# Thermal face (3D) / line (2D) region

## Introduction

The face (in 3D) / line (in 2D) regions are:

• either material regions: used to model thin regions in the study domain

• or regions known as non-material regions: used to impose boundary conditions (BC) inside or on the frontiers of the study domain

• + mixed region

## Material regions (thin regions)

Thin regions enable the modeling of conducting regions of small thickness (cracks, air-gap…).

The thin regions are described in the same way as the massive regions, with in addition, the thickness of the regions.

In 3D, the direction of the thermal flux is selected by the user, as indicated in the table below.

Thin region Direction of the thermal flux
no restriction quasi tangential

conducting

(+ heat source q )

thin regions with random k conductivity

thin region with: k2 >> k1

The available thin region for 3D application is of the thermal conductor type.

## Non-material regions

Non-material regions enable the imposing of boundary conditions (BC).

A region…

is a BC that enables one to impose…

It is defined by…

Heat exchange surface

or

heat source

the thermal exchanges (by convection / radiation to infinite / local radiation)

or

a surface density of thermal flux

• coefficients of: convection / emissivity ɛ / absorption α *

• a temperature to infinite for the convection and radiation to infinite

or

• a surface density of thermal flux (in W/m²) (formula with spatial quantities or formula with input/output parameters)

Imposed temperature a temperature

a temperature (formula with spatial quantities or formula with input/output parameters)

Thermal insulated region

a tangential thermal flux

… on the faces/lines that form the region
Note: * for the local radiation the reflection is taken into account and its coefficient is equal to 1 - α

## Conducting region with double heat exchange (3D)

In 3D problems, there can be a specific type of region ( Conducting region with double heat exchange ) that enables the modeling of thin conducting regions with thermal exchanges on both faces.

The region … enables the modeling … It is defined by …

conducting with double heat exchange

( + heat source q)

of a conducting medium (thermal conductivity k volumetric heat capacity ρCp)

a conducting material (conductivity k)

with thermal exchanges on both sides (by convection / radiation)

coefficients of: convection / emissivity an external temperature on both sides

with possibly a heat source (thermal power)

a thermal power : total value (in W) or volume density (in W/m3) (formula with spatial quantities or formula with input/output parameters)

The thermal flux by conduction is assumed to be tangential to the face region.

Note: A face region of the Conducting region with double heat exchange type should have thermally inactive neighboring volume regions, or no neighboring volume regions.