Avoid unit check warning in Dymola for IDEAS.Utilities.Psychrometrics.TWetBul_TDryBulPhi

[kldjonge]

In Dymola a unit inconsitency is trown (warning) for IBPSA.Utilities.Psychrometrics.TWetBul_TDryBulPhi and IBPSA.Utilities.Psychrometrics.TWetBul_TDryBulXi . The inconsitency is because of the empirical correlation that uses atan() this adds radians as the units. When the block is often used, the multiple warnings cloud the translation log which is somewhat anoying.

It can be fixed by adding a constant unitconv 1 with a unit="1/rad" such that the updated model becomes:

protected 
  constant Real unitconv(unit="1/rad")=1 "constant 1 with unit K to avoid unit warning";

    TWetBul      = 273.15 + TDryBul_degC
       * Modelica.Math.atan(0.151977 * sqrt(rh_per + 8.313659))*unitconv
       + Modelica.Math.atan(TDryBul_degC + rh_per)*unitconv
       - Modelica.Math.atan(rh_per-1.676331)*unitconv
       + 0.00391838 * rh_per^(1.5) * Modelica.Math.atan( 0.023101 * rh_per)*unitconv  - 4.686035;