Modelica.Fluid.Pipes.BaseClasses.CharacteristicNumbers

Functions to compute characteristic numbers

Information

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

Package Content

Name	Description
ReynoldsNumber	Return Reynolds number from v, rho, mu, D
ReynoldsNumber_m_flow	Return Reynolds number from m_flow, mu, D, A
NusseltNumber	Return Nusselt number

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 Type	Characteristic Dimension D	Velocity v
Circular Pipe	diameter	m_flow/ρ/crossArea
Rectangular Duct	4*crossArea/perimeter	m_flow/ρ/crossArea
Wide Duct	distance between narrow, parallel walls	m_flow/ρ/crossArea
Packed Bed	diameterOfSpericalParticles/(1-fluidFractionOfTotalVolume)	m_flow/ρ/crossArea (without particles)
Device with rotating agitator	diameterOfRotor	RotationalSpeed*diameterOfRotor

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

Inputs

Name Description

v Mean velocity of fluid flow [m/s]

rho Fluid density [kg/m3]

mu Dynamic (absolute) viscosity [Pa.s]

D Characteristic dimension (hydraulic diameter of pipes) [m]

Name	Description
v	Mean velocity of fluid flow [m/s]
rho	Fluid density [kg/m3]
mu	Dynamic (absolute) viscosity [Pa.s]
D	Characteristic dimension (hydraulic diameter of pipes) [m]

Outputs

Name Description

Re Reynolds number [1]

Name	Description
Re	Reynolds number [1]

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

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

Inputs

Name Description

m_flow Mass flow rate [kg/s]

mu Dynamic viscosity [Pa.s]

D Characteristic dimension (hydraulic diameter of pipes or orifices) [m]

A Cross sectional area of fluid flow [m2]

Name	Description
m_flow	Mass flow rate [kg/s]
mu	Dynamic viscosity [Pa.s]
D	Characteristic dimension (hydraulic diameter of pipes or orifices) [m]
A	Cross sectional area of fluid flow [m2]

Outputs

Name Description

Re Reynolds number [1]

Name	Description
Re	Reynolds number [1]

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

Name Description

alpha Coefficient of heat transfer [W/(m2.K)]

D Characteristic dimension [m]

lambda Thermal conductivity [W/(m.K)]

Name	Description
alpha	Coefficient of heat transfer [W/(m2.K)]
D	Characteristic dimension [m]
lambda	Thermal conductivity [W/(m.K)]

Outputs

Name Description

Nu Nusselt number [1]

Name	Description
Nu	Nusselt number [1]

Automatically generated Mon Sep 23 17:20:46 2013.