Week 5.3 - Forced convection Analysis
Aim: To perform forced convection analysis for given model.
Introduction:
* Given CAD model has not simplified as per Icepak understandable bodies. So, created flow structure in Ansys workbench and simplified model with help of spaceclaim.
* Once done simplification, checked all geometries in icepack and created fine mesh.
* The given model has fan and heat sources. Solver setting has been done set according to forced convection analysis.
Geometry:
* The model has imported in space claim. During the quick analysis, all objects was combined and shown as single object.
* Separated them with help of Split command and used required level of simplification to all objects.
Simplified Geometry
Fan
Mesh:
* Opened Icepak model in Ansys workbench. During first level of meshing, the count was nearly 1 million. Then, with help of no-conformal meshing the mesh count has reduced drastically and ensured visual and quality checks are within the limitation.
* Used 2D fan instead of 3D model and set volumetric fixed flow is 10cfm. Considered BGA as 20W and all mosfet dies are 2.5W heat generated sources.
Non-Conformal mesh assembly
Mesh Control
X-Axis cut plane
Y-Axis Cut plane
Z-Axis cut plane
Solver Setting:
Basic Parameters
Variable Solved : Flow,Temperature
Radiation : OFF
Flow regime : Turbulent-Zero equation
Natural convection : Gravity Vector- OFF
Used Default material values
Used Steady state analysis
Solution Initialization : 0 m/s
Boussinesq eqaution : Operating pressure - 101325N/m2
Basic Setting
Numer of iteration:100
Convergence Criteria: Flow(0.001), Energy(1e-7), Joule heating (1e-7)
Parallel Setting
Parallel processor : 4
GPU used : 1
Specify moitor point output frequency : 10
Enabled autosave interval
Advanced Setting
Discretization scheme
Pressure- First
Momentum - First
Temperature - First
Under relaxation
Pressure- 0.3
Momentum - 0.7
Temperature - 1.0
Viscosity - 1.0
Body forces - 1.0
Linear Solver
Pressure - Type(V), Termination criterion(0.1), Residual reduction tolerance(0.1), Stabilization(None)
Momentum - Type(flex), Termination criterion(0.1), Residual reduction tolerance(0.1)
Temperature - Type(F), Termination criterion(1e-6), Residual reduction tolerance(0.1), Stabilization(None)
Used double precision
Post Processing:
The obtained plots are plotted here. Here, we can see maximum temperature has raised near BGA (47.7 degree celsius). With out fan the model was generated more heat. Now, temperature raising inside the model has reduced with help of fan.
Residual plot
Contour temperature plot by object face(node)
Heat Generated on BGA
Contour Speed plot by object face(node)
Vector Velocity magnitude plot by object face(Node)
Z-axis cut plane temperature plot:
X-Axis cut plane temperature plot:
Y-Axis cut plane temperature plot:
Conclusion:
We are successfully performed forced convection analysis for given model and shown maximum temperature value with all relvent plots.