Thermal conductivity of rocks and geothermal water

Abstract

In this article, the possibilities of use of geothermal energy in relation to the geothermal gradient and aquifer yield are described. Calculations represent information on potential geothermal water reserves that are not affected by cold return water inflow from the reinjection well after a certain period of production time. The calculations apply for continuous production of geothermal water from the aquifer without significant pumping breaks. where E = amount of heat passing through a particular area A (in J); H = strata thickness (in m); A = particular area through which the heat flux is passing (in m 2 ); T 2 -T 1 = temperature difference between strata borders (in K); τ = heat flux passing time (in s).For North-East (NE) Slovenia, we can write down the thermal conductivity in terms of rock density: Specific heat cSpecific heat is a physical quantity that describes the thermal property of the substance and defines how much energy is needed to increase the temperature of 1 kg mass for 1K, at constant pressure. For the rocks, the average value is c m = 835 (± 15%) J/kg · K; and for water, the value is c w = 4187 J/kg K. The calculation of specific heat of the rock in terms of porosity and at water density 1000 kg/m 3 and average rock density 2720 kg/m 3 is done as follows:where F = porosity.Specific heat of the rocks in NE Slovenia is c k = 0.602·e -1.177·H + 0.898. Volume-specific heat capacity (cρ)This parameter describes a product of specific heat and density and is defined as the amount of energy needed to raise the temperature of 1 m 3 of substance by 1 K at constant pressure.(cρ) L = (cρ) f · F + (cρ) m · (1 -F) (in J/m 3 · K) (5)Volume-specific heat capacity is a direct parameter used for the assessment and calculation of