Full-field modeling of heat transfer in asteroid regolith: Radiative thermal conductivity of polydisperse particulates

Abstract

Characterizing the surface material of an asteroid is important for understanding its geology and for informing mission decisions, such as the selection of a sample site. Diurnal surface temperature amplitudes are directly related to the thermal properties of the materials on the surface. We describe a numerical model for studying the thermal conductivity of particulate regolith in vacuum. Heat diffusion and surface-to-surface radiation calculations are performed using the finite element (FE) method in three-dimensional meshed geometries of randomly packed spherical particles. We validate the model for test cases where the total solid and radiative conductivity values of particulates with monodisperse particle size frequency distributions (SFDs) are determined at steady-state thermal conditions. Then, we use the model to study the bulk radiative thermal conductivity of particulates with polydisperse, cumulative power-law particle SFDs. We show that for each polydisperse particulate geometry tested, there is a corresponding monodisperse geometry with some effective particle diameter that has an identical radiative thermal conductivity. These effective diameters are found to correspond very well to the Sauter mean particle diameter, which is essentially the surface-area-weighted mean. Next, we show that the thermal conductivity of the particle material can have an important effect on the radiative component of the thermal conductivity of particulates, especially if the particle material conductivity is very low or the spheres are relatively large, owing to non-isothermality in each particle. We provide an empirical correlation to predict the effects of non-isothermality on radiative thermal conductivity in both monodisperse and polydisperse particulates.

Accepted by Journal of Geophysical Research: Planets

References in corpus (1)

• Full-field modeling of heat transfer in asteroid regolith: Radiative thermal conductivity of polydisperse particulates

Cited by in corpus (9)

• The specific heat of astro-materials: Review of theoretical concepts, materials and techniques
• Full-field modeling of heat transfer in asteroid regolith: Radiative thermal conductivity of polydisperse particulates
• Low thermal conductivity of the superfast rotator (499998) 2011 PT
• Thermophysical Investigation of Asteroid Surfaces II: Factors Influencing Grain Size
• Thermal inertias of pebble-pile comet 67P/Churyumov-Gerasimenko
• Heat transfer in granular media with weakly interacting particles
• A method to distinguish between micro- and macro-granular surfaces of small Solar System bodies
• Analytic theory for the tangential YORP produced by the asteroid regolith
• Interpebble contact radius in a comet nucleus