HeatTransfer/Air/Basic/AirOrificeISO6358 - MapleSim Help
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Air Orifice ISO6358

Orifice of Air based on the standard ISO6358 which is for compressible flow

  

 

Description

Equations

Variables

Connections

Parameters

See Also

Description

The Air Orifice ISO6358 component models an orifice with flow-rate characteristics defined in standard ISO6358. This component calculates mainly pressure difference and mass flow rate.

Equations

In the ISO6358, the following equation is defined to calculate mass flow rate mflow.

mflow=p__aCρ__0T__0T__a1p__bp__ab__cr1b__cr2p__bp__a>b__crp__aCρ__0T__0T__aotherwise

Where mflow : mass flow rate [kg/s], p__a : upstream pressure [Pa], C : Sonic conductance [m3/s/Pa], ρ__0 : density of air at reference condition [kg/m3], T__0 : temperature of air at reference condition [K], T__a : upstream temperature [K], p__b : downstream pressure [Pa], and b__cr : critical pressure ratio [-].

 

The equation is modified for this component based on the reference book[1], and in order to have bi-directional flow.

mflow&equals;p__aC__act&rho;__0T__0T__ap__bp__a<b__cr_actp__aC__act&rho;__0T__0T__a1p__bp__ab__cr_act1b__cr_act2p__bp__a<b__lamk__abp__a&lpar;1p__bp__a&rpar;T__0T__ap__bp__a<1k__abp__b&lpar;1p__ap__b&rpar;T__0T__bp__bp__a<b__lam1p__bC__act&rho;__0T__0T__b1p__ap__bb__cr_act1b__cr_act2p__bp__a<b__cr_act1p__bC__act&rho;__0T__0T__botherwise

And, 

k__ab&equals;1000 C__act&rho;__010.999b__cr_act1b__cr_act2

Where mflow : mass flow rate [kg/s], p__a : upstream pressure [Pa], C__act : Sonic conductance [m3/s/Pa], &rho;__0 : density of air at reference condition [kg/m3], T__0 : temperature of air at reference condition [K], T__a : upstream temperature [K], p__b : downstream pressure [Pa], T__b : downstream temperature [K], b__cr_act : critical pressure ratio [-], and b__lam : pressure ratio at the boundary of laminar/turbulent [-]

 

(*) the above equation is used for both Dynamics of mass = Dynamic and Static.

 

Based on the parameter type, Sonic conductance C__act and Critical pressure ratio b__cr_act are obtained as follow.

Parameter Type = Sonic conductance

Sonic conductance

C__act&equals; C

Critical pressure ratio

b__cr_act&equals;b__cr

Parameter Type = Effective area

Sonic conductance

C__act&equals; S5

Critical pressure ratio

b__cr_act&equals;0.5

Parameter Type = Flow area of restriction

Sonic conductance

C__act&equals; 0.512A__rPi

Critical pressure ratio

b__cr_act&equals;b__cr

 

Definitions related to Mass flow rate and pressure:

dp&equals;`port_a.p``port_b.p`

pratio&equals;`port_b.p``port_a.p`

v&equals;mflow&lcub;inStream`port_a.rho`dp0inStream`port_b.rho`othersA__act

`port_a.mflow`&equals;mflow

`port_b.mflow`&equals;mflow

Specific enthalpy is defined with:

`port_a.hflow`&equals;inStream`port_b.hflow`

`port_b.hflow`&equals;inStream`port_a.hflow`

If Fidelity of properties = Constant, density is calculated with:

&rho;__0&equals;p__0`HeatTransfer.Properties.Fluid.SimpleAir.R_gas`T__0

(*) Regarding the value of properties for Constant, see more in Air Settings.

If Fidelity of properties = Ideal Gas (NASA Polynomial), Density is calculated with:

&rho;__0&equals;p__0`HeatTransfer.Properties.Fluid.NASAPolyAir.R_gas&sdot;T__0

(*) The properties are defined with NASA polynomials and coefficients, see more in Air Settings.

Port's variables are defined with:

`port_a.rho`&equals;inStream`port_b.rho`

`port_b.rho`&equals;inStream`port_a.rho`

`port_a.T`&equals;inStream`port_b.T`

`port_b.T`&equals;inStream`port_a.T`

References

[1] : Peter Beater (2006), "Pneumatic Drives - System Design, Modeling and Control", Springer

 

Variables

Symbol

Units

Description

Modelica ID

dp

Pa

Pressure difference

dp

pratio

Pressure ratio

pratio

mflow

kgs

Mass flow rate

mflow

v

ms

Velocity of flow

v

C__act

m3sPa

Actual Sonic conductance

C_act

b__cr_act

Actual critical pressure ratio

b_cr_act

k__ab

Linear gain for Laminar flow

k_ab

&rho;__0

kgm3

Density of air at reference condition

rho0

Connections

Name

Units

Condition

Description

Modelica ID

port__a

 

Air Port

port_a

port__b

 

Air Port

port_b

Parameters

Symbol

Default

Units

Description

Modelica ID

Airsimulationsettings 

AirSettings1

Specify a component of Air simulation settings

Settings

Parameter Type

General

Select parameter type

 - Sonic conductance

 - Effective area

 - Flow area of restriction

TypeOfParam

A

0.052Pi

m2

Flow area, only for monitoring flow velocity

A

C

1e−7

m3sPa

Sonic conductance

C

A__r

1e−5

m2

Flow area of the local restriction

Ar

b__cr

0.5

Critical pressure ratio

b_cr

S

5e−7

m2

Effective area

S

b__lam

0.999

Pressure ratio at the boundary of laminar/turbulent [-]

b_lam

p__0

100000

Pa

Reference pressure

p0

T__0

293.15

K

Reference temperature

T0

See Also

Heat Transfer Library Overview

Air Overview

Air Basic Overview