Session: 05-01 Thermochemical Energy Storage for CSP Applications

Paper Number: 107384

107384 - Numerical Investigation of Thermochemical Energy Extraction in a Moving Packed Bed Oxidation Reactor-Heat Exchanger 

Particle-based concentrated solar power (CSP) systems are essential to increase the working fluid (WF) temperature to enhance the thermal efficiency of the downstream power block with a sCO₂ or compressed air Brayton cycle. Moving packed bed heat exchangers are becoming an increasingly attractive option for particle-to-WF heat exchangers due to ease of operation and low operating costs. Integrating thermochemical energy storage (TCES) based on metal oxide redox cycles with CSP systems can provide significant advantages compared to sensible heat storage systems, such as higher energy storage density, higher working fluid 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 the WF via both sensible and thermochemical heat exchanger. 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 the turbulent gas flow in the WF channel (sCO₂ flow is considered at present). The counter-flow particle-sCO₂ sensible-only heat exchanger model is verified with previous numerical models in the literature, whereas the transport-reaction model within the particle channel is adopted from our previous model that was validated with a lab-scale moving-bed thermochemical reduction reactor. The coupled model is then implemented to study the parametric effects of heat exchanger design parameters and operating conditions, including particle sizes, particle-bed and sCO₂ channel geometries, particle and sCO₂ inlet temperatures, particle and sCO₂ mass flow rates, particle residence time, and particle to air mass flow rate ratio in the particle-bed channel, on the local particle-bed and sCO₂ temperature distributions, extent of oxidation of the particle bed, total heat transfer and heat exchanger effectiveness in comparison to sensible heat only particle-based heat exchangers. This work will provide a basis for demonstrating advantages of metal oxide-based TCES particle-WF heat exchangers compared to sensible heat only particle-WF exchangers.

Presenting Author: Ashreet Mishra Mississippi State University

Presenting Author Biography: Ashreet Mishra is a PhD student in the Mechanical Engineering Department at Mississippi State University working in the areas of modeling of solar receivers and reactors for solar thermal energy storage and utilization.