Session: 06-02: Heat Transfer in CSP Applications 1

Paper Number: 138520

138520 - Locally Fluidized Moving Bed Particle Heat Exchanger for Concentrating Solar Power 

Abstract: 

Solid-particle heat exchangers (HXs) enable thermal energy storage at temperatures exceeding 700°C without the complications associated with phase change, making them ideally suited for Concentrating Solar Power (CSP) applications. In addition to thermal energy storage, the existing types of solid-particle heat exchangers used in CSP power towers utilize solid media (such as sand) as the working fluid during operation. These HXs are classified into gravity-driven (such as shell-and-tube and shell-and-plate) where the working fluid in a moving bed falls through a tube bank and interacts with the tube walls, and forced-convection (such as fluidized bed), where the working fluid is compelled to interact with the wall of the tube bank by air pressure. Each type possesses distinct advantages. While gravity-driven configurations are scalable and cost-effective, forced-convection configurations achieve higher heat transfer coefficients. Combining these advantages in a single configuration is challenging mainly due to the distinct solid-particle flow patterns around the tube bank. This work demonstrates a multi-stage locally fluidized moving bed HX design that combines the scalability and cost-effectiveness of the gravity-driven configuration with the heat transfer performance of the forced-convection configuration. This research employs a custom see-trough multi-stage test rig capable of multidirectional fluidization and a high-speed camera to document and study the multiphase interaction of compressed air- and gravity-driven sand flow around circular tubes in different stages through Particle Image Velocimetry (PIV). With this hybrid approach, we show the ability to control characteristics of the forced-convection configuration (including fluidization intensity and directionality through a variety of pressure inputs and nozzle geometries), as well as  the gravity-driven configuration (including discharge rates between stages using perforated plates with different hole diameters and retention time of the falling solid media) allowing both flow patterns to develop and interact in each stage aiming to prolong the particle-to-wall contact demonstrating the potential to achieve heat transfer coefficients similar to forced-convection configurations. In addition to the experimental approach, we use Ansys-Fluent, to develop a Computational Fluid Dynamics (CFD) Eulerian-Eulerian simulation that visualizes the multiphase flow behavior, calculates discharge rates for different perforated plate configurations and finally evaluate the local heat transfer coefficients around the tube walls in different CSP HX scenarios. Our results indicate a potential of our novel locally fluidized moving bed approach to increase the average particle-to-wall heat transfer coefficient by 50%, relative to the conventional gravity-driven shell-and-tube configuration. This work could improve our understanding of particle flow behavior under gravity and forced-convection conditions, potentially enabling the development of low-cost high-performance HXs for CSP and other applications.

Presenting Author: Julio Izquierdo university of louisville

Presenting Author Biography: He is currently a Ph.D. candidate in mechanical engineering and is a member of the Pyro-Electric Research Lab (PERL). His research focuses on combining modeling and testing to improve and characterize high temperature heat exchangers employed in solar energy generation. In 2022, he was selected by the committee of mechanical engineering professors as the first awardee of the Ed Toutant fellowship that is meant to support highly qualified Ph.D. students in the mechanical engineering program.

Research Interests:
• Energy generation and storage
• Computational Fluid Dynamics
• Additive Manufacturing of different materials

Authors:

Julio Izquierdo university of louisville
Bikram Bhatia University of Louisville