Session: 07-02: Fluidized Bed Heat Exchangers

Paper Number: 169991

169991 - Design Analysis of a Primary Particle Heat Exchanger With a Finned-Wall, Narrow-Channel Fluidized Bed 

Abstract: 

The development of an efficient high-temperature particle heat exchanger (HX) is crucial for advancing next-generation particle-based thermal energy systems for concentrating solar power (CSP). Fluidized bed heat exchangers offer an efficient solution for high-temperature thermal energy applications, including concentrated solar power (CSP). This study focuses on the design analysis with reduced order modeling of a primary particle-sCO₂ heat exchanger with narrow-channel fluidized beds using finned walls to enhance the bed-wall heat transfer coefficient.  High overall heat transfer coefficients U_HX are necessary to meet Gen3 CSP cost targets of $150 kW^-1_th  for particle-sCO₂ HXs (Albrecht and Ho, 2019). To-date, narrow-channel moving packed-bed HX (Albrecht et al., 2022) and smooth-walled fluidized bed HX have demonstrated U_HX  < 400 W m^-2 K^-1(Arthur-Arhin et al., 2024).  In this study, a reduced-order model, which uses experimentally derived correlations for fluidized bed-wall heat transfer and axial dispersion, is developed to identify pathways for achieving performance characterized by U_HX > 700 W m^-2 K^-1 to achieve Gen3 HX cost targets.

The finned-wall structures, made of Haynes 230 alloy, increase the HX effective surface area by a factor of over 3.5 and thereby enhance effective bed-wall heat transfer coefficients h_T,w,eff by as much as a factor of 2 relative to smooth walls.  The finned walls in the narrow-channel fluidized bed also reduce vertical particle dispersion that has been shown to reduce fluidized bed heat transfer (Arthur-Arhin et al., 2024) by restricting bubble growth as gas flows upward through the net-downward-flowing particle bed. The nominal 100-kW_th fluidized bed HX being developed by Brayton Energy employs bauxite CARBOBEAD particles in parallel narrow-channel fluidized beds approximately 1 m in height and bounded by walls confining Brayton's proprietary high-pressure flow channels for supporting high-pressure supercritical CO₂ (sCO₂).   Reduced-order HX modeling (ROM) similar to a previous reference for a smooth-wall fluidized bed HX (Arthur-Arhin et al., 2024), and the two-phase fluidized bed sub-model adopts mass, momentum, and energy conservation equations for the gas and solid phases (Brewster et al., 2025).  The ROM is used to analyze thermal performance, hydrodynamics, and energy transport across the system. The ROM enabled broad parametric analysis of how key design parameters such as bed and fin geometry, particle diameter and density, and solid and gas mass fluxes impact the HX thermal performance. Results from simulations using CARBOBEAD HSP 40/70 particles demonstrate that finned narrow-channel fluidized beds can achieve U_HX > 700 W m^-2 K^-1 with HX effectiveness over 70%.  Higher performance can be achieved with smaller particles.  The finned-wall fluidized bed HX design represents a promising pathway toward meeting Gen3 HX cost and performance targets and the ROM provides ana analysis tool for scaling up designs of narrow-channel, fluidized bed HX for next-generation CSP plants.

References

Albrecht, K., Laubscher, H., Bowen, C., Ho, C., 2022. Performance Evaluation of a Prototype Moving Packed-Bed Particle/sCO2 Heat Exchanger. https://doi.org/10.2172/1887943.

Albrecht, K.J., Ho, C.K., 2019. Design and operating considerations for a shell-and-plate, moving packed-bed, particle-to-sCO2 heat exchanger. Sol. Energy 178, 331–340. https://doi.org/10.1016/j.solener.2018.11.065.

Arthur-Arhin, W.J., Fosheim, J.R., Brewster, K.J., Madden, D.A., Albrecht, K.J., Jackson, G.S., 2024. Demonstration of a multi-channel fluidized bed particle-supercritical carbon dioxide heat exchanger for concentrating solar applications. Appl. Therm. Eng. 123242. https://doi.org/10.1016/j.applthermaleng.2024.123242.

Brewster, K.J., Martinek, J., Municchi, F., Arthur-Arhin, W.J., Fosheim, J.R., Ma, Z., Jackson, G.S., 2025. Reduced order modeling of a fluidized bed particle receiver for concentrating solar power with thermal energy storage. Sol. Energy 289, 113322. https://doi.org/10.1016/j.solener.2025.113322.

Turchi, C.S., Ma, Z., Neises, T.W., Wagner, M.J., 2013. Thermodynamic Study of Advanced Supercritical Carbon Dioxide Power Cycles for Concentrating Solar Power Systems. J. Sol. Energy Eng. 135, 041007. https://doi.org/10.1115/1.4024030.

Presenting Author: Ifeoluwa Ogunmola Colorado School of Mines

Presenting Author Biography: Ifeoluwa Ogunmola is a Ph.D. candidate in the Dept. of Mechanical Engineering at the Colorado School of Mines. She is working on high-temperature, particle-based thermal energy storage and capture in the group of Prof. Greg Jackson. Ife received her B.S. in Mechanical Engineering from the University of Maiduguri in Nigeria and an M.S. in Mechanical Engineering from the University of Debrecen in Hungary.