Mediate relation between electrical and thermal conductivity of soil
- PDF / 573,124 Bytes
- 16 Pages / 547.087 x 737.008 pts Page_size
- 83 Downloads / 256 Views
(2020) 6:50
(0123456789().,-volV) ( 01234567 89().,-volV)
ORIGINAL ARTICLE
Mediate relation between electrical and thermal conductivity of soil Hans Schwarz
. David Bertermann
Received: 5 April 2020 / Accepted: 9 July 2020 Ó The Author(s) 2020
Abstract Thermal conductivity is a key parameter for many soil applications, especially for dimensioning shallow and very shallow geothermal systems based on the possible heat extraction rate and for modelling heat transfer processes around high voltage underground cables. Due to the limited purview of direct thermal conductivity measurements, for an investigation of extensive areas, usually other geophysical methods like electrical resistivity tomography measurements are applied. To derive thermal conductivity of soil from geoelectrical measurements a relation between electrical and thermal conductivity is needed. Until now only few approaches worked on a direct correlation between both conductivities. Due to the difficulties of a direct relation, within this study a modular approach of a mediate correlation between electrical and thermal conductivity was investigated. Therefore, a direct relationship between a corrected electrical conductivity and water content as well as the standard and simple thermal conductivity model of Kersten (Bull of the Univ Minnesota 28:1–227, 1949) was used. To develop this concept soil types of sand, silt loam and clay were investigated where different saturation steps and pressure loads were applied. For each configuration electrical and thermal conductivity
H. Schwarz (&) D. Bertermann Geo-Centre of Northern Bavaria, Friedrich-Alexander University Erlangen-Nuremberg, Schlossgarten 5, 91054 Erlangen, Germany e-mail: [email protected]
as well as water content and bulk density was determined. To refine the results of the calculated water content a corrective factor was applied. Furthermore, bulk density as an inlet parameter of the Kersten equation was also derived based on electrical conductivity. The suggested proceeding enables the determination of thermal conductivity solely based on electrical conductivity without prior soil property information. Keywords ERT Heat transfer Kersten model Water content Bulk density
1 Introduction Thermal conductivity (TC), which is a valuable soil parameter especially within the subjects of shallow and very shallow geothermal applications (Bertermann et al. 2014; Sa´ez Bla´zquez et al. 2017; Vieira et al. 2017; Di Sipio and Bertermann 2018) and high voltage underground cable surroundings (de Lieto et al. 2014; Salata et al. 2016; Chatzipanagiotou et al. 2017; Drefke et al. 2017; Rerak and Oclon 2017), is tricky to determine accurately in the field. Since, thermal conductivity itself can only be determined by sensors with direct contact at selective points of interest, indirect proceedings concerning other geophysical applications like electrical resistivity
123
50
Page 2 of 16
Geomech. Geophys. Geo-energ. Geo-resour.
tomography (ERT) are needed to examine wide areas in a small timefr
Data Loading...
