Conjugate Heat Transfer Analysis on a graphics card.

AIM:- Perform the simulation of a steady state conjugate heat transfer of two different mesh size on a given graphics card.

Objective:-

1. Find out the maximum temperature attained by the processor.

2. Prove that the simulation has achieved convergence with appropriate images and plots.

3. Find out the heat transfer coefficient at appropriate areas of the model.

4. Identify potential hotspots on the model.

Introduction

The conjugate heat transfer analysis was introduced after the computers came into wide use. Before this, the emperical relation of proportionality of heat flux to temperature difference with heat transfer coefficient which was the only tool in theoretical heat convection since the times of Newton. This model, based on a strictly mathematically stated problem, describes the heat transfer between a body and a fluid flowing over or inside it as a result of the interaction of two objects. The physical process and the governing equations are considered for the two seperate sub-domains. Matching conditions for these solutions at the interface provide the distributions of temperature and heat flux along the body–flow interface, eliminating the need for a heat transfer coefficient. Moreover, it may be calculated using these data.

The CHT analytical method is used for various applications such as Electronic cooling, Boilers, Heat exchangers, Engine cooling systems etc.

Cooling systems in Graphics card:

Computer cooling is required to reduced waste heat produced by the computer components to keep them within the operating limits. Exceeding the operating limits would cause temprorary or permanent damage to the components. so it is neccessary that the component should be in the permissible limits. Components that are susceptible to temporary malfunction or permanent failure if overheated include integrated circuits such as CPUs, chipsets, graphics card, and hard disks.

Use of heatsinks cooled by airflow reduces the temperature rise produced by a given amount of heat. Attention to patterns of airflow can prevent the development of hotspots. Computer fans are widely used along with heatsink fans to reduce temperature by actively exhausting hot air. There are also more exotic cooling techniques, such as liquid cooling. All modern day processors are designed to cut out or reduce their voltage or clock speed if the internal temperature of the processor exceeds a specified limit.

Geometry

Given geometry was import in ANSYS space claim, topology share option is used to share the all component like printed circuit board, processor,fins to forms conformal mesh. The formation of conformal mesh was very important to see the heat transfer in the graphics card. Enclosure was used to capture the convection heat transfer over the graphics card.

snap shot of fins

snap short of graphics card

Snap short of graphics car with elclosure

Meshing

For beshline meshing 6mm element size is used for the enclosure and 4mm mesh size is used for the graphics card.

For refined mesh 2mm mesh size is used for the enclosure and 1mm is used for the graphics card.

Observation from the above base line and the refined mesh

Setup for both Base line and refined mesh

Solver

Type-Pressure-Based

Velocity Formulation-Absolute

Time-Steady

k-epsilon turbulent model is used, capturing the temperature variation energy equation is used.

Inlet

Velocity-1 m/s

Temperature- 300K

Materials

For temperature distribution insert a plane along Y-axis

Heat generated by the processor=2e8 W/m^3

Comperasion of result between base line and the refined mesh setup

Residual plot

From the residuals graph we can conclude that the simulation converged around 400 iterations in both base line and the refined mesh setup.

When mesh is refined maximum processor temperature decreased

Conclusions:

• The maximum tempreature attained by the proccessor:

Baseline mesh: 632.53K

Refined mesh: 617.12K

• The wall Heat transfer coefficient attained by the proccessor is:

Baseline mesh: 528.28 W/m^2K

Refined mesh: 542.04 W/m^2K

• The maximum velocity attained by the inserted plane on graphics card

Baseline mesh: 1.187 m/s

Refined mesh: 1.23 m/s

• The hotspots in the potential hotspot in the graphic Card was the processor. since the proccessor generates heat due to power comsumption. The main heat source of the graphic card is the proccessor.