modelRayleighNumber
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Information
This model calculates the rayleigh number for a given fluid and characteristic length. It is calculated using Eq 9.25 in Incropera and DeWitt (1996). The equation is:
RaL = GrL Pr (g B (TS - TF) L3) /(ν*α)
where:
RaL is the Rayleigh number, GrL is the Grashof number, Pr
is the Prandtl number, g is gravity, B is the isobaric expansion coefficient,
TS is the temperature of the surface, TF is the temperature of the
fluid, L is the characteristic length, ν is the kinematic viscosity and α
is the thermal diffusivity.
This model is currently only used in natural convection calculations for water. As a result, the calculations reference functions to identify properties of water instead of a medium model.
References
Fundamentals of Heat and Mass Transfer (Fourth Edition), Frank Incropera and David DeWitt, John Wiley and Sons, 1996
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Diameter | ChaLen | Characteristic length |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Interfaces.RealInput | TSur | Surface temperature of the HX | |
| Modelica.Blocks.Interfaces.RealOutput | Ra | Rayleigh number | |
| Modelica.Blocks.Interfaces.RealOutput | Pr | Prandlt number | |
| Modelica.Blocks.Interfaces.RealInput | TFlu | Temperature of the surrounding fluid |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Real | Gr | Grashof number | |
| Real | B | isobaricExpansionCoefficient | |
| Real | nu | Kinematic viscosity of the medium | |
| Modelica.Units.SI.DynamicViscosity | mu | Dynamic viscosity of the medium | |
| Modelica.Units.SI.Density | rho | Density of the medium |
Contents
| Name | Description |
|---|---|
 Medium | Fluid medium model |
Revisions
-
February 26, 2013 by Peter Grant
First implementation