Design report cpu cooling solution
- 1. DESIGN REPORT CPU COOLING SOLUTION BY: ABHIMANYU SEHRAWAT ,VIRRUJAN SRIBASKARAN PAUL HAMO AND CHUKWUBUIKEM OMEZIRI MARCH 3, 2017 Team: Alpha (α) 1
- 2. Project Description Advanced manufacturing technologies enable increased amount of transistors which develops heat in CPU. Provide a new cooling solution for CPU cooling to maintain the performance of multiple built-in cores. The current CPU design uses a cooling solution via conduction and convection. The heated air is removed using an integral fan. 2
- 3. Main Design Considerations The maximum allowed CPU block temperature is 70 degree C. Design must dissipate 140 W from a 4cm by 4 cm heated copper block The ambient air temperature is 21 degree C The mounting holes for the heat sinks limited to a total of 4 holes . This limitation necessitate the sub-frame implementation to allow for proper heatsink retention and heatsink-to cpu pressure. 3
- 4. Main design considerations contd. Secondary objectives: Maximize performance Must be able to handle a CPU emitting 180 W of Heat Minimize sound Under 40 dBA 4
- 5. Cooling Strategy Heat Absorption Strategy Water block will absorb the heat from the copper Heat Removal Strategy Pumped water will cool the block by dissipating the heat through radiator Overall, the mechanism is based on liquid cooling and additional heat is removed via forced convection. The fans and radiator are coupled together and mounted on board for proper retention 5
- 6. Initial prototype CAD Model Heat sink 1 (water block) Heat sink 2 (radiator) Fan (forced convection) 6
- 8. Physical Model The solution consists of two heat-sinks, a heat sink mounting frame and two fans to remove the heated air from the water passing through the radiator. A pump regulates the water between the reservoir and the rest. A relief valve provides safety feature and controls the flow coming out of the water block . Oriented in such a manner that air flow from one side of the fan is ejected out from the other side. Fabrication: Water block is fabricated using CNC in two separate parts and fastened together using screws. Radiator was bought. 8
- 9. Other components: The heatsink fans are 12 cm x 2.5 cm x 12 cm thick, rated @ 2000 rpm, 0.35 A, 4.2 W) fans capable of 90 cfm . However, these are 12 VDC fans. This allows us to control the voltage and make them run slowly. The air flow rates may be reduced to lower fan capacity. System becomes quieter as well. The fiber-glass pump rated at 13.2 W, 12VDC, 1.1A having max. flow-rate: 8.3LPM Dimensions: 80 mm x 64.4mm x 48 mm. 9
- 11. Water Block Mounting Block and Gasket Clamping mechanism: Gasket: 11
- 12. Thermal Solution Final Assembly: Video 12
- 13. Thermal simulation: Copper base The thermal model will closely follow the mechanical model. The copper channel of the water block is meshed using coarse fineness. Thermal entrance length = 150 mm Boundary conditions applied: a. Convection heat transfer co-efficient ℎ 𝑤𝑎𝑡𝑒𝑟 = 2938 𝑊 𝑚2.𝑘 b. Inlet reference temperature = 303 K c. Base was supplied with heat flux of 24.11 KW/m2 13
- 14. Temperature results Heat-sink (water block maximum case temperature): 50.5 𝑜 𝐶 This also complies with base temperature from initial calculation i.e. 49.5 𝑜 𝐶 Real-case measurement : 55 𝑜 𝐶 Maximum allowable temperature: 70 𝑜 𝐶 14
- 16. Final results Steady-state temperatures: o(Q= 140W): 𝑇𝑎𝑐𝑡𝑢𝑎𝑙 = 48.1 𝑜 𝐶, 𝑇𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 = 49.62 𝑜 𝐶 o(Q= 180W): 𝑇𝑎𝑐𝑡𝑢𝑎𝑙 = 55 𝑜 𝐶, 𝑇𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 = 49.5 𝑜 𝐶 oThe agreement in both the cases is similar due to lower thermal resistance of copper. Maximum overall system resistance: 𝑅𝑡𝑜𝑡𝑎𝑙 = ∆ 𝑇 𝑄 = 𝑇𝑠𝑢𝑟𝑓 − 𝑇𝑎𝑚𝑏.÷ 𝑄 = 55 𝑜 𝐶 − 24 𝑜 𝐶 ÷ 180 = 0.172 𝐾/𝑊 <<0.32 K/W 16
- 18. Conclusions and lessons learned 1. Do not attempt to fabricate components when it is already available in the market. 2. Buy better sealing material. Plumbers putty not adequate for high flow. 3. CAD design does not guarantee a functioning final design. 4. Contact resistance plays a crucial role for heat transfer. 5. Team work and communication is necessary for success of the design. 18