Air Flow
Flow calculation of Air
Description
Equations
Variables
Connections
Parameters
See Also
The Air Flow component models a generic flow calculation for the lumped thermal fluid simulation of Air. In this component, pressure difference and mass flow rate are calculated.
The calculation is changed based on parameter values of Type of flow and Dynamics of mass in the Air Settings component.
Type of flow = Linear and Dynamics of mass = Static
Pressure difference is calculated with:
dp=1A⋅α__linear⋅mflow
Type of flow = Linear and Dynamics of mass = Dynamic
Mass flow rate is calculated with:
mflow=A⋅α__linear⋅dp
Type of flow = Square root and Dynamics of mass = Static
dp=1A⋅α__sqrt2⋅mflow2⋅signmflow
Type of flow = Square root and Dynamics of mass = Dynamic
In theory, Mass flow rate is calculated with:
mflow=A⋅α__sqrt⋅dp
In the Heat Transfer Library, the following equation is used to resolve difficulties of the numerical calculation:
mflow=A⋅α__sqrt⋅`HeatTransfer.Functions.regRoot`dp,sharpness
(*) `HeatTransfer.Functions.regRoot` is the same function as `Modelica.Fluid.Utilities.regRoot`. To check the details of the package and view the original documentation, which includes author and copyright information, click here.
Type of flow = Darcy-Weisbach and Dynamics of mass = Static
dp=12⋅λ⋅LD__h⋅A2⋅{inStream`port_a.rho`dp≥0inStream`port_b.rho`others⋅mflow2⋅signmflow
Type of flow = Darcy-Weisbach and Dynamics of mass = Dynamic
mflow=2⋅D__h⋅A2λ⋅L⋅{inStream`port_a.rho`dp≥0inStream`port_b.rho`others⋅dp
mflow=2⋅D__h⋅A2λ⋅L⋅`HeatTransfer.Functions.regRoot2`dp,dp_small,inStream`port_a.rho`,inStream`port_b.rho`,true,sharpness
(*) `HeatTransfer.Functions.regRoot2` is the same function as `Modelica.Fluid.Utilities.regRoot2`. To check the details of the package and view the original documentation, which includes author and copyright information, click here.
Common definitions are the following:
dp=`port_a.p`−`port_b.p`
v=mflow{inStream`port_a.rho`dp≥0inStream`port_b.rho`others⋅A
`port_a.mflow`=mflow
`port_b.mflow`=−mflow
`port_a.hflow`=inStream`port_b.hflow`
`port_b.hflow`=inStream`port_a.hflow`
`port_a.rho`=inStream`port_b.rho`
`port_b.rho`=inStream`port_a.rho`
`port_a.T`=inStream`port_b.T`
`port_b.T`=inStream`port_a.T`
Symbol
Units
Modelica ID
dp
Pa
Pressure difference
p
mflow
kgs
Mass flow rate
v
ms
Velocity of flow
Name
port__a
Air Port
port_a
port__b
port_b
Default
Airsimulationsettings
AirSettings1
−
Specify a component of Air simulation settings
Settings
Type offlow
Linear
Select Flow calculation type
- Linear
- Square root
- Darcy-Weisbach
TypeOfFlow
α__linear
10
Flow coefficient for Linear type
alpha_lin
α__sqrt
60
Flow coefficient for Square root type
alpha_sqrt
L
0.1
m
Pipe length (Only for Darcy-Weisbach)
D__h
Internal hydraulic diameter (Only for Darcy-Weisbach)
Dh
A
Pi400
m2
Flow area
λ
0.000015
Friction coefficient for Darcy-Weisbach equation
lambda
dp__small
Approximation of function for |dp| <= dp_small
dp_small
sharpness
1.0
Sharpness of approximation for sqrt(dp) and sqrt(rho * dp)
Heat Transfer Library Overview
Air Overview
Air Basic Overview
Download Help Document