Two types of fidelity can be used in the current version of the Heat Transfer Library. There is a trade-off between the capability of the physical phenomena expression and the simulation cost. Thus, you need to specify it with your purpose of simulation.

If you use this mode, the properties is assigned with the following constants.

Specific heat capacity at the constant pressure $\mathrm{c\_\_p}$$\frac{J}{\mathrm{kg}\cdot K}$ :

$\mathrm{c\_\_p}\=1005.45$

Molar mass $\mathrm{MM} \frac{\mathrm{kg}}{\mathrm{mol}}$ :

$\mathrm{MM}\=0.028965116$

Gas constant $\mathrm{R\_\_gas} \frac{J}{\mathrm{kg}\cdot K}$ :

$\mathrm{R\_\_gas}\=\frac{R}{\mathrm{MM}}$

(*) $R$ is Universal gas constant, and the value is $8.3144598$$\frac{J}{\mathrm{mol}\cdot K}$

Specific heat capacity at the constant volume $\mathrm{c\_\_v}$$\frac{J}{\mathrm{kg}\cdot K}$ :

$\mathrm{c\_\_v}\=\mathrm{c\_\_p}-\mathrm{R\_\_gas}$

Dynamic viscosity $\mathrm{\μ} \mathrm{Pa} s$ :

$\mathrm{\μ}\=0.0000182$

Thermal conductivity $k \frac{W}{m\cdot K}$ :

$k\=0.026$

And, the specific enthalpy $\mathrm{hflow}$ is calculated with the following equation, and which is called as $\mathrm{Function\_\_hflow}$ :

$\mathrm{hflow}\=\mathrm{c\_\_p}\cdot T\+\mathrm{hflow\_\_off}$

$\mathrm{hflow\_\_off}\=124648.4919$

(*) The offset value of specific enthalpy is defined to be the same value as the other types of property at 273.15[K] and 101325[Pa]

If you use this mode, the properties is assigned with the following equations and constants.

Specific heat capacity at the constant pressure $\mathrm{c\_\_p}$$\frac{J}{\mathrm{kg}\cdot K}$,and which is called as $\mathrm{Function\_\_cp}$ :

$\mathrm{c\_\_p}\&equals;\mathrm{R\_\_gas}\cdot \left\{\begin{array}{cc}\frac{\mathrm{alow\_\_1}}{T^2}\&plus;\frac{\mathrm{alow\_\_2}}{T}\&plus;\mathrm{alow\_\_3}\&plus;\mathrm{alow\_\_4}\cdot T\&plus;\mathrm{alow\_\_5}\cdot T^2\&plus;\mathrm{alow\_\_6}\cdot T^3\&plus;\mathrm{alow\_\_7}\cdot T^4& T<1000\\ \frac{\mathrm{ahigh\_\_1}}{T^2}\&plus;\frac{\mathrm{ahigh\_\_2}}{T}\&plus;\mathrm{ahigh\_\_3}\&plus;\mathrm{ahigh\_\_4}\cdot T\&plus;\mathrm{ahigh\_\_5}\cdot T^2\&plus;\mathrm{ahigh\_\_6}\cdot T^3\&plus;\mathrm{ahigh\_\_7}\cdot T^4& \mathrm{others}\end{array}\right.$

(*) $\mathrm{alow\_\_1}..\mathrm{alow\_\_7}$ and $\mathrm{ahigh\_\_1}..\mathrm{ahigh\_\_7}$ are NASA Glenn coefficients[1]

Molar mass $\mathrm{MM} \frac{\mathrm{kg}}{\mathrm{mol}}$ :

$\mathrm{MM}\&equals;0.0289651159$

Gas constant $\mathrm{R\_\_gas} \frac{J}{\mathrm{kg}\cdot K}$ :

$\mathrm{R\_\_gas}\&equals;\frac{R}{\mathrm{MM}}$

(*) $R$ is Universal gas constant, and the value is $8.3144598$$\frac{J}{\mathrm{mol}\cdot K}$

Specific heat capacity at the constant volume $\mathrm{c\_\_v}$$\frac{J}{\mathrm{kg}\cdot K}$ :

$\mathrm{c\_\_v}\&equals;\mathrm{c\_\_p}-\mathrm{R\_\_gas}$

Dynamic viscosity $\mathrm{\&mu;} \mathrm{Pa} s$ (Fitted equation), and which is called as $\mathrm{Function\_\_vis}$ :

$\mathrm{\&mu;}\&equals;8.582645242{10}^{\mathrm{-6}}-\frac{0.0007885132499}{T}+4.616415634 {10}^{\mathrm{-8}}T-1.514928283{10}^{\mathrm{-11}}{T}^2+2.766144637{10}^{\mathrm{-15}}{T}^3$

