IOP Conference Series: Materials Science and Engineering
Clay is an ecological building material used widely in constructions especially in rural areas. I... more Clay is an ecological building material used widely in constructions especially in rural areas. In this work an experimental study has been carried out to estimate the apparent thermal diffusivity and adiabatic limit temperature of three types of unfired clay brick using flash method. The three samples were prepared with the same water proportion (picked between the plasticity and the liquidity limits) and exposed to the same drying conditions. The thermal diffusivity and adiabatic limit temperature were estimated using numerical global minimization procedures of the quadratic distance between the theoretical model and the experimental thermogram. The theoretical model is derived from a numerical inversion of Laplace transform using Gaver-Stehfest method. An approach based on the independence between the sensitivity coefficients and the magnitude of these coefficients(Beck criterion)is presented in order to examine the simultaneous estimation of the different parameters related to the theoretical model from the experimental data. For all samples tested, the results show that the estimated parameters give a good agreement between the experimental data and the theoretical model.
IOP Conference Series: Materials Science and Engineering
Thermophysical properties of building materials such as thermal conductivity and thermal diffusiv... more Thermophysical properties of building materials such as thermal conductivity and thermal diffusivity are mandatory in any study of thermal performance of buildings. In this work, measurements of these two thermophysical properties were performed on four circular samples prepared by mixing gypsum plaster with different mass proportions of expanded clay granules. The water ratio was kept constant in all mixtures. Then the thermal diffusivity and thermal conductivity were determined using the flash method and the hot plate respectively. Results show that the addition of the expanded clay granules to the gypsum plaster has a negative impact on the thermal properties. This was due to absorption of the mix water and plaster by the clay granulates at the earlier operation of samples preparation.
IOP Conference Series: Materials Science and Engineering
A new exploitation of the Hot Plate in Steady state HPS on the determination of thermal conductiv... more A new exploitation of the Hot Plate in Steady state HPS on the determination of thermal conductivity variation with temperature is presented. The mean temperature changement with temperature of the tested sample is ensured with varying the value of the voltage applied to the hot plate resistance, which enables to measure the thermal conductivity in different temperatures. Calculated thermal conductivity values obtained using a gypsum plaster sample, which specific heat capacity variation with temperature is accurately measured, validate the technic. Results show that the mean calculated thermal conductivity of the studied gypsum plaster is 0,143 W/m.k while the measured one is 0,148 W/m.k with a mean deviation of 3,81%. Moreover, the two trend lines of measured values and calculated ones have the same slope with a small intercept difference of 0,004.
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Papers by Saad Raefat