Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers

Functions to compute characteristic numbers

Information

Extends from Modelica.Icons.Package (Icon for standard packages).

Package Content

Name Description
Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber ReynoldsNumber Return Reynolds number from v, rho, mu, D
Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber_m_flow ReynoldsNumber_m_flow Return Reynolds number from m_flow, mu, D, A
Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.NusseltNumber NusseltNumber Return Nusselt number

Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber

Return Reynolds number from v, rho, mu, D

Information

Calculation of Reynolds Number

Re = |v|ρD/μ

a measure of the relationship between inertial forces (vρ) and viscous forces (D/μ).

The following table gives examples for the characteristic dimension D and the velocity v for different fluid flow devices:

Device TypeCharacteristic Dimension DVelocity v
Circular Pipediameter m_flow/ρ/crossArea
Rectangular Duct4*crossArea/perimeter m_flow/ρ/crossArea
Wide Ductdistance between narrow, parallel walls m_flow/ρ/crossArea
Packed BeddiameterOfSpericalParticles/(1-fluidFractionOfTotalVolume) m_flow/ρ/crossArea (without particles)
Device with rotating agitatordiameterOfRotor RotationalSpeed*diameterOfRotor

Extends from Modelica.Icons.Function (Icon for functions).

Inputs

NameDescription
vMean velocity of fluid flow [m/s]
rhoFluid density [kg/m3]
muDynamic (absolute) viscosity [Pa.s]
DCharacteristic dimension (hydraulic diameter of pipes) [m]

Outputs

NameDescription
ReReynolds number [1]

Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber_m_flow Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber_m_flow

Return Reynolds number from m_flow, mu, D, A

Information

Simplified calculation of Reynolds Number for flow through pipes or orifices; using the mass flow rate m_flow instead of the velocity v to express inertial forces.
  Re = |m_flow|*diameter/A/μ
with
  m_flow = v*ρ*A
See also Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber.

Extends from Modelica.Icons.Function (Icon for functions).

Inputs

NameDescription
m_flowMass flow rate [kg/s]
muDynamic viscosity [Pa.s]
DCharacteristic dimension (hydraulic diameter of pipes or orifices) [m]
ACross sectional area of fluid flow [m2]

Outputs

NameDescription
ReReynolds number [1]

Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.NusseltNumber Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers.NusseltNumber

Return Nusselt number

Information

Nusselt number Nu = alpha*D/lambda

Extends from Modelica.Icons.Function (Icon for functions).

Inputs

NameDescription
alphaCoefficient of heat transfer [W/(m2.K)]
DCharacteristic dimension [m]
lambdaThermal conductivity [W/(m.K)]

Outputs

NameDescription
NuNusselt number [1]
Automatically generated Thu Oct 1 16:07:57 2020.