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.

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;´

Properties

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

.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.