Experimental characterization of an additively manufactured heat exchanger for high temperature and pressure applications

High-performance heat exchangers are essential components in applications related to aerospace, industrial processes, and power generation. In power generation, the primary heat exchangers (HX) in future supercritical fluid Brayton cycles need to operate at temperatures in excess of 700 degrees C and pressures of 200 bar, necessitating the need for novel designs, high-temperature alloys, and new manufacturing methods to develop compact and high efficiency components. In this work, the design, fabrication, and experimental characterization of an additively manufactured (AM) primary HX for chloride molten salt (MS) to supercritical carbon dioxide (sCO2) is presented. The primary HX can also be used for extracting heat from a high temperature waste heat stream to sCO2. The primary HX is fabricated with Haynes 282 alloy via laser powder bed fusion AM. The core of the primary HX is comprised of a pin array on the sCO2 side and a three-dimensional periodic lattice network on the hot side. The sCO2 headers are aerodynamic in shape and are integrated within the MS flow path to permit scalability of the primary HX and permit a near counter-flow exchange of heat. A 20-pair primary HX is experimentally characterized using 200 bar sCO2 on the cold side and heated air as a surrogate for chloride MS on the hot side. Experimental results are used to validate a core thermofluidic model for the primary HX. The model predicts heat transfer rate and exit temperature of the air and sCO2 streams, on average, to within 1.72 %, 0.75 %, and 1.46 %, respectively. The validated model is used to estimate the volumetric and gravimetric power density of the MS-sCO2 heat exchanger, and the impact of varying inlet temperatures and flow rates of both streams on the primary HX performance. Considerations for AM fabrication and assembly of a modular 1 MW unit are provided.