Evaluation of Alternative Designs for a High Temperature Particle-to-sCO₂ Heat Exchanger

This paper presents an evaluation of alternative particle heat-exchanger designs, including moving packed-bed and fluidized-bed designs, for high-temperature heating of a solar-driven supercritical CO₂ (sCO₂) Brayton power cycle. The design requirements for high pressure (≥20 MPa) and high temperature (≥700 °C) operation associated with sCO₂ posed several challenges requiring high-strength materials for piping and/or diffusion bonding for plates. Designs from several vendors for a 100 kW-thermal particle-to-sCO₂ heat exchanger were evaluated as part of this project. Cost, heat-transfer coefficient, structural reliability, manufacturability, parasitics and heat losses, scalability, compatibility, erosion and corrosion, transient operation, and inspection ease were considered in the evaluation. An analytic hierarchy process was used to weight and compare the criteria for the different design options. The fluidized-bed design fared the best on heat transfer coefficient, structural reliability, scalability, and inspection ease, while the moving packed-bed designs fared the best on cost, parasitics and heat losses, manufacturability, compatibility, erosion and corrosion, and transient operation. A 100 kW_t shell-and-plate design was ultimately selected for construction and integration with Sandia's falling particle receiver system.