Thermal conductivity $k \frac{W}{m\cdot K}$ (Fitted equation) as $\mathrm{Function\_\_k}$ :

$k\&equals;0.004919497129-\frac{0.568804205481540}{T}+0.00008519526051T-2.658073105{10}^{\mathrm{-8}}{T}^2+4.653561257{10}^{\mathrm{-12}}{T}^3$

And, the specific enthalpy $\mathrm{hflow} \frac{J}{\mathrm{kg}}$ is calculated with the following equation, and which is called as $\mathrm{Function\_\_hflow}$ :

$\mathrm{hflow}\&equals;\mathrm{R\_\_gas}\cdot \&lcub;\begin{array}{cc}\mathrm{blow\_\_1}-\frac{\mathrm{alow\_\_1}}{T}\&plus;\mathrm{alow\_\_2}\cdot \log \left(T\right)\&plus;\mathrm{alow\_\_3}\cdot T\&plus;\frac{1}{2}\cdot \mathrm{alow\_\_4}\cdot T^2\&plus;\frac{1}{3}\cdot \mathrm{alow\_\_5}\cdot T^3\&plus;\frac{1}{4}\cdot \mathrm{alow\_\_6}\cdot T^4\&plus;\frac{1}{5}\cdot \mathrm{alow\_\_7}\cdot T^5& T<1000\\ \mathrm{bhigh\_\_1}-\frac{\mathrm{ahigh\_\_1}}{T}\&plus;\mathrm{ahigh\_\_2}\cdot \log \left(T\right)\&plus;\mathrm{ahigh\_\_3}\cdot T\&plus;\frac{1}{2}\cdot \mathrm{high\_\_4}\cdot T^2\&plus;\frac{1}{3}\cdot \mathrm{ahigh\_\_5}\cdot T^3\&plus;\frac{1}{4}\cdot \mathrm{ahigh\_\_6}\cdot T^4\&plus;\frac{1}{5}\cdot \mathrm{ahigh\_\_7}\cdot T^5& \mathrm{others}\end{array}\&plus;\mathrm{hflow\_\_off}$

(*) $\mathrm{alow\_\_1}..\mathrm{alow\_\_7}$ and $\mathrm{ahigh\_\_1}..\mathrm{ahigh\_\_7}$ and $\mathrm{blow\_\_1}$ and $\mathrm{bhigh\_\_1}$ are NASA Glenn coefficients[1]

$\mathrm{hflow\_\_off}\&equals;428725.6773$

(*) The offset value of specific enthalpy is defined to be the same value as the other types of property at 273.15[K] and 101325[Pa]

You can simulate model with Air components in Static mass flow mode and Dynamic mass flow mode. There is a trade-off between the capability of the physical phenomena expression and the simulation cost. Thus, you need to specify it with your purpose of simulation.

The following model is one of the simplest Air simulation model. At both sides of edge, there are Air.Boundaries.AirBoundary components to define the boundary conditions. And, Air.Basic.AirVolume is placed at the center of the model, which is for Mass and Energy conservation calculation. The last pieces are Air.Basic.AirFlow which is placed at between AirBoundary and AirVolume. Pressure difference and Mass flow rate will be calculated in them.

With this model, the behavior of two mode is explained in below.

If you select Static mode, Mass flow rate will be defined with

$\mathrm{mflow1}\&equals;\mathrm{mflow0}$

Then, the pressure difference is calculated from

$\mathrm{dp}\&equals;\mathrm{Function}\left(\mathrm{mflow1}\right)$

(*) In this library, you can select several functions, like Linear type and Darcy-Weisbach equation.

Finally, p1 is obtained from

$\mathrm{p1}\&equals;\mathrm{p0}-\mathrm{dp}$

Thus, Mass flow rate is defined by the boundary condition. And by using Air.Basic.AirValve and FAN, you can control the value of it.

If you select Dynamic mode, the Mass flow rate condition $\mathrm{mflow0}$ is not used. In Air.Basic.AirVolume, Pressure will be calculated with Mass

and Energy conservation law. So, the pressure difference is obtained from

$\mathrm{dp}\&equals;\mathrm{p0}-\mathrm{p1}$

Mass flow rate is calculated from

$\mathrm{mflow1}\&equals;\mathrm{Function}\left(\mathrm{dp}\right)$

(*) In this library, you can select several functions, like Linear type and Darcy-Weisbach equation.

In this mode, the Mass flow rate is dynamically changed based on the pressure balance calculation.

[1] : McBride B.J., Zehe M.J., and Gordon S. (2002): NASA Glenn Coefficients for Calculating Thermodynamic Properties of Individual Species. NASA report TP-2002-211556