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

## Transcript

The Heat Transport or HT solver is a physics-based simulation tool for thermal analysis in solid-state

devices.

The solver can evaluate the heat transport equation independently, or self-consistently

solve the coupled system of equations for heat transport and conductive electrical transport

(also known as Ohm’s law) to calculate thermal response in an electrically driven system.

The heat transport solver calculates the solution T (the temperature) to the heat transport

equation in a solid medium.

The heat transport solver discretizes and solves the heat transport equation or the

coupled heat transport and electric current equations on a mesh grid in two or three dimensions.

The materials used in the simulation may be categorized as solids or fluids.

Each type of material has an associated model that describes its thermal behavior.

Domains of fluid materials are not directly simulated.

Fluids can only form boundary conditions for solids in the simulation that depend on their

physical properties.

The heat transport solver uses a finite-element mesh in the form of triangles in 2D and tetrahedra

in 3D, such as the one shown here.

The solution to the system of equations used to determine the physical quantities of interest

is estimated from the discrete formulation of those equations.

Fundamental simulation quantities such as material properties, geometry information,

temperature, and electrostatic potential are calculated at each mesh vertex.

A finer mesh (with shorter edge lengths and smaller elements) will better approximate

the exact solution to the system of equations, but at a substantial cost in simulation performance.

As the mesh features become smaller, the simulation time and memory requirements will increase.

DEVICE provides a number of tools, including the automatic and user-defined mesh refinement,

to take advantage of mesh refinement only in places where it’s needed, which allows

you to obtain accurate results, while minimizing computational effort.

Automatic mesh refinement is a feature that automatically uses a finer mesh for example

around the areas where there is a sudden change in properties such as doping and heat generation

to more accurately resolve these changes.

You can see an example of automatic mesh refinement here around the boundaries where a sudden

change in the value of an specific property is detected.

In the next unit, we will learn about different modes of simulation available in the HEAT

solver.