Model of a single U-tube borehole heat exchanger.
The borehole heat exchanger is vertically discretized into
nseg elements of height
h=hBor⁄nseg.
Each segment contains a model for the heat transfer in the borehole,
with a uniform borehole wall boundary temperature given by the
port_wall
port.
The heat transfer in the borehole is computed using a convective heat transfer coefficient that depends on the fluid velocity, a heat resistance between the two pipes, and a heat resistance between the pipes and the borehole wall. The heat capacity of the fluid and the heat capacity of the grout are taken into account. The vertical heat flow is assumed to be zero.