Thermal conductivities of Wood Ash Diatomite and their composite mixtures

Abstract

The transient hot-strip (THS) method was used to investigate the thermal conductivities of samples in their consolidated or moulded forms. Two different porous materials, i.e., wood ash and diatomite (F and Bu types), as well as their composite mixtures were used in this investigation. The samples were grouped in various particle sizes. their porosities determined, and their physical as well as chemical characteristics discussed. Thermal conductivity variations of the samples, with the factors; particle size, porosity, moisture content, composition of the mixtures and temperature were investigated. F diatomite samples in general displayed high thermal conductivity values of up to 8.92 X lO‘2 W m'1 K-1 at room temperature and 0 % moisture content. There were low values for wood ash, 2.25 x lO'2 W m‘l K4, while Bu diatomite displayed moderate \'alues for the same conditions. In comparison with the pure samples, the composite mixtures of wood ash, Bu and F diatomite showed very low values These ranged from 1.26 x 10'; W m'] K4, for the 75 % wood ash/ 25 % Bu composite, to 6.796 x 10': W m'1 K" for the 50 % F/ 20 % Wood ash/ 30 % Bu composite mixture. A comparison of these results obtained using the THS method, and those obtained in theoretical models of determination of thermal conductivities of porous media shows satisfactory agreement. These materials could be used as thermal insulators and fluid adsorbents mainly due to there well defined porosities, wide pore size distribution and ability to retain moisture. The interlock between individual particles in the composites provides a possibility of the composites to be used as fillers and binders.