Analysis of Near-Wall Pebble Bed Thermal Conductivity for Energy Applications

Katelyn Wada; Josh Eixenberger; Dallin Stout; Brian J Jaques; Todd Otanicar; David Estrada

doi:10.1021/acsomega.3c08202

Analysis of Near-Wall Pebble Bed Thermal Conductivity for Energy Applications

ACS Omega. 2023 Dec 28;9(1):1614-1619. doi: 10.1021/acsomega.3c08202. eCollection 2024 Jan 9.

Authors

Katelyn Wada¹, Josh Eixenberger^{1

2

3}, Dallin Stout⁴, Brian J Jaques^{1

2

5}, Todd Otanicar⁴, David Estrada^{1

2

5}

Affiliations

¹ Micron School of Materials Science and Engineering, Boise State University, Boise, Idaho 83725, United States.
² Center for Advanced Energy Studies, Boise State University, Boise, Idaho 83725, United States.
³ Department of Physics, Boise State University, Boise, Idaho 83725, United States.
⁴ Department of Mechanical and Biomedical Engineering, Boise State University, Boise, Idaho 83725, United States.
⁵ Idaho National Laboratory, Idaho Falls, Idaho 83415, United States.

Abstract

Pebble beds have been employed in thermal storage and energy systems, where they are typically used to promote heat exchange in high-temperature environments. Understanding the heat conduction of the entire pebble bed could aid in the material selection of the pebbles themselves and structural components, system design, and safety monitoring. However, the thermal conductivity of pebble beds can change significantly near geometric boundaries. Using a complex multilayer analytical model in conjunction with a line source probe, we found a substantial increase in the thermal conductivity of a sintered bauxite pebble bed in the near-wall region (7.6 W m^-1 K^-1) compared to the bulk (0.59 W m^-1 K^-1). We investigated this difference by comparing porosity results, acquired with micro-CT, of 33.18 and 33.31% at approximately one pebble width surrounding the probe (near-wall) and the bulk of the pebble bed, suggesting that the thermal conductivity is largely altered by thermal contact resistance in the near-wall regime.