Session: 05-03: Concentrating Solar Power I: Receiver Applications

Paper Number: 138172

138172 - Performance of a Narrow-Channel Fluidized Bed With Extended Internal Surfaces for Indirect Particle Receivers 

Abstract: 

Next-generation (Gen-3) concentrating solar power (CSP) plants are being designed that employ solid oxide particles as both the receiver heat transfer fluid and low-cost thermal energy storage (TES) media at temperatures above 700 ^oC[1]. However, developing reliable high-temperature particle receivers remains a challenge because design requirements include particle outlet temperatures > 700 ^oC, thermal efficiencies above 85%, and scalability to at least 100 MW_e for commercial CSP deployment[2]. Current design efforts include falling particle curtains[3,4] , rotary kins[5], and indirect particle receivers[6]. Indirect receivers offer numerous operational advantages such as a wider variety of operable particles and no risk of particle spillage in high wind conditions. However, efforts such as this one are ongoing to identify receiver designs and operations that provide adequate particle-wall heat transfer to maintain confinement wall temperatures within wall material limits at relatively high incident solar flux. Recent efforts[7,8] have shown that mild bubbling fluidization in narrow channel flows can enable heat transfer coefficients above 1000 W m^-2 K^-1 which allows for effective solar fluxes up to 250 kW m^-2 while maintaining peak wall temperatures below 900 ^oC. 

Recent work initially intended for particle-sCO2 heat exchangers have shown further heat transfer enhancement suitable for receiver applications can be achieved through interior fins, with increased h_T,w by an additional 50% beyond a bubbling fluidized bed. Heat transfer coefficients above 1500 W m^-2 K^-1 have been measured at bed temperatures of 450 ^oC, with even higher values predicted at typical receiver operating temperatures. This work was done in our narrow channel test facility with a 12 mm bed depth, 100 mm width, and 250 mm height the main heat transfer section. This facility can simulate receiver-like conditions with near-IR lamps which can produce concentrated radiative fluxes up to 200 kW m^-2. Experiments of Geldart B particles up to 450 ^oC, excess dimensionless gas velocities, Û, up to 100, and particle flows up to 36 kg m^-2 s^-1 have been completed. Several oxide particle types being considered for TES were studied, including multiple sizes of CARBO aluminum oxide particles (304-408 µm), silica sand (225 µm), and olivine sand (159 µm). Current trends have been consistent with classical fin analysis and previous experiments, with additional particle flow dependencies. Previous efforts with flat walls indicated no mass flow dependencies on heat transfer[8], yet increases in h_T,w were observed with the finned plates. This indicates the smaller effective hydraulic diameter between the fins is more prone to channeling, and increased particle flow rates can aid with breaking up low pressure gas flow paths through the test section. Beyond heat transfer impacts, the extrusion of extended surfaces into the flow path also decreases vertical mixing in the channels, characterized by a 65% reduction the axial dispersion coefficient D_yy,s. Heat transfer and flow analysis of these efforts will be presented, along with analysis of its applicability in indirect particle receivers.

 

[1] Mehos M., et al., Concentrating solar power gen3 demonstration roadmap. NREL Technical Report. 2017

[2] Ho, C. A review of high-temperature particle receivers for concentrating solar power. Applied thermal engineering. 109. 958-969, (2016)

[3] Ho, C., et al., 2017. Journal of Solar Energy Engineering 139.

[4] Kim, J.S., et al., 2017. Design boundaries of large-scale falling particle receivers. AIP Conference Proceedings 1850, 030029.

[5] Miriam Ebert, et al., "Operational experience of a centrifugal particle receiver prototype", AIP Conference Proceedings 2126, 030018 (2019)

[6] Martinek, J and Ma, Z. Granular Flow and Heat-Transfer Study in a Near-Blackbody Enclosed Particle Receiver. Journal of Solar Energy Engineering. 5, 051008. (2015)

[7] Fosheim JR. et al, "Narrow-channel fluidized beds for particle-sCO2 heat exchangers in next generation CPS plants", AIP Conference Proceedings 2445, 160007 (2022)

[8] Brewster, K., et al., “Particle-wall heat transfer in narrow-channel bubbling fluidized beds for thermal energy storage”. Submitted to the International Journal of heat and mass transfer. (2024)

Presenting Author: Keaton Brewster Colorado School of Mines

Presenting Author Biography: Keaton Brewster is a Ph.D. candidate in Mechanical Engineering at the Colorado School of Mines. He has worked on several high temperature particle fluidized bed projects for CSP-TES, including an indirect fluidized bed particle receiver project led by the National Renewable Energy Laboratory, a finned particle-sCO2 fluidized bed heat exchanger project led by Brayton Energy, and a particle-sCO2 fluidized bed heat exchanger project led by the Colorado School of Mines and tested at Sandia National Labs.

Authors:

Keaton Brewster Colorado School of Mines
Fuqiong Lei Colorado School of Mines
Winfred Arthur-Arhin Colorado School of Mines
Jesse Fosheim Brayton Energy
Federico Municchi Colorado School of Mines
Gregory Jackson Colorado School of Mines