Development of a High Performance Heat Sink Based on Screen-Fin Technology

1. Development of aHigh Performance Heat SinkBased on Screen-Fin Technology Chen Li and Richard Wirtz Mechanical Engineering Department University of Nevada, Reno March 11, 2003 Research sponsored by the Missile Defense Agency through the Air Force Office of Scientific Research, contract F49620-99-1-0286 SemiTherm 19

2. Motivation Woven Mesh Structures (AORS): • Wide range of porosity, surface area to volume ratio, effective thermal conductivity • Easy control of ,  and ke through mesh parameters • Anisotropy: Large ke (to 78% base material value) in a particular direction SemiTherm 19

3. Heat Exchanger Implementation Park, Ruch and Wirtz [2002] SemiTherm 19

4. Two Approaches • 3-D Weaves • Dense structures, High ke, , heat transfer and pressure drop, [Wirtz et al, Itherm, 2002] • Screen Laminates •  = 90 Flow, Heat Transfer/Pressure Drop Char: Park, Ruch and Wirtz, AIAA 2002-0208 • Wide ranging  and , high ke : Xu and Wirtz, IEEE CPT Vol. 25, pp. 615 – 620, 2003 SemiTherm 19

5. d= 0.5mm  = 90 f Red2 Screen Laminate Performance Air Wirtz and Park, pending AIAA JTHT SemiTherm 19

6. Woven Mesh Copper Base One-row serpentine screen-fin heat sink Screen-Fin Design Concepts Pressure Drop Heat Transfer SemiTherm 19

7. Laminar Flow Element Blower Heat Sink Heater Insulation G0, Tf,0 Schematic of Experiment Setup Experiments,   90 Measure P(G) & U(G) and back-calculate f and St SemiTherm 19

8. Pressure Drop Correlation, nrow = 1 Air, Pr = 0.69 θ SemiTherm 19

9. J θ ε=0.677 Pr=0.71 3° 6.2 ° 9.5° > 20° 8°< θ<14° J θ Eq.(12) Stanton Number Correlation, nrow = 1 SemiTherm 19

10. Multiple-Row Performance SemiTherm 19

11. H= 38.1mm 2 G0 W0=63.5mm One-row Heat Sink Segment Q=9439 cm3/sec nrow ΔP=62.27 Pa θ=11° Screen-Fin Thermal Characteristics SemiTherm 19

12. Optimized Prototype, P = 0.25” H2O Lo = 63.5mm, Wo = 76.2 mm, H = 38.1mm (3” x 2.5” x 1.5”) SemiTherm 19

13. Plate-Fin Heat Sink Screen-Fin Heat Sink Parallel Plate Fin Heat Sink Screen Laminate Fin Heat Sink cm3/s Performance Comparison Equal Flow Rates Equal Pressure Drop SemiTherm 19

14. Conclusions - Correlations • Correlations of friction factor and Colburn j-factor show that coolant pressure drop and Stanton number are sensitive to the angle of incidence of the superficial mass velocity. • The modified friction factor is found to increase rapidly as  0, while the modified Colburn j-factor is observed to  0. As a consequence, configurations with  90 will maximize the heat transfer rate while they minimize coolant pressure drop. • Configurations having  = 90 generally present a minimum heat transfer surface area. Consequently, there is an optimum value of  for a given heat sink configuration. SemiTherm 19

15. Conclusions – Heat Sink Application • The design attributes of a air-cooled heat sink with a footprint of 3” x 2.5” and 1.5” tall screen–fins deployed as multiple rows in a serpentine configuration is optimized to operate at P = 0.25 in H2O. • The overall conductance is found to be 4.3 watt/C (0.23 C/watt) with 8 liter per sec (17 cfm) coolant consumption. SemiTherm 19