CONJUGATE HEAT TRANSFER ANALYSIS ON A GRAPHICS CARD USING ANSYS FLUENT

AIM:

Perform a steady state conjugate heat transfer analysis on a model of a graphics.

Objectives:

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.

Conjugate heat transfer:

Conjugate heat transfer is used to describe the processes which involves variations of temperature within the solids and fluids, due to thermal interaction between the solids and fluids.

The CHT analysis is generally used in places where there is heat transfer taking place for example when a fluid flows through a pipe and the heat of the fluid is transfered to the pipe by convection. CHT analysis is very much useful in analysing the areas where there are two bodies in which heat transfer takes place. when this analysis is used it is easy to calculate the heat transfer coefficient temperature and velocity of a fluid flowing through a certain body.

This type of heat transfer corresponds to the combination of the heat transfer in solids and heat transfer in fluids. heat transfer in solid called as conduction and heat transfer in fluid called convection.

conduction occurs due to the direct molecular collison. the faster kinetic energy collides with the low speed kinetic energy and the heat tranfer occur.

convection process is not happed alone. it is combined with the conduction or radiation. it occurs mostly in the cooling process like Heat sink, Battery cooling, Airflow over the solid object for cooling.

whenever the solid and fluid interface appears, this type of CHT analysis can be done to find the optimum result by using Ansys. It allows the simulation of heat transfer between solid and fluid domains by exchanging the thermal energy at the interface between them.

Geometry:

Model consists of Base

Processor

Fins

Enclosure

MESHING:

BASIC MESHING:

Element size = 0.010289m

No of Elements = 83941

REFINED MESHING:

Element Size 0.005m

Processor Elemnt size = 0.0005

Fins Element size = 0.0005

No of Elements 384352

SET UP:

Steady - PressureBased

Energy - viscous - K-epsilon

Materials:

Processor - copper

Fins - aluminium

Base - Steel

Inlet - velocity(3m/s) - Temperature - 300k

Heat generation rate - 2e7W/m^3

Basic Meshing:

Scalar Residuals:(converged)

Average Temperature:

Temparature:

Velocity:

Wall Heat Transfer Coefficient:

Wall Adjacent Temperature:

Pressure:

Eddy Viscocity:

REFINED MESHING:

Scalar residuals:(converged)

Average Weighted Temperature:

Temperature:

Eddy Viscosity:

Pressure:

Inner wall Temperature:

Velocity:

Wall Heat transfer Coeeficient:

Results:

By the residuals plot it is clearly shown that the solution is converged.

Avg weighted Temperature for case 1 is 301.8 k

case 2 is 301.4k

Refined meshing is done for processor and fins with small element size because the maximum temperature attained at the processor and it is transfered to the fins as these are the parts to attain maximun tamperature so to get the results accurate refining is done for both the parts. by, refining the mesh the values of Temperature and Wall Heat Transfer Coefficient is as follows:

Meshing	Temperature	Wall Heat Transfer
Basic Mesh	315.0k	943.1(W m^2 K)
Refined Mesh	311.2k	983.9(W m^2 K)

The potential hotspots in the model are the areas near the processor particularly fins as it is attaining the max heat generated by the processor through conduction.