This video is taken from the HEAT Learning Track on Ansys Innovation Courses.
Transcript
In this unit, we will set up the project for a steady-state heat flow simulation in thin-films
as our first simulation with the HEAT solver. As the first step in simulation workflow,
we need to add the materials needed in our simulation. Let’s open the electrical and
thermal material database. This database contains more than 40 common solid materials. There
is also a material type called "Fluid" which applies to any liquid or gas (e.g. Air) present
in the simulation region. In this example, to define the material properties of the silicon
thin film, we will use the material "Si (Silicon)" available in the material database. The material
properties window for silicon has three tabs; Electronic Properties, Recombination, and
Thermal Properties. The first two tabs contain electrical properties of the material which
are used by the CHARGE solver. The third tab contains thermal properties of the material
used by the HEAT solver. For this example, we will focus on the thermal properties of
the materials only. Select the "Si (Silicon)" material from the
material list. Click on the "Thermal Properties" tab which contains the thermal properties
of the material used in the simulation. For the purpose of this example, we will keep
all the properties in their default values and click create to add the material to our
material list in the objects tree. Note that both electrical and thermal properties of
the material will be added to the simulation but when using the HEAT solver, only the thermal
properties which are marked with the icon “HT” will be considered in the simulation.
Next, we need to add air as the second material used in our simulation. To do so, select “Air”
from the list and leave all the thermal properties to their default values. Again clicking create
will add the material to the simulation. Click OK to close the material database. You’ll
notice that Air is marked as fluid. The Structures section of the Design tab can
be used to introduce various types of structures into the simulation volume. To create the
silicon thin film, we will add a rectangle object to the simulation region (also shown
under "geometry" in the "Objects Tree"). Select the rectangle and click the edit button to
edit its properties. We will name it thin_film and set its x span to 10000.1, y span 10000
and z span 10. We will also choose its material to be silicon which was previously added to
our material list. Here, the x span of the thin film is made slightly larger than the
specifications. This is not necessary for the simulation but it is done here to demonstrate
that the length of the simulation region ultimately defines the portion of the film that will
be considered in the simulation if the structure extends beyond simulation region boundaries.
Then we add another rectangle to represent the air in our simulation. Lets name it “air”
and choose the same x and y span as the silicon film and a z span of 30 microns. Select the
material to be air and change the mesh order value to be 5. This will ensure that it only
fills the volume where the silicon thin-film is not present. The concept of mesh order
will be covered later in the course. After defining the geometry of the structure
to be simulated, we can define our simulation region. We leave its dimension to be 2D Y-normal
and keep all boundaries closed. Under the geometry tab, lets set the x span to 10000
microns which is the desired length for our thin film and the z span to 25 to include
air in our simulation. Next, we need to add the HEAT solver. Note
that once the solver is added, all the simulation objects belonging to the HEAT solver become
available under a new tab named HEAT. Lets set the HEAT solver properties. Since we are
performing a thermal-only, steady-state simulation, the solver physics and mode should be set
accordingly. Set the normalization length to 10000. Since we are setting up a two-dimensional
simulation, this parameter will determine the dimension of our structure (which is the
width of thinfilm in this example) in the third dimension. This is needed by the solver
to calculate volume dependent parameters such as dissipated heat power. Under the mesh tab,
we set the minimum and maximum edge length values to 10 um to ensure an adequately refined
mesh based on the dimensions of our device. Lets leave the rest of the settings to their
default values and close the window. To ensure that the simulation materials and
geometry are defined correctly, we can switch to the partitioned volume mode. We can confirm
that the simulation is formed of three domains with a silicon layer in the middle surrounded
by air on the top and bottom. Next, we need to define the boundary conditions
of our simulation. Here we will use a boundary condition to set the temperature at the left
edge of the thin film to a fixed value of 400 K. Click the "Temperature" button from
the Boundary Conditions section of the HEAT tab. Name it “left” and set its mode to
steady state. Since the temperature will be constant, sweep type should be single and
the temperature set to 400. Under the geometry tab, set the surface type to “simulation
region” and check the “x min”. This will assign the boundary condition to the
left edge of thin-film which happens to be the x min boundary of the simulation region.
We also need to define what happens thermally at the interface between air and our thin-film.
To do so, add a convection boundary condition which will model convective heat transfer
between a solid and a gas. Set the ambient temperature to 300, model to constant, and
“h” value to 10. To assign this condition to the interface between air and silicon,
select the surface type material:material and choose air and silicon as material 1 and
2. If you select the boundary condition object while still in partitioned mode, you can observe
where the boundary condition is applied. Finally, we need to add a temperature monitor
to visualize the temperature profile across our thin-film. From the Monitors section of
the HEAT tab, click on the temperature monitor to place a temperature monitor in the simulation.
We will set the type to be linear x to have a one-dimensional monitor along the x direction
and set its x span to 10010. This is larger than the x span of the simulation region.
In such cases, the span of the saved data will be determined by the span of the simulation
region and will ensure that the data is recorded exactly up to the edge of the simulation region.
The simulation setup is now complete and you can save the file. Later in this section,
we will learn how to run and analyze this simulation.