This funtions interpolates the collision integral of a water vapour/ air mixture for the lennard-jones potentials of air and water vapour, which are the inputs of the function.
ε12 = √(εair εsteam)
Ω = f(kB T ⁄ ε12)
function CollisionIntegral input Modelica.Units.SI.Temperature T; output Real Omega_D; end CollisionIntegral;