Example4 Heat Radiation of IC by Forced Convection (Transient Analysis)

General

Heat dissipation of an IC on the substrate by the forced convection is solved by the transient analysis.
The temperature distribution and the heat flux vectors are solved.
Unless specified in the list below, the default conditions will be applied.
Obtain this session's project file. (Save the project file before open)

Analysis Space

Item	Setting
Analysis Space	3D
Model Unit	mm

Show Results

Item	Setting
Solver	Fluid Analysis [Bernoulli] Thermal analysis [Watt]
Analysis Type	Transient Analysis
Laminar Flow/Turbulent Flow	Select Turbulent Flow
Meshing Setup	General Mesh size: 5 [mm]

The Transient Analysis tab is set up as follows. The total number of steps is 20. The timestep is 60 seconds.

Therefore, the temperature distributions for 20 minutes are solved.

Tab

Setting Item

Setting

Transient Analysis

Table

Number	Calculation steps	Output steps	Timestep [s]
1	20	1	100

Initial Temperature

25[deg]

To shorten the calculation time, set the large value for convergence judgment. The settings on the high-level setting tab are as follows.

Tab	Setting Item	Setting
High-Level Setting	Nonlinear Analysis	Convergence Judgment (Heat): 1 x 10^-3

Model

The model is a box solid body. The material is Air (000_Air). The boundary conditions of inlet and outlet are set on the left edge and the right edge respectively.

The slip wall outer boundary condition is applied to the top and bottom edges where the boundary condition is not set.

The substrate (VOL1) and IC (VOL2) are solid bodies.

Setting of Body Attributes, Materials, and Mesh Sizes

Body Number/Type	Body Attribute Name	Material Name	Mesh Size
0/Solid	VOL1	006_Glass_epoxy *	0.2
1/Solid	VOL2	001_Alumina *	0.2
2/Solid	Air	000_Air(*)	–

* Available from the material DB

Specific heat is set as follows since it is not set in the material database.

Material Property Name	Tab	Setting
001_Alumina	Specific Heat	800 [J/kg/deg]

IC (VOL2) is set as follows on the Heat source tab.

Body Attribute Name	Tab	Setting
VOL2	Heat Source	1W

Boundary Condition

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Setting
In/Edge	Thermal Fluid	Inlet	Forced Inflow Specify fluid velocity 1[m/s] Inflow Temperature : 25[deg]
Out/Face	Thermal Fluid	Outlet	Natural Outflow
Outer Boundary Condition	Thermal Fluid	Slip wall	–

Results

The figure below shows the temperature distribution after 1[min] = 60[s], 5[min] = 300[s], and 20[min] = 1200[s]

The maximum and minimum values of the temperature scale are 61[deg] and 25[deg] respectively.

For easy viewing of the temperature distributions of the substrate and the IC, the ambient air field is hidden by right-clicking the air body and selecting [Hide Body Field].

The temperature is rising gradually.

1[min]
5[min]
20[min]

The temperature change at the coordinates (0, 0, 3) which is above the IC is plotted as follow.

Again, it can be observed that the temperature is rising gradually.