Investigation of mechanical and thermal properties of sintered bauxite and sand particles as heat transfer and storage media

Uykun, Zeynep
Solid particles have gained an attraction in recent years to be used as a heat transfer and storage medium that can be integrated into various thermal power plants. Particles operate in a closed-loop cycle in the power plants such as Concentrating Solar Power (CSP); firstly, they are heated up in the receiver then carried to the storage system and they discharge their energy to the thermodynamic-cycle. Discrete Element Method (DEM) has been gaining importance for modeling particle-based heat transfer and storage systems such as CSP and its components. DEM predicts the bulk particle behaviour more accurately than continuum models. To properly model the particles as a bulk, exact individual particle properties should be inputted to DEM models. Properties of candidate particles that are input to DEM are investigated in this study. Two of the popular candidate particles which are CarboHSP 40/70 and sand are examined in terms of mechanical and thermal characteristics. Particle-particle and particle-wall rolling and sliding frictions and restitution coefficients of candidate particles are investigated. The inclined plane test was performed for the investigation of the particle-wall friction coefficient. The discharged test was utilized for the v calibration of other parameters. Inter-particle friction coefficients were calibrated by Angle of Repose (AOR) and discharged mass measurement. A new useful calibration method for the investigation of the restitution coefficient is presented. This method suggests the scattering measurement of particles after discharge. Particle-wall and inter-particle restitution coefficients of examined particles are investigated by utilizing this method. Solid particles are in a thermal cycle as heat transfer and storage medium in related systems by heating up and cooling down. To meet this case, particles were cycled in a furnace many times from room temperature to 700 °C and calibration tests with repeated with cycled particles. Also, the discharge test was repeated with hot particles up to 600 °C. Particle properties, as well as particle resistance, were checked in this way. Hot Disk measurement device was used for thermal characterization of the particles from room temperature to elevated temperatures. Sensor bias was corrected at high-temperature measurements with Mica sensor to avoid overestimation of properties. Specific heat capacity and bulk thermal conductivity of the candidate particles were measured and reported.
Citation Formats
Z. Uykun, “Investigation of mechanical and thermal properties of sintered bauxite and sand particles as heat transfer and storage media,” M.S. - Master of Science, Middle East Technical University, 2021.