Assessment of an active-cooling micro-channel heat sink device, using electro-osmotic flow. (English) Zbl 1227.80003
Summary: Non-uniform heat flux generated by microchips causes “hot spots” in very small areas on the microchip surface. These hot spots are generated by the logic blocks in the microchip bay; however, memory blocks generate lower heat flux on contrast. The goal of this research is to design, fabricate, and test an active cooling micro-channel heat sink device that can operate under atmospheric pressure while achieving high-heat dissipation rate with a reduced chip-backside volume, particularly for spot cooling applications. An experimental setup was assembled and electro-osmotic flow (EOF) was used thus eliminating high pressure pumping system. A flow rate of \(82 \mu \)L/min was achieved at 400 V of applied EOF voltage. An increase in the cooling fluid (buffer) temperature of 9.6 \(^\circ \)C, 29.9 \(^\circ \)C, 54.3 \(^\circ \)C, and 80.1 \(^\circ \)C was achieved for 0.4 W, 1.2 W, 2.1 W, and 4 W of heating powers, respectively. The substrate temperature at the middle of the microchannel was below 80.5 \(^\circ \)C for all input power values. The maximum increase in the cooling fluid temperature due to the joule heating was 4.5 \(^\circ \)C for 400 V of applied EOF voltage. Numerical calculations of temperatures and flow were conducted and the results were compared to experimental data. Nusselt number (Nu) for the 4 W case reached a maximum of 5.48 at the channel entrance and decreased to reach 4.56 for the rest of the channel. Nu number for EOF was about 10% higher when compared to the pressure driven flow. It was found that using a shorter channel length and an EOF voltage in the range of 400 – 600 V allows application of a heat flux in the order of \(10^{4} W/m^{2}\), applicable to spot cooling. For elevated voltages, the velocity due to EOF increased, leading to an increase in total heat transfer for a fixed duration of time; however, the joule heating also got elevated with increase in voltage.
MSC:
| 80A20 | Heat and mass transfer, heat flow (MSC2010) |
| 76D05 | Navier-Stokes equations for incompressible viscous fluids |
| 76W05 | Magnetohydrodynamics and electrohydrodynamics |
| 80M12 | Finite volume methods applied to problems in thermodynamics and heat transfer |
| 76M12 | Finite volume methods applied to problems in fluid mechanics |
| 35Q30 | Navier-Stokes equations |
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