Week 6 - CHT Analysis on a Graphics card

Aim: Analysis of steady-state conjugate heat transfer using a graphics card model

Objectives :

1. Run the simulation by varying the velocity from 1m/sec to 5m/sec for at least 3 velocities and discuss the results.
2. Find out the maximum temperature and heat transfer coefficient attained by the processor.
3. Prove that the simulation has achieved convergence with appropriate images and plots.
4. Identify potential hotspots on the model.

Introduction:

Conjugate heat transfer analysis addresses the heat transfer between a body and a fluid running over or inside it as a result of interaction between two objects. It is based on a mathematically structured problem. The details of the temperature distribution and heat flux along the interface at the matching interface eliminate the need to calculate the heat transfer coefficient. Additionally, it is possible to determine the heat transfer coefficient later.

Numerical approaches are one of the simplest ways to realise conjugation. Iterative methods are used to set and solve the boundary conditions for the interface between a fluid and a solid. Other than by using the hit-and-miss approach, there is no way to make accurate assumptions about the values of the initial boundary condition for convergence.

Application:

The conjugate heat transfer methods have improved as a modelling and research tool for engineering systems and natural phenomena in a variety of fields, such as aerospace and nuclear reactors, thermal goods processing, food processing, complex medical procedures, ocean thermal interaction, and metrology.

Through the design of heat sinks and heat exchangers for the waste treatment plant, CHT has greatly improved the cooling performance of electronic equipment in recent years. The exhaust port system is one such CHT use.

Solving & Modelling approach

• Graphic card file is loaded into the spaceclaim
• The graphics card consists of a processor, PCB base, aluminum fin base, memory cards, and capacitors.
• The solid and liquid volume under consideration are both necessary for CHT analysis, and Spaceclaim offers a volume extract option for choosing edges for fluid volume. In this case, the solid and liquid volume under consideration are air and the components of the graphics card.
• the underlying theory of how air carries away the heat produced by the CPU. The aluminium fin is utilised to increase the heat transfer surface area.
• The share topology is configured to make the mesh conformal and to lower interpolation error.
• The meshing window is then loaded, where the named selection is made and the baseline mesh and refined mesh are set.
• The construction of the material is chosen with the fluid material and the solid material separated.
• To comprehend the behaviour of temperature, velocity, and surface heat transfer coefficient at the interface, the relevant contour images and graphs are reviewed.

Geometry:

GRAPHICS CARD MODEL

PBC BASE

PROCESSOR

FINS BASE

THE MODEL HAS BEEN SHARED FOR MESHING

MESHING

BASELINE MESH DEFUALT SIZE HAS 10.289mm

THEN ADD THE SIZING FOR THE FINS AND PROCESSOR , PCB BASE HAS 1mm SIZE AND MESH SIZE HAS THE 8mm

TOTAL CELL COUNT IS 1,49,333

SETPUT PART

MATERIAL SELECTION

PART	MATERIAL	DENSITY(P)	SPECIFIC HEAT(Cp)	THERMAL CONDUCTIVITY (K)
FINS BASE	ALUMINIUM	2719	871	202.4
PROCESSOR	SILICON	2330	703	153
PCB BASE	FR-4	1850	1300	0.27

BOUNDARY CONDITION

INTIALLY WE HAVE TAKEN THE 1M/S IN INLET CASE-1

HERE, THE IN PROCESSOR IS THE HEAT GENERATED FROM THAT SO, WE NEED GIVE THE SOURCE TERM AND GIVE THE ENGERY SOURCE

The processor is assumed as the only source of heat. The heat generated by the processor is calculated as:-

Graphics Card Power = 1W

Volume of the card = 8 x 8 x 1 = 64mm^3

= 64e^-9 m^3

Heat Generated= P/V

= 1/64e^-9

Heat Generated = 15625000 w/m^3

case 1 inlet 1m/s

WE CAN SAY THAT OUR SOLUTION IS CONVERGED BY SEE THE MAX TEMP AND HTC PLOT THAT AFTER SOME ITERATION THE DEVIATION IN THE PLOT IS CONSTANT

RESULT

TEMPERATURE CONTOUR

VELOCITY CONTOUR

VECTOR CONTOUR

STEAMLINE CONTOUR

HOTSPOT AREA IN THE FINS

case 2 inlet 3m/s

WE CAN SAY THAT OUR SOLUTION IS CONVERGED BY SEE THE MAX TEMP AND HTC PLOT THAT AFTER SOME ITERATION THE DEVIATION IN THE PLOT IS CONSTANT

RESULT

TEMPERATURE CONTOUR

VELOCITY CONTOUR

VECTOR CONTOUR

STEAMLINE CONTOUR

HOTSPOT AREA IN THE FINS

case 3 inlet 5m/s

WE CAN SAY THAT OUR SOLUTION IS CONVERGED BY SEE THE MAX TEMP AND HTC PLOT THAT AFTER SOME ITERATION THE DEVIATION IN THE PLOT IS CONSTANT

RESULT

TEMPERATURE CONTOUR

VELOCITY CONTOUR

VECTOR CONTOUR

STEAMLINE CONTOUR

HOTSPOT AREA IN THE FINS

COMPARISION OF CASES

CASES	MAX-TEMP OF PROCESSOR(K)	HTC-PROCESSOR	AVG-TEMP OF PROCESSOR(K)
CASES 1-1m/s	329.868	5.749	329.703
CASES 2-3m/s	314.725	13.710	314.573
CASES 3-5m/s	310.934	21.068	310.787

MESH INDEPENDENT STUDY - TAKEN THE CASE 3

IN THIS I HAVE GIVEN THE SIZING AS 0.3 TO THE FINS AND PROCESSOR , PCB BASE

SO, THE MESHING IS MORE REFINED

HERE MESH CELL COUNT ALSO INCREASE AS 3,67,746 ELEMENTS

SOLUTION

RESULT

TEMPERATURE CONTOUR

VELOCITY CONTOUR

VECTOR CONTOUR

STEAMLINE CONTOUR

HOTSPOT REGION AREA IN FINS

COMPARISION FOR THE CASE 3 COARSE AND FINER MESH

CASES	MAX-TEMP OF PROCESSOR(K)	HTC-PROCESSOR	AVG-TEMP OF PROCESSOR(K)
CASES 3 COARSE	310.934	21.068	310.787
CASES 3 FINER	310.919	20.836	310.771

FROM THE COMPARISION THE HAS THE MESH IS FINER THE RESULT IS NOT VARIED SO, INCREASING THE MESH SIZE IS NOT CHANGing THE RESULT

CONCLUSION

• As the number of elements increases the accurate results of temperature distribution is obtained but when mesh is more finer the result is going to be same.
• From the comparision table of cases , it is fairly notable that, the net temperature of components of graphics cards decreases with an increase in inlet velocity.
• Hence it can be inferred that a higher inlet velocity results in better cooling and lower the average temperature thus keeping the components safe from damage.
• Furthermore, it can be observed that the temperature of components increases as the inlet velocity decreases from 5 m/s to 1m/s, also proving that higher velocity results in better cooling.