## 6.4. Duplicate Objects

In the IR module, the surfaces are only considered on the region pointed by its normal vectors. This option is used to consider both sides (according with the normal vector directions) of the selected objects.

Duplicate objects is used to calculate the material transmission between the both sides of the object. In addition, as with heat sources, duplicate objects radiate heat to the nearby surfaces.

In this example, the plane between the boxes is a duplicated object, in order to assign the duplicate property to an object, select them and click on add button.

Duplicate objects panel

If a heat source is added to one of the boxes, you can see the effect of the transmission and radiation in the following image.

Effect of radiation and transmission in a duplicate surface

### 6.4.1. Duplicate normals on sources

Objects with duplicated normal vectors transfer power through their materials. Taking into account the Impressed sources with constant temperature, the defined temperature will result on power transferred (that may entail temperature variations) in the direction given by their normal vectors. For this reason, the duplication of normal vectors on Impressed sources deserves a special consideration.

Consider a closed object that is defined as an Impressed source with constant temperature. For example, a circle is considered instead of a sphere to simplify the explanations given in this section.

Circle that simplifies a sphere

As mentioned above, constant temperature sources radiate power according to the defined temperature in the direction given by their normal vectors. If the normal vectors are duplicated, the power is transferred through the material, so a variable temperature is obtained in the opposite direction to the normal vectors, as it depends on the rest of environment parameters. Next figure shows how the thermal power is transferred in sources:

Thermal power transmission through the material of a constant source with duplicated normal

According to the direction of the normal vectors on the sphere, two scenarios can be found:

• Normal vectors pointing outside the object. The source radiates a power that depends on its constant temperature outside the object, and power is transferred through the material to inside. This set-up is recommended to study how a material isolates the temperature from outside (with a measured temperature). It could be used to parametrize the materials of a room with the aim of isolating its temperature from outside.

Normal vectors pointing outside the object

Constant temperature outside and transmitted power inside the object

• Normal vectors pointing inside the object. The source radiates a power that depends on its constant temperature inside the object, and power is dissipated through the material to outside. This set-up is recommended to study how a material dissipates the temperature from inside (with a measured temperature). It could be used to parametrize the materials of an engine room with the aim of minimizing the radiated temperature to outside.

Normal vectors pointing inside the object

Constant temperature inside and transmitted power outside the object

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