Groundwater flow and Ground Heat Exchangers

Abstract

The flow of groundwater in multiple ground layers can play a significant role on the cooling or heating of vertical heat columns and Ground Heat Exchangers (GHEs), and hence on the construction of the latter. The heat distribution over time is described by the general heat transfer equation based on the energy balance. Thus the three-dimensional conservation of the transient heat equation for an incompressible fluid is applied in COMSOL Multiphysics. Heat transfer in porous media, Darcy’s velocity and seepage velocity are introduced by taking typical values of hydraulic conductivity, along with average borehole surface temperatures on every ground layer. The model parameters are validated against experimental values and multiple boreholes are examined. Although the key for an overall capital cost reduction for a GHE is known to be the borehole length, the numerical results here indicate that using the groundwater available, construction of shallow GHE systems can be achieved with an increase of the coefficient of performance (COP).