Thermal diffusivity of peat-sand mixtures

Abstract

Thermal diffusivity of peat, quartz sand, and their mixtures was studied at different water contents using the unsteady-state method. Quartz content in studied samples was 0.00 m3m-3 (pure peat), 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.55, and 0.62 m3m-3 (pure sand). Thermal diffusivity of air-dry samples varied from 0.6×10-7 m2s-1 for pure peat to 7.0×10-7 m2s-1 for pure sand. Thermal diffusivity of moist samples grew by two-four times as compared to dry samples. Small amounts of quartz material with separate sand particles distributed within the peat didn't contribute much to the heat transfer through the studied media, and the thermal diffusivity of mixtures with quartz contents of 0.05 and 0.10 m3m-3 was practically the same as that for pure peat. Vice versa, there were pronounced differences in thermal diffusivities between the samples with quartz contents of 0.55 and 0.62 m3m-3. It means that addition of small amounts of peat to the sand material results in significant lessening of thermal diffusivity. We assume that there is a kind of threshold between the quartz contents of 0.10 and 0.15 m3m-3, after which the continuous sandy chains are formed within the peat, which can serve as preferential paths of heat transport.