A Monte Carlo method to solve for radiative effective thermal conductivity for particle beds of various solid fractions and emissivities

The research article “A Monte Carlo method to solve for radiative effective thermal conductivity for particle beds of various solid fractions and emissivities”, co-authored by METU members Prof. İlker Tarı and Prof. Derek Keith Baker, has been published in Journal of Quantitative Spectroscopy and Radiative Transfer.

A method is described to find the effective thermal conductivity due to radiation (krad) for groups of particles at packed and less than packed states. Unlike most previous studies, the method does not rely on the assumption of a unit cell or absorption and scattering coefficients to derive krad. In this method, radiation is modeled with a 3D Monte Carlo ray tracing code, steady state particle temperatures are found with a particle-particle heat exchange simulation, and krad is found with a comparison to heat conduction in an isotropic solid of the same geometry. This leads to the dimensionless Exchange Factor (FE), allowing krad to be calculated at any temperature and particle radius. The key result is a model for FE over the entire range of emissivities from 0.3 to 1 and solid fractions from 0.25 to the fully packed state of 0.64. FE results are compared to previous models, with agreement shown in some cases but a large disagreement found for low solid fractions. The krad results are combined with the Zehner and Schlünder model for solid and fluid conduction, providing an equation for the full effective thermal conductivity.

Johnson, E., Tarı, İ., & Baker, D. (2020). A monte carlo method to solve for radiative effective thermal conductivity for particle beds of various solid fractions and emissivities. Journal of Quantitative Spectroscopy and Radiative Transfer, 250 doi:10.1016/j.jqsrt.2020.107014

Article access: https://www.sciencedirect.com/science/article/pii/S0022407320301011?via%3Dihub

Keywords:

Heat transfer in particle beds; Monte Carlo; Particle-particle radiation; Radiation between spheres; Radiative effective thermal conductivity; Radiative exchange factor

Other authors:
Johnson, E. (METU)

Acknowledgments:
This work was supported with funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 731287 for the project Integrating National Research Agendas on Solar Heat for Industrial Processes (INSHIP).