Air Valve
Control the flow of Air
Description
Equations
Variables
Connections
Parameters
See Also
The Air Valve component models a generic valve which is to control the flow for the lumped thermal fluid simulation of Air. In this component, pressure difference and mass flow rate is calculated based mainly on valve opening.
The calculation is changed based on parameter values of Type of flow, Calculation Type, and Dynamics of mass in the Air Settings component.
Type of flow = Linear and Dynamics of mass = Static
Calculation Type = true
Pressure difference is calculated with:
dp=1A⋅α__linear⋅mflow
Mass flow rate is calculated with:
mflow=opening__act⋅`port_a.mflow`
`port_b.mflow`=−mflow
Calculation Type = false
dp=1A⋅opening__act⋅α__linear⋅mflow
mflow=`port_a.mflow`
Type of flow = Linear and Dynamics of mass = Dynamic
mflow=opening__act⋅A⋅α__linear⋅dp
`port_a.mflow`=mflow
Type of flow = Square root and Dynamics of mass = Static
dp=1A⋅α__sqrt2⋅mflow2⋅signmflow
dp=1A⋅opening__act⋅α__sqrt2⋅mflow2⋅signmflow
Type of flow = Square root and Dynamics of mass = Dynamic
In theory, Mass flow rate is calculated with:
mflow=opening__act⋅A⋅α__sqrt⋅dp
In the Heat Transfer Library, the following equation is used to resolve difficulties of the numerical calculation:
mflow=opening__act⋅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
dp=12⋅λ⋅LD__h⋅A⋅opening__act2⋅{inStream`port_a.rho`dp≥0inStream`port_b.rho`others⋅mflow2⋅signmflow
Type of flow = Darcy-Weisbach and Dynamics of mass = Dynamic
Mass flow rate is calculated with in theory:
mflow=2⋅D__h⋅opening__act⋅A2λ⋅L⋅{inStream`port_a.rho`dp≥0inStream`port_b.rho`others⋅dp
mflow=2⋅D__h⋅opening__act⋅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.
If Dynamic of mass = Static, valve opening is calculated with:
opening__act=min1.0,maxopening,1.0⋅10−10
On the other hand, if Dynamic of mass = Dynamic, it is calculated with:
ⅆopening__actⅆt=min1.0,maxopening,1.0⋅10−10−opening__actT__const
Common definitions are the following:
dp=`port_a.p`−`port_b.p`
v=mflow{inStream`port_a.rho`dp≥0inStream`port_b.rho`others⋅opening__act⋅A
`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
opening__act
−
Valve opening used for Flow calculation
opening_act
typeA_opening
Valve opening used if Calculation type = true and Dynamic of mass = Static (Internal calculation use only)
typeB_opening
Valve opening used if Calculation type = false and Dynamic of mass = Static (Internal calculation use only)
Name
port__a
Air Port
port_a
port__b
port_b
opening
Valve opening
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)
T__const
0.001
s
Time constant for Valve opening (Only if Dynamic of mass = Dynamic)
T_const
Calculation Type
true
If true, Mass flow rate is controlled by Valve opening directly. If false, the calculation of Mass flow rate is consistent with Dynamic of mass = Dynamic (Only if Dynamic of mass = Static)
CalType
Heat Transfer Library Overview
Air Overview
Air Basic Overview
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