Determination of the Thermal Conductivity in Adobe With Several Models

Abstract

The thermal conductivity of the earth materials conditions their ability as thermal isolator and its heating capacity, which has a direct impact on the energy consumption of the buildings built with these materials. Two original mathematical models have been developed (models MA1 and MA2) to calculate the effective thermal conductivity (خ»E) of adobes and their results have been compared with other models already known for other materials and with experimental measures done on adobes. The model MA1 starts from the electric analogy of the transmission of heat in series and in parallel. The model MA2 is obtained with a regression curve from experimental and literature values of خ»E in adobes. The خ»E in adobes has been measured by the thermal needle probe (TNP) procedure using 10 min as the measuring time. For dry adobes, with average environmental conditions of 19 آ°C and 41% of relative moisture, the values of خ»E measured were 0.80 W/(mآ·K) آ±â€‰10%. For natural hygroscopic moisture of 1.67% in the same environmental conditions, a خ»E of 0.90 W/(mآ·K) آ±â€‰10% was measured. Only five of the 18 models analyzed adjust to the values experimentally measured, and their precision depends on the values of خ» of the components, which are obtained from the literature. Of the proposed models, the MA1 fits for the values of the dry and wet material and with some determined values of the literature. The model MA2 fits in all cases since it does not depend on the values of the literature but on the density of the material and its moisture content.