GetMoistAirEnthalpy Function

  function GetMoistAirEnthalpy(TDryBulb, HumRatio) result(MoistAirEnthalpy)
    !+ Return moist air enthalpy given dry-bulb temperature and humidity ratio.
    !+ Reference:
    !+ ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 30

    real, intent(in)  ::  TDryBulb
      !+ Dry-bulb temperature in °F [IP] or °C [SI]
    real, intent(in)  ::  HumRatio
      !+ Humidity ratio in lb_H₂O lb_Air⁻¹ [IP] or kg_H₂O kg_Air⁻¹ [SI]
    real              ::  MoistAirEnthalpy
      !+ Moist air enthalpy in Btu lb⁻¹ [IP] or J kg⁻¹
    real              ::  BoundedHumRatio
      !+ Humidity ratio bounded to MIN_HUM_RATIO

    if (HumRatio < 0.0) then
      error stop "Error: humidity ratio is negative"
    end if
    BoundedHumRatio = max(HumRatio, MIN_HUM_RATIO)

    if (isIP()) then
        MoistAirEnthalpy = 0.240 * TDryBulb + BoundedHumRatio * (1061.0 + 0.444 * TDryBulb)
    else
        MoistAirEnthalpy = (1.006 * TDryBulb + BoundedHumRatio * (2501.0 + 1.86 * TDryBulb)) * 1000.0
    end if
  end function GetMoistAirEnthalpy