Thermal conductivity model for powdered materials under vacuum based on experimental studies

Abstract

The thermal conductivity of powdered media is characteristically very low in vacuum, and is effectively dependent on many parameters of their constituent particles and packing structure. Understanding of the heat transfer mechanism within powder layers in vacuum and theoretical modeling of their thermal conductivity are of great importance for several scientific and engineering problems. In this paper, we report the results of systematic thermal conductivity measurements of powdered media of varied particle size, porosity, and temperature under vacuum using glass beads as a model material. Based on the obtained experimental data, we investigated the heat transfer mechanism in powdered media in detail, and constructed a new theoretical thermal conductivity model for the vacuum condition. This model enables an absolute thermal conductivity to be calculated for a powder with the input of a set of powder parameters including particle size, porosity, temperature, and compressional stress or gravity, and vice versa. Our model is expected to be a competent tool for several scientific and engineering fields of study related to powders, such as the thermal infrared observation of air-less planetary bodies, thermal evolution of planetesimals, and performance of thermal insulators and heat storage powders. © 2017 Author (s)

Thermal conductivity and coordination number of compressed dust aggregates

“…We examine filling factor dependences of the coordination number Z and the thermal conductivity through the solid network k sol , and we derive empirical formulae of Z = Z(φ) and k sol = k sol (φ, Z(φ)). Then we confirm the validity of the results by comparison with the experimental data of Sakatani et al (2017). Our findings are expected to be competent tools for many fields of study related to dust aggregates and powdered media.…”

Scattering, absorption, and thermal emission by large cometary dust particles: Synoptic numerical solution

“…In our computations, the heat conduction coefficient is assumed to be κ = 0.00025 W/m/K, which corresponds to a realistic value for a porous dust aggregate (Krause et al 2011;Arakawa et al 2017;Sakatani et al 2017 coefficient depends on porosity, grain size, and composition. Increasing the heat conduction coefficient flattens the superheating phase functions.…”

Constraining the thermal properties of planetary surfaces using machine learning: Application to airless bodies

“…This is involves comparing theoretical values for regolith thermal conductivity at different particle sizes to thermal conductivity values derived from the predicted thermal inertia, leaving regolith porosity as a free parameter. In lieu of the particulate thermal conductivity model developed and utilized by Gundlach and Blum (2013), we instead utilize the improved model by Sakatani et al (2017) along with updated model tunable parameter values from the experimental work by Ryan (2018). The model by Sakatani calculates the solid and radiative components of the thermal conductivity of particulates as a function of relevant material and environmental parameters (Table 6).…”

“…Parameters ζ and ξ are used to tune the radiative and solid conduction components of the model, respectively, in order to fit the model to experimental measurements of particulate thermal conductivity. Sakatani et al (2017Sakatani et al ( , 2018 provide values for particulates up to approximately 1 mm in diameter. Recently, Ryan (2018) obtained values for the parameters from conductivity experiments for particles up to 1 cm in diameter.…”