Anisothermal gas–particle flow simulations for concentrated solar applications

Concentrated solar power (CSP) is a technology designed to harness the sun’s energy. In contrast with photovoltaics (PV), CSP plants use a different approach to generate electricity. CSP plants work by concentrating sunlight into a focalized beam aimed at a receiver. The high-temperature receiver then transfers its thermal energy to a working fluid, operating in a thermodynamic cycle for electric power generation. Compared to PV, CSP systems are capable of offering a more reliable supply of electricity when coupled with thermal energy storage (TES), thus offsetting one of PV’s major challenges. Currently used 1st and 2nd generation CSP plants typically use oil, steam, or molten salt as the working fluid. Their cycle efficiencies lie in the 28–44 % range, with peak temperature typically not exceeding 550∘^{\circ}C to prevent chemical degradation. 3rd generation CSP (under research) aims at greater than 50 % efficiency by increasing peak temperatures to at least 720∘^{\circ}C. This would be made possible by using new types of fluids, such as gas–particle fluidized beds. To make use of gas–particle beds, receiver wall-to-bed heat transfer needs to be studied and characterized. For such flows, numerical modeling is a powerful tool providing full access to the flow’s data under various operating conditions, without disrupting it. Particle-Resolved Numerical Simulation is the most accurate numerical modeling technique, capturing the full range of scales in the flow. In our research, Particle-Resolved Numerical Simulation implemented with a front-tracking method (capturing the particles’ interfaces) has been successfully carried out [1]. Results for a liquid–solid particle bed with more than 2000 particles under various fluidization configurations are in agreement with experimental results [2]. For gas–particle flows, due to a higher ρ\rhosolid/ρ\rhofluid density ratio, simulations become more challenging. To this date, several advancements have been made. Our method successfully simulates the fall and rebound against a wall of a solid particle in the air, under “reasonable” resolutions. In current development, we are simulating an air–particle fluidized bed as a way to fully solve wall-to-bed heat transfer in flow configurations representative of solar receivers. [1] Hamidi et al., Assessment of a coupled VOF-Front-Tracking/DEM method for simulating fluid–particles flows, Int. J. Multiph. Flow (2023). [2] Butaye et al., Development of Particle Resolved - Subgrid Corrected Simulations: Hydrodynamic force calculation and flow sub-resolution corrections, Comput. Fluids (2023).

Work In Progress