Air Settings - MapleSim Help

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Air Settings

Simulation settings for Air

Description

By placing the Air Settings component, you can define the simulation settings for Air. All components in the Air component library have an Air simulation settings parameter. You need to specify which Air Settings component is assigned with the parameter by name.

For example, if you place this Air Settings in the model workspace, the name AirSettings1 is assigned to it as default. Then, after placing Air.Basic.AirVolume, you need to check the value of Air simulation settings. As default, the value is AirSettings1, so the simulation settings is defined by AirSettings1. To change the associated Air Setting component, specify it by name.

This framework allows you to define and change the simulation settings for multiple components simultaneously.

Fidelity of properties

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.

 • Constant

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

Specific heat capacity at the constant pressure $\mathrm{c__p}$ :

$\mathrm{c__p}=1005.45$

Molar mass  :

$\mathrm{MM}=0.028965116$

Gas constant  :

$\mathrm{R__gas}=\frac{R}{\mathrm{MM}}$

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

Specific heat capacity at the constant volume $\mathrm{c__v}$ :

$\mathrm{c__v}=\mathrm{c__p}-\mathrm{R__gas}$

Dynamic viscosity  :

$\mathrm{μ}=0.0000182$

Thermal conductivity  :

$k=0.026$

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]

 • Ideal Gas (NASA Polynomial)

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

Specific heat capacity at the constant pressure $\mathrm{c__p}$,and which is called as $\mathrm{Function__cp}$ :

$\mathrm{c__p}=\mathrm{R__gas}\cdot \left\{\begin{array}{cc}\frac{\mathrm{alow__1}}{{T}^{2}}+\frac{\mathrm{alow__2}}{T}+\mathrm{alow__3}+\mathrm{alow__4}\cdot T+\mathrm{alow__5}\cdot {T}^{2}+\mathrm{alow__6}\cdot {T}^{3}+\mathrm{alow__7}\cdot {T}^{4}& T<1000\\ \frac{\mathrm{ahigh__1}}{{T}^{2}}+\frac{\mathrm{ahigh__2}}{T}+\mathrm{ahigh__3}+\mathrm{ahigh__4}\cdot T+\mathrm{ahigh__5}\cdot {T}^{2}+\mathrm{ahigh__6}\cdot {T}^{3}+\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  :

$\mathrm{MM}=0.0289651159$

Gas constant  :

$\mathrm{R__gas}=\frac{R}{\mathrm{MM}}$

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

Specific heat capacity at the constant volume $\mathrm{c__v}$ :

$\mathrm{c__v}=\mathrm{c__p}-\mathrm{R__gas}$

Dynamic viscosity  (Fitted equation), and which is called as $\mathrm{Function__vis}$ :

Thermal conductivity  (Fitted equation) as $\mathrm{Function__k}$ :

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

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

$\mathrm{hflow}=\mathrm{R__gas}\cdot {\begin{array}{cc}\mathrm{blow__1}-\frac{\mathrm{alow__1}}{T}+\mathrm{alow__2}\cdot \mathrm{log}\left(T\right)+\mathrm{alow__3}\cdot T+\frac{1}{2}\cdot \mathrm{alow__4}\cdot {T}^{2}+\frac{1}{3}\cdot \mathrm{alow__5}\cdot {T}^{3}+\frac{1}{4}\cdot \mathrm{alow__6}\cdot {T}^{4}+\frac{1}{5}\cdot \mathrm{alow__7}\cdot {T}^{5}& T<1000\\ \mathrm{bhigh__1}-\frac{\mathrm{ahigh__1}}{T}+\mathrm{ahigh__2}\cdot \mathrm{log}\left(T\right)+\mathrm{ahigh__3}\cdot T+\frac{1}{2}\cdot \mathrm{high__4}\cdot {T}^{2}+\frac{1}{3}\cdot \mathrm{ahigh__5}\cdot {T}^{3}+\frac{1}{4}\cdot \mathrm{ahigh__6}\cdot {T}^{4}+\frac{1}{5}\cdot \mathrm{ahigh__7}\cdot {T}^{5}& \mathrm{others}\end{array}+\mathrm{hflow__off}$

(*) $\mathrm{alow__1}..\mathrm{alow__7}$ and $\mathrm{ahigh__1}..\mathrm{ahigh__7}$ and $\mathrm{blow__1}$ and $\mathrm{bhigh__1}$ are NASA Glenn coefficients[1]

$\mathrm{hflow__off}=428725.6773$

(*) 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]

Dynamics of mass

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.

 • Static mode

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

$\mathrm{mflow1}=\mathrm{mflow0}$

Then, the pressure difference is calculated from

$\mathrm{dp}=\mathrm{Function}\left(\mathrm{mflow1}\right)$

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

Finally, p1 is obtained from

$\mathrm{p1}=\mathrm{p0}-\mathrm{dp}$

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.

 • Dynamic mode

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

$\mathrm{dp}=\mathrm{p0}-\mathrm{p1}$

Mass flow rate is calculated from

$\mathrm{mflow1}=\mathrm{Function}\left(\mathrm{dp}\right)$

(*) 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.

 References [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

Parameters

 Symbol Default Units Description Modelica ID $-$ Select Fidelity of properties   Constant :       Use constants for each properties   Ideal Gas (NASA Polynomial) :       Properties are calculated with Temperature-dependent       functions for Ideal gases, which are called as NASA       Polynomials Fidelity $\mathrm{Dynamic}$ $-$ Select Dynamics of Mass flow rate   Static :      Mass flow rate is static. Pressure drop are calculated at      at each elements of pressure losses   Dynamic :      Mass flow rate is calculated from pressure difference at      each elements of pressure losses Mass Dynamics

 See Also