NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
A Model of Thermal Conductivity for Planetary Soils: 1. Theory for Unconsolidated SoilsWe present a model of heat conduction for mono-sized spherical particulate media under stagnant gases based on the kinetic theory of gases, numerical modeling of Fourier s law of heat conduction, theoretical constraints on the gas thermal conductivity at various Knudsen regimes, and laboratory measurements. Incorporating the effect of the temperature allows for the derivation of the pore-filling gas conductivity and bulk thermal conductivity of samples using additional parameters (pressure, gas composition, grain size, and porosity). The radiative and solid-to-solid conductivities are also accounted for. Our thermal model reproduces the well-established bulk thermal conductivity dependency of a sample with the grain size and pressure and also confirms laboratory measurements finding that higher porosities generally lead to lower conductivities. It predicts the existence of the plateau conductivity at high pressure, where the bulk conductivity does not depend on the grain size. The good agreement between the model predictions and published laboratory measurements under a variety of pressures, temperatures, gas compositions, and grain sizes provides additional confidence in our results. On Venus, Earth, and Titan, the pressure and temperature combinations are too high to observe a soil thermal conductivity dependency on the grain size, but each planet has a unique thermal inertia due to their different surface temperatures. On Mars, the temperature and pressure combination is ideal to observe the soil thermal conductivity dependency on the average grain size. Thermal conductivity models that do not take the temperature and the pore-filling gas composition into account may yield significant errors.
Document ID
20110014949
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Piqueux, S. (Arizona State Univ. Tempe, AZ, United States)
Christensen, P. R. (Arizona State Univ. Tempe, AZ, United States)
Date Acquired
August 25, 2013
Publication Date
September 22, 2009
Publication Information
Publication: Journal of Geophysical Research
Volume: 114
Subject Category
Geophysics
Report/Patent Number
E09005
Funding Number(s)
CONTRACT_GRANT: NNX07AQ35G
Distribution Limits
Public
Copyright
Other