This function is based on based on NASA CEA [McBride1996, Svehla1995]
Although specific volume is an input to this function, the result is independent of specific volume.
function theta
extends Modelica.Icons.Function;
input Q.TemperatureAbsolute T = 298.15*U.K "Temperature" annotation(
Dialog(__Dymola_label = "<html><i>T</i></html>"));
input Q.VolumeSpecific v = 298.15*U.K/U.atm "Specific volume";
output Q.ResistivityThermal theta "Thermal resistivity" annotation(
Dialog(__Dymola_label = "<html>θ</html>"));
end theta;