Session: 05-04: Concentrating Solar Power I -- Receiver Simulations/Analysis

Paper Number: 131392

131392 - Optical Flow Diagnostics of Counter Fluidization of Gravity-Driven Moving Packed Bed for a CSP Receiver Section Featuring Staggered Array of Cylindrical Pins 

Abstract: 

Concentrated solar power (CSP) plants with thermal energy storage (TES) are promising renewable energy technologies that can provide clean electricity at utility scales. However current CSP-TES technology relies on molten salt to store thermal energy which is limited to temperatures below 565 ֯C, restricting their efficiency and competitiveness with photovoltaic (PV) technology and fossil fuels. Next generation CSP technology (Gen-3 CSP) aims to reach temperatures exceeding 700֯C by using solid particles as heat transfer medium coupled with supercritical carbon dioxide (sCO₂) Brayton cycle for power generation. Particles such as silica sand and sintered bauxite are good candidates due to their thermal stability at elevated temperatures and their flowability. However, the particles’ low thermal conductivity and low order of mixing in an undisturbed moving packed bed between two parallel plates results in reduced heat transfer. Fluidization of moving packed bed has the potential to enhance heat transfer between particles and the walls by increasing particle mixing by agitation through the introduction of counter moving flow. The fluidization behavior at the heat transfer surface is critical to the performance of the beds.  The present study is focused on the hydrodynamics of moving packed bed of silica particles in a representative receiver module. The flow visualization is performed on the surface of transparent glass coated with electrically conductive materials for electrostatic dissipation purposes. Images of the fluidized bed are taken with the help of a high definition and high-speed camera at frequency of 1069 Hz. The images captured the multiphase flow patterns within the fluidized bed with varying fluidization velocities. The images are analyzed in pairs with the help of a modern optical flow algorithm capable of calculating the movement of dense particle flow in the fluidized bed by tracking the light intensity of the images in predefined window within the frames. Quantitative flow-field data was extracted by applying the Farneback optical flow algorithm. This methodology resulted in detailed velocity magnitude and velocity vector that enabled tracking of bubbles/voids in the test section due to fluidization. The results from this setup and analysis technique can be used to experimentally characterize the impact of fluidization velocity, particle size, and distributor design the bubble behavior and flow non-uniformities. Besides concentrated solar power applications, the presented experimental approach and flow analysis technique can provide insights into the fundamentals of gas-solid fluidization hydrodynamics. The quantitative whole-field data can be used to validate numerical simulations and develop improved models of fluidized bed systems.

Presenting Author: Youssef Aider University of Tennesse Knoxville

Presenting Author Biography: Youssef Aider is a graduate research assistant at the University of Tennessee Knoxville

Authors:

Youssef Aider University of Tennesse Knoxville
Zhiwen Ma National Renewable Energy Laboratory
Prashant Singh University of Tennessee Knoxville