A Numerical Approach to Assessing Thermally Interacting Multiple Boreholes with Variable Heating Strength

Abstract

The temperature response in the soil surrounding multiple boreholes is evaluated numerically. The assumption of constant heat flux along the borehole wall is examined by coupling the problem to the heat transfer problem inside the borehole and presenting a model with variable heat flux along the borehole length. A numerical finite volume method in a three dimensional meshed domain is used to model the conduction of heat in the soil surrounding the boreholes. In order to determine the heat flux boundary condition, the analytical quasi-three-dimensional solution to the heat transfer problem of the U-tube configuration inside the borehole [1] is used. This solution takes into account the variation in heating strength along the borehole length due to the temperature variation of the fluid running in the U-tube. Thus, critical depths at which thermal interaction occurs can be determined.