Impact of boiling heat transfer on geothermal reservoir simulation using local thermal non-equilibrium model

Abstract

An accurate evaluation of the heat extraction potential of the resource is critical for successful geothermal energy exploitation. This work deals with numerical simulation of heat and mass transfer inside geothermal reservoirs. Based on the Local Thermal Non-Equilibrium (LTNE) model a formulation has been proposed for modeling a geothermal reservoir. Thermodynamic properties are given by the IAPWS-IF97 formulation and the governing equations discretized using the Finite Difference Method. For verification, the results are compared to those from the geothermal AD-GPRS and TOUGH2. The influence of Nusselt number and average pore diameter on the LTNE model is investigated to determine its applicability range. The results indicate that for Reynolds number greater than 1 the LTE and LTNE models are practically the same. Also, the traditional convection heat transfer coefficient is compared with the boiling heat transfer coefficient in terms of how they influence the fluid and rock heat transfer model. The boiling heat transfer phenomenon has been studied before in the nuclear and electric power industries, however, this is the first time that this phenomenon has been investigated in the geothermal context. The computed results show that the use of the boiling heat transfer model has a significant effect on the prediction of the amount of energy that can be extracted from the reservoir.