Measuring of Thermal Conductivities of Soils and Rocks to Be Used in the Calculation of A Geothermal Installation

• Published in: Energies (Basel) Vol. 10; no. 6; p. 795
• Main Authors: Sáez Blázquez, Cristina, Farfán Martín, Arturo, Martín Nieto, Ignacio, Gonzalez-Aguilera, Diego
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-06-2017
• Subjects: Aluminum; Cold; Composite materials; Conductivity; Earth Energy Designer (EED); Error analysis; Fourier law; Fractals; Guarded Hot Plate method; Heat conductivity; Heat transfer; Laboratories; Rocks; Soil sciences; Specific heat; Temperature; Thermal conductivity; Thermal Response Test (TRT); very low enthalpy geothermal installation; United States > US; Spain
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en10060795

From Q˙x value and considering the steady temperatures, the dimensions of sample S and Equation (1), thermal conductivity of the sample S can be easily calculated [26,27]. [...]by the implementation of the procedure detailed in the present paper, it is viable to obtain the value of thermal conductivity of a particular material S. Equations (1) and (2) can be obtained based on Fourier’s law. Graphically, taking from the graphic in Figure 9 two temperatures and the corresponding values of thermal conductivity according to the curve represented in region III, it is possible to establish the reduction of thermal conductivity with the temperature in that region. [...]if we select the temperatures of 95 K and 100 K, we can verify the decrease of thermal conductivity with an increase of temperature of 5 K. In this way, and according to Debye’s graphical, for the temperature of 95 K, the corresponding value of thermal conductivity is 2.01 W/mK, while for 100 K the value of thermal conductivity is 1.87 W/mK. The optimal dimensions of the sample S could be established based on the results of these measurements. [...]analyzing Table 4, it can be observed that, for the three temperatures, the values of thermal conductivity for each of the thickness are around the same value (~2 W/mK). [...]instead of the thermal conductivity value of 3 W/mK provided by the CTE for a granite rock, an interval of 2.0 W/mK–3.8 W/mK was taken for quartz contents between 3% and 50%.