Abstract

Moving packed bed heat exchangers (MPBHXs) are becoming an increasingly attractive option for particle-to-sCO2 heat exchangers (HXs) and integrating thermochemical energy storage based on metal oxide redox cycles with concentrated solar power (CSP) systems can provide significant advantages compared to sensible heat storage systems, such as higher energy storage density, higher working fluid (WF) temperature and potentially lower system costs. This work focuses on computational modeling of a shell-and-plate moving bed oxidation reactor-heat exchanger design that utilizes the exothermic oxidation of metal oxide particles under air flow to enhance thermal transport to sCO2 via both sensible and thermochemical heat exchange. A 2D volume-averaged continuum model is developed by coupling the counter-current air-particle flow, interphase heat transfer, thermochemical oxidation reaction, and species transport in the particle channel with sCO2 flow in the WF channel. The counter-flow particle-sCO2 sensible heat exchanger model is verified with previous numerical models in the literature, whereas the transport-reaction model within the particle channel is adopted from previous literature. For the baseline cases with similar geometry, operating parameters, and particle sizes, the total heat transfer for the TCES based HX was 16.71 kW compared to 4.62 kW for sensible only HX. The maximum extent of oxidation at the particle channel outlet was ∼75%, and the sCO2 outlet temperature was 692°C for reactive particles compared to 595°C for inert particles. A parametric study was also conducted to determine the effects of sCO2 and air flow rates on the temperature, extent of reaction, O2 absorption, and total heat transfer of the HXs.

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