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Research Papers: Conduction

Determination of the Thermal Conductivity in Adobe With Several Models

[+] Author and Article Information
P. Mosquera

e-mail: pablomosquera@terra.com

J. Cid-Falceto

Research group PADOC (Patrimony, Landscape,
Graphic Documentation and Agroforestry
Construction)
Esc. Técnica,
Superior de Ingenieros Agrónomos,
Universidad Politécnica de Madrid, s/n
28040 Madrid, Spain

F. Marcos

Thermodynamics, Engines and Forestry Machinery,
Esc. Técnica,
Superior de Ingenieros de Montes,
Universidad Politécnica de Madrid,
Ciudad Universitaria,
s/n. 28040 Madrid, Spain

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received March 6, 2013; final manuscript received August 5, 2013; published online November 28, 2013. Assoc. Editor: Oronzio Manca.

J. Heat Transfer 136(3), 031303 (Nov 28, 2013) (10 pages) Paper No: HT-13-1116; doi: 10.1115/1.4025560 History: Received March 06, 2013; Revised August 05, 2013

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 (λE) 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 λE in adobes. The λE 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 °C and 41% of relative moisture, the values of λE measured were 0.80 W/(m·K) ± 10%. For natural hygroscopic moisture of 1.67% in the same environmental conditions, a λE of 0.90 W/(m·K) ± 10% 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.

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References

Figures

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Fig. 1

X-ray diffractometry

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Fig. 4

Evolution of the temperature during the measurement time

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Fig. 3

Diagram of the needle in contact with the porous material

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Fig. 2

Measurement device of thermal conductivity

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Fig. 5

Sketch for components in series

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Fig. 6

Sketch for components in parallel

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Fig. 8

MA-2 model: thermal conductivity as a function of the density

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