UHTC material for this application could be determined.
It was shown that adhesive spray additive manufacturing can be used to print and sinter UHTC-TPMS structures. In order to effectively limit distortion, it was found that a space-limiting strategy was needed. It was able to use conventional powder feedstock with a d50 of approximately 2-3 m, the same size used in conventional UHTC processing. These materials are sintered to a theoretical relative density of 92-98%, which is sufficient to prevent heat exchanger fluids from passing through the walls, separating the two regions and allowing for thermal isostatic pressure when higher densities are required.
