Development of Apparatus to Determine the Thermal Conductivity and Heat Transfer Modelling of Different Rocks

Abstract

Thermal conductivity is the property of material to conduct heat. Hence in mining industry, to deal with all kinds of rocks and minerals, the study of this property becomes essential. In deep underground mining, the temperature of strata increases as we go deeper into the earth which makes the working conditions very tough and harsh. Hence an effective ventilation arrangement is necessary, thermal conductivity is one of the major factors influencing the strata temperature. Hence, an attempt was made to understand the heat transfer mechanisms of different rocks.
The principle of the thermal conductivity apparatus is of a comparative nature in which the unknown thermal conductivity sample is sandwiched between two known thermal conductive materials. Heat is applied at one end which acts as a heat source and the other as heat sink. Temperatures are noted at different locations with the help of thermocouples. These temperature data are used to calculate the thermal conductivity of the desired substance.
For testing and analysis, different types of rocks were collected viz. coal, shale, sandstone was stacked together as well as individually to see their collective behavior and also their samples of varying lengths were taken to study its effect on the heat flow.
Two cases were studied in this dissertation. In the first case, samples were without any insulation and in the second case; the samples were insulated to study the behavior of heat flow trends with the help of heat transfer models using ANSYS 15.0. The measured value of temperature was used to calculate the thermal conductivity and compared with the actual thermal conductivity of the rocks to validate the apparatus. Hence, it can be concluded that in case of improper dissipation of heat, the rocks are more prone to self-heating and may lead to uncomfortable condition for miners in deep underground mines. Hence, it is necessary to dissipate the heat effectively for better working conditions for miners in underground mines Thermal conductivity being a thermo-physical specific property does not vary and the error between the calculated thermal conductivity and actual thermal conductivity is within the permissible range. The value of thermal conductivity for Coal, Shale, Sandstone are 0.226, 1.41, and 1.513 Wm-1K -1 respectively. Hence validating the apparatus.
Also the heat transfer models gave us an insight into how the heat propagates within rocks and showed the temperature profiles achieved in insulated as well as uninsulated cases.