Convection Mechanisms For Geothermal Heat Exchangers In A Vertical Mine Shaft

Montana Tech is located in the historic mining town of Butte, MT and is adjacent to the Orphan Boy mine. This abandoned underground mine will be the heat source for a down-hole heat exchanger (DHE)/heat pump system. The mine was abandoned in the 1950?s and has since filled with water to within approximately 30 m of the surface. The shaft is composed of a 245 m vertical shaft connected with horizontal crosscut drifts at 60 m and 150 m below the water level that connect to a large stope with approximately 1250 million liters of water at a consistent 75-78°F temperature. The intent is to build this heating system to augment or fully heat a newly built 2,000 m2 building on the Montana Tech campus. As designed the system uses ?off-the-shelf? parts making the basic configuration straightforward with the exception of the DHE?s which need to be placed into the vertical shaft. Because there is little or no examples of placing the heat exchangers in a vertical shaft, the primary focus of this work was to model the heat exchanger placement and configuration in the vertical shaft such that thermal currents develop between the stope and vertical shaft in, via the horizontal crosscut drifts, in order to move the water and thereby provide the required energy. This study includes the modeling of water flow, temperature profiles, and the heat contribution from the surrounding rock walls.