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 |
Calculation of Reynolds Number
Re = |v|ρD/μa 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 |
Type | Name | Default | Description |
---|---|---|---|
Velocity | v | Mean velocity of fluid flow [m/s] | |
Density | rho | Fluid density [kg/m3] | |
DynamicViscosity | mu | Dynamic (absolute) viscosity [Pa.s] | |
Length | D | Characteristic dimension (hydraulic diameter of pipes) [m] |
Type | Name | Description |
---|---|---|
ReynoldsNumber | Re | Reynolds number [1] |
function ReynoldsNumber "Return Reynolds number from v, rho, mu, D" input SI.Velocity v "Mean velocity of fluid flow"; input SI.Density rho "Fluid density"; input SI.DynamicViscosity mu "Dynamic (absolute) viscosity"; input SI.Length D "Characteristic dimension (hydraulic diameter of pipes)"; output SI.ReynoldsNumber Re "Reynolds number"; algorithm Re := abs(v)*rho*D/mu;end ReynoldsNumber;
Re = |m_flow|*diameter/A/μ with m_flow = v*ρ*ASee also Pipes.BaseClasses.CharacteristicNumbers.ReynoldsNumber.
Type | Name | Default | Description |
---|---|---|---|
MassFlowRate | m_flow | Mass flow rate [kg/s] | |
DynamicViscosity | mu | Dynamic viscosity [Pa.s] | |
Length | D | Characteristic dimension (hydraulic diameter of pipes or orifices) [m] | |
Area | A | Modelica.Constants.pi/4*D*D | Cross sectional area of fluid flow [m2] |
Type | Name | Description |
---|---|---|
ReynoldsNumber | Re | Reynolds number [1] |
function ReynoldsNumber_m_flow "Return Reynolds number from m_flow, mu, D, A" input SI.MassFlowRate m_flow "Mass flow rate"; input SI.DynamicViscosity mu "Dynamic viscosity"; input SI.Length D "Characteristic dimension (hydraulic diameter of pipes or orifices)"; input SI.Area A = Modelica.Constants.pi/4*D*D "Cross sectional area of fluid flow"; output SI.ReynoldsNumber Re "Reynolds number"; algorithm Re := abs(m_flow)*D/A/mu;end ReynoldsNumber_m_flow;
Nusselt number Nu = alpha*D/lambda
Type | Name | Default | Description |
---|---|---|---|
CoefficientOfHeatTransfer | alpha | Coefficient of heat transfer [W/(m2.K)] | |
Length | D | Characteristic dimension [m] | |
ThermalConductivity | lambda | Thermal conductivity [W/(m.K)] |
Type | Name | Description |
---|---|---|
NusseltNumber | Nu | Nusselt number [1] |
function NusseltNumber "Return Nusselt number" input SI.CoefficientOfHeatTransfer alpha "Coefficient of heat transfer"; input SI.Length D "Characteristic dimension"; input SI.ThermalConductivity lambda "Thermal conductivity"; output SI.NusseltNumber Nu "Nusselt number"; algorithm Nu := alpha*D/lambda;end NusseltNumber;