General
The model is the same as Exercise 7: A heat source is placed on a substrate, and there is a forced air flow for cooling in parallel to the substrate. The heat radiation is analyzed under the transient condition.
The heat transfer coefficient is acquired manually.
To acquire it automatically, see “Ex.1 of Simple FluidThermal Analysis”.
The temperature distribution and the heat flux vectors are solved.
Unless specified in the list below, the default conditions will be applied.
Item 
Settings 
Analysis Space 
3D 
Model unit 
mm 
Item 
Settings 
Solver 
Thermal Analysis [Watt] 
Analysis Type 
Transient analysis 
Options 
N/A 
The transient analysis is set up as follows. The total number of steps is 20. The time step is 30 second.
Therefore, the temperature distributions for 600 seconds are solved.
Tabs 
Setting Item 
Settings 

Transient analysis 
Table 


Initial Temperature 
25[deg] 
The same as Exercise 7. The material properties and the boundary conditions are the same as well.
The substrate (VOL1) and the heat source (VOL2) are created as solid body box, and the heat amount is defined in the body attribute of VOL2.
The heat transfer coefficients for the top and bottom faces of the substrate and the top face of the heat source are calculated basede on the simplified equation.
Body Number/Type 
Body Attribute Name 
Material Name 
0/Solid 
VOL1 
006_Glass_epoxy * 
1/Solid 
VOL2 
001_Alumina * 
* Available from the Material DB
The heat source of VOL2 is set up as follows.
Body Attribute Name 
Tab 
Settings 
VOL2 
Heat Source 
1[W] 
The heat transfer coefficients for the forced convection are calculated as follows. For the details, please refer to the Heat Transfer Coefficient for Forced Convection
To acquire it automatically, see “Ex.1 of Simple FluidThermal Analysis”.
h = 3.86 x (V/L)0.5xC [W/m2/deg]
where
Air flow V=1[m/s]
On the top and bottom faces of VOL1: Characteristic length L=0.05, C=1 > h=17.26
Top face of the heat source (VOL2): Characteristic length L=0.02, L’=0.015, C=1 * > h=27.3
*
The thickness (d) of the speed boundary layer at the edges of the heat source is calculated as follows
d=0.0182x(L’/V)0.5= 2.3[mm]
This is close enough to the thickness of heat source, so we set C=1.
Boundary Condition Name/Topology 
Tab 
Boundary Condition Type 
Settings 
BC1/Face 
Thermal 
Heat Transfer/Ambient Radiation 
Heat transfer coefficient: 17.26 [W/m2/deg] Ambient temperature: 25[deg] 
BC2/Face 
Thermal 
Heat Transfer/Ambient Radiation 
Heat transfer coefficient: 27.3 [W/m2/deg] Ambient temperature: 25[deg] 
The temperature distributions at each time are shown below.
At Minimum/Maximum Value on the Contour tab of [Graphics Setup], deselect “Automatic” and set 25 => 62.
The temperature vs. time is plotted for the center of the heat source.
It is getting stabilized in 600 seconds.