Summary for: VolumeConnection < ThermalNetworkConnection

Class summary

VolumeConnection Connection between heat generation and external nodes.

The VolumeConnection class establishes a connection between volumetric heat generation and external ThermalNodes. It is mainly intended for modelling out-of-plane heat flux of 2D problems. See the initialize method documentation for some discussion on the mathematics.

The connection automatically scales the heat fluxes per model length, i.e. an external node with 1000 W of losses connected to a thermal model of 0.5 m effective length results in an apparent 2000 W/m volumetric heat source in the FEA model (in the absence of other heat sources/sinks).

A VolumeConnection must be constructed manually, by first creating the object, creating the associated thermal nodes and adding them to the thermal model, and setting all the required properties, for example: ´ambient = AmbientNode();´ ´ave_node = ThermalNode(‘average’);´ ´model.add_node(ambient, ave_node);´ ´conn = VolumeConnection();´ ´conn.volume_average_node = ave_node;´ ´conn.actual_node = ambient;´ ´conn.out_of_volume_bulk_thermal_conductivity = 10;´ ´conn.volume_height = 1;´ ´conn.elements = array_of_indices;´ ´conn.initialize;´ which models axial heat flux into an ambient temperature of default value of the AmbientNode class.

Properties

.actual_node The actual that is connected to the FE-problem.

.correction_coefficient Correction for out of vol conductivity.

.elements Indices to the finite elements in this connection.

.has_node2FEA Does this define a node-to-FEA connection.

Help for VolumeConnection/has_node2FEA is inherited from superclass ThermalNetworkConnection

.has_node2node Does this define a node-to-node connection.

Help for VolumeConnection/has_node2node is inherited from superclass ThermalNetworkConnection

.VolumeConnection/matrices is a property.

.out_of_volume_bulk_thermal_conductivity Thermal conductivity in

the out-of-plane direction.

.two_sided Is the connection two-sided?

Consider a cooling problem with an effective length of 1 meters, centered at z = 0. A ‘one-sided’ connection would mean that the problem domain is only cooled from the positive side, while a two-sided connection means we have heat flux also towards the negative side. A two-sided connection is assumed to be ** four (4) times more efficient, as the length of the cooling path is halved ** and each half of the cooling path only needs to carry half of the heat flux compared to the single-sided case.

.volume_average_node Auxiliary thermal node.

An auxiliary thermal node for corresponding to the average temperature of the FE volume.

.volume_height Out-of-plane height of the problem or connection.

Methods

Class methods are listed below. Inherited methods are not included.

.initialize Initialize the connection.

Initializes the problem matrices etc.

A VolumeConnection is modelled according to the following principles and assumptions:

• The heat flux between the FEA volume and the external node is equal to the temperature difference dT divided by the out-of-volume thermal resistance.
• The temperature difference is equal to the difference between the node temperature and the ** average temperature across this.elements
• For one-sided connections, the out-of-volume thermal resistance is equal the volume height divided by 2 (to account for the average path length), divided by the out of volume thermal conductivity times the combined area of this.elements
• For two-sided connection, this value is again divided by four (4) to account for the halved heat path length ** and the halved flux part half-path
• The heat flux out of or into the FE model is realized as a uniform heat generation density across this.elements, equal to the total flux divided by the combined area of this.elements and the volume height.