Session: 03-04 Sensible Energy Storage

Paper Number: 116598

116598 - Heat Transfer Models of High-Temperature Gravity-Driven Granular Flows Between Vertical Parallel Plates for Solar Thermal Energy Storage and Transport 

Concentrated solar power (CSP) offers a sustainable path to produce electricity by utilizing vast solar resources and aid in the transition towards complete decarbonization of electricity production. The integration of thermal energy storage (TES) with CSP enables sensible solar energy storage to produce on-demand electricity and operation during solar transients and outside of diurnal periods. Particle-based TES is receiving increased attention due to a distinct advantage over widely used molten salts. Bauxite particles are of particular interest as a particle-based storage medium due to high solar absorptivity and ability to operate at temperatures up to 1000°C. Particle heat transfer and storage media is well-suited for driving higher efficiency power cycles (sCO₂ or Air Brayton cycles). The realization of an efficient particle-based heat exchanger to deliver the stored thermal energy from TES to working fluid is necessary for enabling continuous electricity production with high efficiency. Gravity-driven moving packed-bed heat exchangers hold strong advantage in operational costs compared to other heat exchangers (e.g., fluidized-bed heat exchangers, which require additional pumping costs to realize fluidization). Heat transfer between particles and the wall decreases and leads to challenges to meet required thermal performance due to reduced mixing of particles. A fundamental understanding of heat transfer between heated particles and the wall is required because granular flows at elevated temperatures. Granular flows between narrow parallel plates are very important for informing the next generation of heat exchanger designs, necessitating a more basic understanding of the heat transfer mechanisms. A predictive heat transfer model integrating temperature-dependent flow behaviors is required to build cost-effective packed-bed heat exchanger that meet thermal duty demands. Experimentation was performed in an experimental rig with heated Carbobead CP 30/60 particles introduced between a two parallel plates in gravity-driven flows. Free-surface velocity and temperature fields were measured for flows up to 800 °C. Discrete element method (DEM) modeling in LIGGGHTS was performed using temperature-dependent flow properties and predicted free-surface velocity were compared to measurements along with mass flow rates. The DEM model was then exercised to examine spatial and temporal particle volume fractions and velocities within the flows. A numerical heat transfer model integrating temperature-dependent spatial particle velocities and volume fractions was developed in MATLAB. An ordinary equation solver was used to numerically integrate the system of differential energy equations through space (flow direction). The near-wall heat transfer was modeled based on thin film conduction mechanism using the simulated near-wall void fractions. Radiative heat transfer from heated particles to the wall was considered and due to low particle volume fraction within the channel, view factors from particle to wall were set to unity.

Presenting Author: Shin Young Jeong Georgia Tech

Presenting Author Biography: Shin Young Jeong is a PhD graduate student in Mechanical Engineering at Georgia Institute of Technology. He is supervised by Dr. Zhuomin Zhang and Dr. Peter Loutzenhiser. He have participated in Generation 3 Concentrated Solar Power projected funded by DOE. In this project, he have focused on characterizing radiative and flow properties of bauxite particles. Also, particle flow characterization and modeling at high temperature were also performed.