Teaching thermal wave physics with soils

E. Marín, L.E. Jean-Baptiste, M. Hernández

Abstract


In this paper, we discuss the features of a possible student experiment related to the conduction of heat in soils excited by a natural periodically time dependent source, namely the daily periodical oscillations in the earth's temperature, which can be denoted as thermal waves. A measuring device was designed and constructed for automatic measurements of the daily time air temperature variations as well as of the daily time temperature variations, at different depths beneath the soil's surface. Measurements were performed using LM-335 solid state temperature sensors incorporated into a computer-controlled probe. The data acquisition software was developed using a programming environment LabVIEW from National Instruments. In order to obtain characteristic parameters governing the physical phenomena involved, the results of our measurements were fitted to a thermal wave like solution of the heat diffusion equation in the presence of periodical heat sources. The phase shift as well as the attenuation of the temperature waves with depth was demonstrated, as well as their dependence on soil thermal properties, in particular its thermal diffusivity.

Keywords


Thermal waves; soils; thermal properties; thermal diffusivity

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REVISTA MEXICANA DE FÍSICA E, year 18, issue 1, January-June 2021. Semiannual Journal published by Sociedad Mexicana de Física, A. C. Departamento de Física, 2º Piso, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, Alcaldía Coyacán, C.P. 04510 , Ciudad de México. Apartado Postal 70-348. Tel. (+52)55-5622-4946, https://rmf.smf.mx/ojs/rmf-e, rmf@ciencias.unam.mx. Chief Editor: José Alejandro Ayala Mercado.  INDAUTOR Certificate of Reserve: 04-2019-080216402500-203, ISSN: 2683-2216 (on line), 1870-3542 (print), both granted by Instituto Nacional del Derecho de Autor.  Responsible for the last update of this issue, Technical Staff of Sociedad Mexicana de Física, A. C., Fís. Efraín Garrido Román, 2º. Piso, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, Alcaldía Coyacán, C.P. 04510 , Ciudad de México. Date of last modification, January 04, 2021.

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