Design and operating considerations for a shell-and-plate, moving packed-bed, particle-to-sCO2 heat exchanger

Abstract

An efficient modeling methodology for simulating moving packed-bed heat exchangers for the application of particle-to-sCO2 heat transfer in next-generation concentrating solar power (CSP) plants is presented. Moving packed-bed heat exchangers have application to power-cycle heat addition for particle-based CSP plants and indirect energy storage for direct sCO2 CSP receivers. Further development of moving packed-bed heat exchangers for application to commercial CSP systems requires numerical simulation tools for the design and evaluation of particle-to-sCO2 heat transfer. In this paper, a steady-state reduced-order model of a shell-and-plate moving packed-bed heat exchanger is presented and used to investigate design considerations and performance limitations. The model appropriately captures the flow configuration of a multi-bank shell-and-plate design where the local cross-flow and global counter-flow configurations are addressed. This allows for the design tradeoffs in heat exchanger geometry and particle properties to be explored on the heat exchanger conductance and sCO2 pressure drop. Overall heat transfer coefficients for the particle-to-sCO2 heat exchanger at CSP operating temperature (500–800 °C) can approach 400 W m−2 K−1 using particle channel dimensions of 4 mm with particle diameters of 200 µm. The sensitivity of particle thermophysical properties was also explored to identify important parameters for improving the overall heat transfer coefficient that can be leveraged in the development of alternative particles. Packed bed void fraction and solid thermal conductivity were identified to be areas for potential improvement of sintered bauxite particles, which could increase the overall heat transfer coefficient by up to 60 W m−2 K−1. To achieve DOE cost targets (<$150 kWt−1) for sCO2 power cycle heat addition, diffusion bonded plates containing sCO2 microchannels must be produced at less than $2400 m−2 for the moving packed-bed heat exchanger to become commercially viable.