THERMAL DESIGN OPTIMIZATION OF A TELECOMMUNICATION ELECTRONIC BOARD

Applications used:

Solidworks, and Ansys-Fluent

By

Nabeel Fathinabeelg@gmail.com

• This study demonstrates the simulation of the heat dissipation of a telecom equipment electronic board.

• The velocity profile, and the temperature distribution of the surface of the board are exhibited.

• The study suggests a hardware modification to improve the temperature consistency on the board for a given air flowrate.

• The temperature consistency is quantified by the difference between the highest and the lowest temperatures on the board.

• Inconsistency in temperature might cause unwanted hot spots on the board.

Introduction

Problem DescriptionThe PDSN subrack contains several boards that are installed vertically in the board cage. The fan module enforce a vertical airflow from the bottom to the top. The boards dissipate heat to the vertical air current.

Air Inlet panel

Air Exit panel

Boards

The cold air enters the subrack at the air inlet panel located at the lower front side of the subrack. The air heats up as it passes over the vertical hot boards, and then leaves at the air exit panel located at the top of the backside.

Airf

low

Air block surrounding the board

Airf

low

Due to the similarity of the boards, only one board was involved in the simulation.

Air Inlet panel

Air Exit panel

Board

Air Exit

Problem Simplification

The geometry of the board and the air surrounding it were modeled using solidworks, and then imported by Ansys workbench14. Ansys-fluent was used for fluid flow and thermal simulation.

Geometry and Boundary Conditions

Air Inlet

Air exit

Symmetry walls

Heat generation

in the boardBoundary Conditions:1. Inlet velocity: 3m/s.2. Inlet air temperature 291oK3. Heat generation per board:

100W.

4. Symmetry was assumed at both sides of the geometry.

5. Laminar flow is assumed.

MeshingThe geometry of the board and air was meshed using size meshing of 0.01m.

Air block surrounding the board

Board handle

Board

ResultVelocity and temperature distribution of the surface of the board.

Velocity distribution Temp distribution

High inconsistency of the temperature distribution over the board surface. Highest ∆T is 42 K

Air Inlet

Air exit

Air Inlet

Air exit

Unwanted hot spot

Modification 1To reduce the inconsistency in the temperature distribution over the board surface, the airflow was manipulated by adding deflector1.

Deflector 1

Board handle

Air

MeshingThe geometry of the board and air was meshed using size meshing of 0.01m.The air surrounding the deflector was meshed using inflation, and surface size meshing of 0.001 m.

ResultVelocity and temperature distribution of the surface of the board ( Deflector 1).

Velocity distribution Temp distribution

Improved consistency of the temperature distribution over the board surface. Highest ∆T is 36 K

Air Inlet

Air exit

Air Inlet

Air exit

Unwanted hot spot

Modification 2Further modification was applied to the hardware. The geometry of deflector1 was modified into deflector2.

Deflector 2

Board handle

Air

MeshingThe geometry of the board and air was meshed using size meshing of 0.01m.The air surrounding the deflector was meshed using inflation, and size meshing of 0.001 m.

Mesh inflation layers

ResultVelocity and temperature distribution of the surface of the board ( Deflector 2).

Velocity distribution Temp distribution

High inconsistency of the temperature distribution over the board surface. Highest ∆T is 33 K

Air Inlet

Air exit

Air Inlet

Air exit

Conclusions

• Temperature consistency can be improved by manipulating the airflow over the board.

• Deflectors can be used to manage the airflow.• Testing deflectors with different geometries, and using multiple

deflectors at the same time should be considered in future studies.

Remarks

• The solution is mesh dependent, and further mesh refinement is required, however that was not conducted due to the limited computational power available during conducting this study.

• In this study it was assumed that the board is generating heat, while in real practice electronic chips attached to the board are generating heat.

• Numerical analysis can only give approximate results. To obtain more accurate results, experimental analysis is advised.

The End