This information is part of the Modelica Standard Library maintained by the Modelica Association.

This function provides two similar methods for estimating the thermal conductivity of polyatomic gases. The Eucken method (input method == 1) gives good results for low temperatures, but it tends to give an underestimated value of the thermal conductivity (lambda) at higher temperatures.
The Modified Eucken method (input method == 2) gives good results for high-temperatures, but it tends to give an overestimated value of the thermal conductivity (lambda) at low temperatures.

lambda = thermalConductivityEstimate(Cp, eta, method, data)

Cp	Type: SpecificHeatCapacity (J/(kg⋅K)) Description: Constant pressure heat capacity
eta	Type: DynamicViscosity (Pa⋅s) Description: Dynamic viscosity
method	Default Value: 1 Type: Integer Description: 1: Eucken Method, 2: Modified Eucken Method
data	Type: DataRecord Description: Ideal gas data

lambda	Type: ThermalConductivity (W/(m⋅K)) Description: Thermal conductivity [W/(m.k)]