Thermal conductivity of selected claystones and mudstones from England

Abstract

The claystones and mudstones investigated are London Clay, Fullers Earth, Oxford Clay and Kimmeridge Clay. The thermal conductivities were measured using a divided bar apparatus and the values measured perpendicular to layering ranged from 0.68 to 0.97 W/mK. Comparative measurements of thermal conductivities were carried out by the needle probe method and Middleton's method. Deviations of up to 50% were obtained between the needle probe and the divided bar method. The thermal conductivities estimated from the geometric mean model based on mineralogy and water content ranged from 0.87 to 2.01 W/mK, considerably higher than the measured values. A correlation was found between the grain size distributions of the samples and the measured thermal conductivities. This textural effect on the thermal conductivity is assumed to be the main reason for the low measured values and the lack of correlation between the measured and the calculated values.

On the determination of thermal conductivity of sedimentary rocks and the significance for basin temperature history

“…On the other hand, Midttømme et al (1998a) assumed that a grain-size effect could be the main reason for the lack of correlation between the mineralogy-based models and the measurements. This was supported by studies of sand and silt/clay fractions of the same rock: the clay and silt fraction has a lower thermal conductivity than sand (Rzhevsky & Novik 1971;Midttømme & Roaldset 1998).…”

Spontaneous self-combustion of organic-rich lateglacial lake sediments after freeze-drying

“…We assume this from the observed pulsating propagation of the combustion through the sample, caused by the regular slowdown of the burning in Chara layers. The self-sustaining of the combustion might have been additionally favoured by the high abundance of siderite crystals since siderite has a low thermal conductivity (j = 3; Midttomme et al 1998;Horai 1971). One might speculate that this caused reduced heat loss and, therefore, heat accumulation in the sediment further favouring the burning process.…”

Laser transmission welding of poly(lactic acid) and polyamide66/sepiolite nanocomposites

“…Mechanical, thermal, and volumetric properties of materials involved in this work were obtained from bibliographic data and by means of using different approach. 14,[34][35][36][37] Young's modulus (E) and melting temperature (T m ) of pure polyamide and nanocomposites with different sepiolite loading were obtained from previous work. 14 Linear mixing rule [eq.…”

“…Specific volume, thermal conductivity and heat capacity of sepiolite (v f , k f, c f ) were obtained from literature. 35,36 Moulded specimens were optically characterized in terms of reflectance, absorbance, and transmittance in a FT-NIR Analyzer (Antaris, Nicolet, United States) equipped with both a transmission and a reflection module in order to determine the suitability of the materials for being used in LTW. Five sample of each material were analyzed in the spectral range 25,000-7,812 nm at 64 scan to get an average value of reflectance (R), absorbance (A), and transmittance (T) at 980 nm, the wavelength of the laser used to carry out the laser welding processes of this work.…”

“… where v p and v f are the specific volume of the polymer matrix and filler, respectively; λ p and λ f are the thermal conductivities of the polymer matrix and filler, respectively; Ø is the volume fraction of sepiolite; c p and c f are the heat capacities of polymer matrix and filler, respectively, and X is the mass fraction of sepiolite. Specific volume, thermal conductivity and heat capacity of sepiolite ( v f , λ f , c f ) were obtained from literature …”