This video is taken from the HEAT 100 course on Lumerical University.

## Transcript

The material models used to define the thermal properties of materials for the HEAT solver

fall into one of two types: Solids and Fluids.

Solids include conductors, insulators, semiconductors and alloys.

They are marked by letters M, In, S and A in the material list while fluids are marked

by F. Solids are defined by two general categories

of properties.

The first category is heat transport properties and include density, specific heat, and thermal

conductivity.

Density of a material is its mass per unit volume and the specific heat is defined as

the amount of heat per unit mass required to raise the temperature by one degree.

Thermal conductivity is a measure of how good a material can conduct heat.

Therefore, materials of high thermal conductivity are widely used in heat sink applications

and materials of low thermal conductivity are used as thermal insulation.

Heat transport properties will be used for any type of simulation performed by the HEAT

solver.

Furthermore, specific heat and thermal conductivity can be dependent on temperature and DEVICE

offers the ability to define and enable or disable the temperature dependency model for

these properties.

The models can be accessed by clicking the f(T) button in front of each property.

The second category of properties for solid materials is electrical conduction properties

and includes electrical conductivity.

This is a measure of how conductive a material is in response to an electrical current passing

through it.

Unlike heat transport properties, electrical conductivity is only needed when a “thermal

and conductive” simulation is performed by the HEAT solver.

This property can also have a temperature dependent model defined.

Note that all the parameters mentioned here are defined in SI unit.

Fluids only have heat transport properties as they are usually not electrically conductive.

The heat transport properties of a fluid contain density, specific heat, thermal conductivity,

dynamic viscosity, and thermal expansivity.

Dynamic viscosity is a measure of the fluid's internal resistance to flow and thermal expansivity

represents the tendency of a material to change volume in response to a change in temperature.

It is important to note that the properties of the fluid materials are only used to calculate

the convective heat transfer coefficient at simulation boundaries since the HEAT solver

does not model heat flow in fluids.

All of these properties can have a temperature dependent model defined which can be accessed

by clicking the corresponding button.