Determination of the Thermal Conductivity in Adobe With Several Models

摘要

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 MA-1 and MA-2) to calculate the effective thermal conductivity (λ_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 MA-1 starts from the electric analogy of the transmission of heat in series and in parallel. The model MA-2 is obtained with a regression curve from experimental and literature values of λ_E in adobes. The λ_E in adobes has been measured by the thermal needle probe (TNP) procedure using 10min as the measuring time. For dry adobes, with average environmental conditions of 19°C and 41% of relative moisture, the values of λ_E measured were 0.80W/(m·K) ± 10%. For natural hygroscopic moisture of 1.67% in the same environmental conditions, a λ_E of 0.90 W/(m·K) ± 70% was measured. Only five of the 18 models analyzed adjust to the values experimentally measured, and their precision depends on the values of λ of the components, which are obtained from the literature. Of the proposed models, the MA-1 fits for the values of the dry and wet material and with some determined values of the literature. The model MA-2 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.