Thermal conductivity measurements of particulate materials 2. Results

Marsha A. Presley, Philip Christensen

Research output: Contribution to journalArticle

176 Citations (Scopus)

Abstract

A line-heat source apparatus was assembled for the purpose of measuring thermal conductivities of particulate samples under low pressures of a carbon dioxide atmosphere. The primary result of this project is the compilation of the first comprehensive suite of measurements of the dependence of thermal conductivity on particle size. The. thermal conductivity increases with increasing particle size and atmospheric pressure. In particular, over the range of Martian atmospheric pressures, from 1 to 7 torr, the thermal conductivity was found to be empirically related to approximately the square root of the particle diameter and the square of the cubed root of the atmospheric pressure. At the average pressure of the Martian surface (6 torr) the thermal conductivity varies from 0.011 W/m K, for particles less than 11 μm in diameter, to 0.11 W/m K, for particles 900 μm in diameter. These results differ significantly from the particle size dependence estimated for Mars from previous measurements, except for 200-μm particles, whose thermal conductivity is 0.053 W/m K. The thermal conductivities of larger particles are lower than the previous estimate, by 40% at 900 μm, and the thermal conductivities of smaller particles are higher than the previous estimate, by 60% at 11 μm. These newer estimates agree with other lines of evidence from Martian atmospheric and surficial processes and lead to improved particle size estimates for most of the planet's surface.

Original languageEnglish (US)
Article number96JE03303
Pages (from-to)6551-6566
Number of pages16
JournalJournal of Geophysical Research E: Planets
Volume102
Issue numberE3
StatePublished - 1997

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thermal conductivity
particulates
Thermal conductivity
Particle size
particle size
atmospheric pressure
Atmospheric pressure
estimates
material
Planets
heat source
Carbon Dioxide
particle
low pressure
Mars
heat sources
planet
carbon dioxide
mars
planets

Keywords

  • 1-Butanethiol
  • 2-Butanethiol
  • Branching ratio
  • Fragmentation mechanism
  • Inner-shell excitation
  • Ion pair formation
  • Kinetic
  • PEPICO
  • Selective photoion-photoion coincidence
  • Trichlorofluoromethane

ASJC Scopus subject areas

  • Oceanography
  • Astronomy and Astrophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

Thermal conductivity measurements of particulate materials 2. Results. / Presley, Marsha A.; Christensen, Philip.

In: Journal of Geophysical Research E: Planets, Vol. 102, No. E3, 96JE03303, 1997, p. 6551-6566.

Research output: Contribution to journalArticle

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abstract = "A line-heat source apparatus was assembled for the purpose of measuring thermal conductivities of particulate samples under low pressures of a carbon dioxide atmosphere. The primary result of this project is the compilation of the first comprehensive suite of measurements of the dependence of thermal conductivity on particle size. The. thermal conductivity increases with increasing particle size and atmospheric pressure. In particular, over the range of Martian atmospheric pressures, from 1 to 7 torr, the thermal conductivity was found to be empirically related to approximately the square root of the particle diameter and the square of the cubed root of the atmospheric pressure. At the average pressure of the Martian surface (6 torr) the thermal conductivity varies from 0.011 W/m K, for particles less than 11 μm in diameter, to 0.11 W/m K, for particles 900 μm in diameter. These results differ significantly from the particle size dependence estimated for Mars from previous measurements, except for 200-μm particles, whose thermal conductivity is 0.053 W/m K. The thermal conductivities of larger particles are lower than the previous estimate, by 40{\%} at 900 μm, and the thermal conductivities of smaller particles are higher than the previous estimate, by 60{\%} at 11 μm. These newer estimates agree with other lines of evidence from Martian atmospheric and surficial processes and lead to improved particle size estimates for most of the planet's surface.",
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