Groundwater flow and Ground Heat Exchangers
Date Issued
April 2017
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).
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).