FEFLOW - A new efficient modelling procedure for ground heat exchanger arrays

Previously, borehole heat exchangers in FEFLOW were either simulated in a fully-discretised way, leading to very detailed, but huge models, or only considering the net heat abstraction/injection via boundary conditions. While in the first case the simulation of larger arrays of heat exchangers is not feasible due to model complexity and prohibitive computation times, the latter option might for example be oversimplifying the short-term processes when heat exchangers are run with changing input temperatures. With the new heat exchanger simulation option, heat transport in borehole heat exchangers can be simulated by a special 1-D element, calculating the heat transport in the pipes (u-shape, double-u-shape, or coaxial) and the transfer of heat via the grout into the surrounding subsurface environment.

The new feature extends FEFLOW’s boundary conditions for heat pipes and is undertaken through the new BHE dialogue.

FEFLOW 5.4 - new graphical and scientific features and improvements:

• Borehole heat exchanger simulation
• Anisotropy of the heat conductivity
• SAMG as standard solver
• Spline interpolation for parametric relationships in unsaturated flow
• Parameter zones in FEFLOW Explorer
• Elemental reference distribution for porosity values used for isochrone calculation
• Output (simulation) times in different units
• Pressure is available as a variable in the viscosity editor
• Improved parallelisation
• Graphic-less batch mode
• Alternative search algorithm with spatial indexing
• New IFM functions

ESI is a leading specialist consultancy providing modelling services, technologies, training and support for ground source heating and cooling system design and troubleshooting, and is appointed reseller and support centre for FEFLOW and other codes developed by DHI-WASY.

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