This model evaluates the complex coefficient matrix F_mk from Claesson and Hellstrom (2011).
J. Claesson and G. Hellstrom. Multipole method to calculate borehole thermal resistances in a borehole heat exchanger. HVAC&R Research, 17(6): 895-911, 2011.
function multipoleFmk extends Modelica.Icons.Function; input Integer nPip "Number of pipes"; input Integer J "Number of multipoles"; input Real QPip_flow[nPip](each unit = "W/m") "Heat flow in pipes"; input Real PRea[nPip, J] "Multipoles (Real part)"; input Real PIma[nPip, J] "Multipoles (Imaginary part)"; input Modelica.Units.SI.Radius rBor "Borehole radius"; input Modelica.Units.SI.Radius rPip[nPip] "Outter radius of pipes"; input Modelica.Units.SI.Position xPip[nPip] "x-Coordinates of pipes"; input Modelica.Units.SI.Position yPip[nPip] "y-Coordinates of pipes"; input Modelica.Units.SI.ThermalConductivity kFil "Thermal conductivity of grouting material"; input Modelica.Units.SI.ThermalConductivity kSoi "Thermal conductivity of soil material"; output Real FRea[nPip, J] "Multipole coefficients"; output Real FIma[nPip, J] "Multipole coefficients"; end multipoleFmk;