Use of COMSOL as a Tool in the Design of an Inclined Multiple Borehole Heat Exchanger

E. Johansson[1], J. Acuña[1], B. Palm[1]
[1]Royal Institute of Technology KTH, Stockholm, Sweden

A field of connected boreholes can be used both for cooling, heating and storage purposes. The boreholes transfer heat to or from the ground, which over time changes the temperature in the ground. It is important that the borehole field is properly sized and evaluated before the construction. This study presents results from borehole field evaluations of inclined boreholes used for cooling purposes, modeled with the software COMSOL Multiphysics. The three dimensional problem is solved with transient heat transfer equations and the borehole surface temperature is obtained after several years of operation. Temperature distribution and flow directions illustrate the results. A correct borehole length and configuration that meets the temperature requirements can be determined.