Effect of Temperature on the Thermal Conductivity of Rocks and Its Implication for In Situ Correction

Abstract

Detailed knowledge of the effects of temperature on the thermal conductivity ( λ ) of rocks is essential for investigating the geothermal regime of basins and their thermal evolution. In this study, the λ of four rock types (carbonate, clastic, intrusive, and volcanic rocks) were measured at temperatures of 25°C, 50°C, 100°C, 150°C, 200°C, 250°C, and 300°C using the Transient Plane Source (TPS) approach, which is accurate to ±3%. Experimental results demonstrate that the λ of carbonate and clastic specimens decrease strongly with increasing temperature. In contrast, the λ of intrusive and volcanic rocks are relatively insensitive to temperature. The temperature ( T ) dependence of λ can be classified into three groups in terms of the value of λ at 25°C. The first group is composed of rocks characterized by high λ (>4.5 W/m·K) at room temperature, for which the curves of λ − T exhibit a concave pattern. The second group consists of rocks with a moderate λ (2.5~3.5 W/m·K), in which the curves tend to be a straight line. The last group comprises rocks with a low λ (<2.5 W/m·K), exhibiting convex curves. There exists a close relationship between the λ at 25°C and its rate of decrease ( α ). The absolute value of α increases with the λ at 25°C rising. The relationship between the two values can be fitted by the equation y = a x + b 1 / x + c to derive the fitting parameters a , b , and c ; by this equation with known fitting parameters, the λ of the deep carbonate rocks of the Tarim Basin have been estimated.

Experimental Investigation of Soapstone and Granite Rocks as Energy-Storage Materials for Concentrated Solar Power Generation and Solar Drying Technology

“…Other common TES materials shown in Table 3 have lower conductivity values than all the four experimental values As displayed in Figure 16, at lower temperatures the rate of decrease of thermal conductivity is higher in CS rocks than in the other three rocks but, at higher temperatures shown in Figure 17, its rate of decrease is the lowest compared to US, CG, and UG rocks. Chen et al 30 explained that the rate of decrease of thermal conductivities is dependent on the its values at room temperature, whereby conductivities between 2.5 and 3.5 W/(m•K) will show a linear decrease while those below 2.5 W/(m•K) will have a minor decrease at lower temperature and a significant decrease at higher temperatures. Thus, the soapstone sample CS showed significantly higher conductivity values at higher temperatures as compared to US, CG, and UG rocks.…”

“…The rock samples were dried in the oven at 100 °C for 5 h so as to remove both the absorbed and adsorbed water . The characterization experiments on the thermo-physical, thermo-chemical and thermo-mechanical properties as related to thermal energy storage were done as summarized in Figure .…”

“…A high temperature test was performed to observe the capacity of the rocks to resist fracture caused by increase in temperature up to higher temperatures . Samples of 10 × 10 × 10 mm 3 were enclosed in a CBFL518C Cole Palmer Box furnace and exposed to 700 and 1000 °C for 6 h so that the rock samples could reach a steady temperature field. , They were left to gradually cool in the furnace until they reached room temperature …”

“…The rock samples were dried in the oven at 100 °C for 5 h so as to remove both the absorbed and adsorbed water. 30 The characterization experiments on the thermo-physical, thermo-chemical and thermo-mechanical properties as related to thermal energy storage were done as summarized in Figure 2 . The characterization was done for low temperatures (<150 °C) to examine the solar drying applications potential and higher temperatures (>300 °C) to examine the concentrated solar power generation potential of the rock materials.…”

“…33 Samples of 10 × 10 × 10 mm 3 were enclosed in a CBFL518C Cole Palmer Box furnace and exposed to 700 and 1000 °C for 6 h so that the rock samples could reach a steady temperature field. 19,30 They were left to gradually cool in the furnace until they reached room temperature. 33 Thermo-physical Properties.…”