Axial Fan

Fans cool electronic devices by drawing cool air over the components' heat sinks. In axial fans, the gas flow is parallel to the fan's axis. They generally produce low pressures with high flow rates.

The Electronics Cooling Toolset supports an Axial Fan QuickPart that consists of a fan hub, a housing, and a fan volume. The fan volume represents the volume swept out by the fan blades and does not consider the individual blades of the fan.

The geometry of most axial fans can be simplified to follow the available templated fan type:


Templated

If the built-in axial fan is not suitable, you can define a Custom axial fan whose geometry is based on Construction Geometries that you specify.

An Axial Fan QuickPart imposes a pressure jump upon the flow that passes through the fan volume. The pressure rise depends on the fan performance curve that you specify. A fan performance curve describes the pressure rise across the fan—that is the static pressure measured downstream of the fan minus the total pressure that is measured upstream of the fan—as a function of the volumetric flow rate.

An optional fan hub heat source allows you to model the heat that is generated by the electric motor of the fan.

Note	The material of the fan volume is the Default Gas material that you specify in the Setup panel. Axial Fan QuickParts are currently not supported for liquid domains.

Axial Fan—Properties

The following properties are common to Templated and Custom axial fans:

Name

Specifies the name of the heat sink under which it is stored in the tree.

Geometry

Local Origin

Specifies the position of the axial fan's local coordinate system. See X_or, Y_or, Z_or in the Graphics window. It is used for placing the fan in the simulation domain. The following options are available:

A: Center of front (Zmax) face.
B: Center of the fan geometry.
C: Center of back (Zmin) face.
Custom: This value appears when you set the local origin interactively within the Graphics window, see Placing Object Interactively.

Note	For a Custom axial fan, the local origin of the geometry is placed in the origin of the Laboratory coordinate system, by default.

Placement

See Placement properties.

Physics

Housing Material, Hub Material

Specify the material of the fan's housing and hub, respectively. You can choose the materials from the list of Solid Sim Materials that you define in the Setup panel.

Hub Heat Source

Specifies the total heat generated by the electric motor that is integrated in the fan hub.

Fan Surface

Controls if the pressure jump is imposed on the Front Surface or on the Back Surface of the fan volume. To check the respective surface, see the origin of the black arrow within the Graphics window.

Reverse Direction

Allows you to reverse the direction of the fan flow to show from the specified Fan Surface into the fan volume. To check the flow direction, see the black arrow within the Graphics window.

Fan Curve Type

Controls the specification of the fan performance curve. The following options are available:

Linear:
Defines the fan curve as a linear function. The pressure rise across the Fan Surface is calculated as

$p (\dot{v}) = - \frac{p_{\max}}{{\dot{v}}_{\max}} \dot{v} + p_{\max}$
where $p_{\max}$ and ${\dot{v}}_{\max}$ are the specified Maximum Pressure and Maximum Flow, respectively. The Data Rotation Rate property specifies the speed at which the fan data was collected. The Operating Rotation Rate property specifies the speed at which you want the fan to run. For more information, see Scaling the Fan Performance Curve.
Table:
Defines the fan curve as a table of pressure rise versus volumetric flow rate as indicated by the imported Fan Curve File (*.csv). After the import, select the appropriate Pressure Units and Volume Flow Units. The pressure rise is calculated by linear interpolation between the data points in the table. Outside the intervals, the nearest limit is used.

A fan performance curve provides the pressure rise across the fan for a specific fluid temperature and fan rotation rate.

If your data correspond to some standard temperature, you must manually modify the fan performance curve to suit the temperature in your simulation using established fan laws:

Δ P_{2} = Δ P_{1} (T_{1} / T_{2})

If your data correspond to some standard fan rotation rate, the Electronics Cooling Toolset automatically adjusts the fan performance curve to suit the fan rotation rate in your simulation:

Δ P_{2} = Δ P_{1} {(ω_{2} / ω_{1})}^{2}

ψ_{2} = ψ_{1} (ω_{2} / ω_{1})

where:

$ω_{1}$ is the specified Data Rotation Rate, that is the fan rotation rate at which the fan performance curve was measured.
$ω_{2}$ is the specified Operating Rotation Rate, that is the fan rotation rate in your simulation.
$Δ P_{1}$ and $Δ P_{2}$ are the measured pressure rise and the pressure rise in your simulation, respectively.
$ψ_{1}$ and $ψ_{2}$ are the measured volumetric flow rate and the volumetric flow rate in your simulation, respectively.

The following geometry properties characterize the different types of axial fans:

Templated—Specific Properties


Geometry	Housing Width Specifies the extent of the housing in x- and y-direction, in the axial fan's local coordinate system. See X_or, Y_or, Z_or in the Graphics window. Housing Depth Specifies the length that the housing extends from back to front. Fan Radius Specifies the outer radius of the fan volume. Hub Radius Specifies the radius of the fan hub.

Custom—Specific Properties


Geometry	Selected Housing, Selected Fluid, Selected Hub Specify the Construction Geometries that describe the housing, the fan volume and the fan hub, respectively. Select Front Faces, Select Back faces Specify the front surface and the back surface of the Selected Fluid, respectively, that are required for the Fan Surface specification.