title: Thermal separation of soil particles from thermal conductivity measurement under various air pressures.
abstract: The thermal conductivity of dry soils is related closely to air pressure and the contact areas between solid particles. In this study, the thermal conductivity of two-phase soil systems was determined under reduced and increased air pressures. The thermal separation of soil particles, i.e., the characteristic dimension of the pore space (d), was then estimated based on the relationship between soil thermal conductivity and air pressure. Results showed that under both reduced and increased air pressures, d estimations were significantly larger than the geometrical mean separation of solid particles (D), which suggested that conductive heat transfer through solid particles dominated heat transfer in dry soils. The increased air pressure approach gave d values lower than that of the reduced air pressure method. With increasing air pressure, more collisions between gas molecules and solid surface occurred in micro-pores and intra-aggregate pores due to the reduction of mean free path of air molecules. Compared to the reduced air pressure approach, the increased air pressure approach expressed more micro-pore structure attributes in heat transfer. We concluded that measuring thermal conductivity under increased air pressure procedures gave better-quality d values, and improved soil micro-pore structure estimation.
authors.affiliation: Key Laboratory of Tree Breeding and Cultivation of the State Forestry Administration, Research Institute of Forestry, Beijing 100091, China.|Co-Innovation Center for Sustaintable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China.
authors.forename: Sen
authors.initials: S
authors.lastname: Lu
authors.affiliation: Department of Soil and Water, China Agricultural University, Beijing 100193, China.
authors.forename: Tusheng
authors.initials: T
authors.lastname: Ren
authors.affiliation: Department of Soil and Water, China Agricultural University, Beijing 100193, China.
authors.forename: Yili
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Key Laboratory of Tree Breeding and Cultivation of the State Forestry Administration, Research Institute of Forestry, Beijing 100091, China.|Co-Innovation Center for Sustaintable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Meng
authors.affiliation: Key Laboratory of Tree Breeding and Cultivation of the State Forestry Administration, Research Institute of Forestry, Beijing 100091, China.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Zhang