A Study of Micro Channels Integrated with Multiple Jet for Chip Cooling
| Autor: | Han-Yang Liu, 劉瀚陽 |
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| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 As chip power densities in electronic equipment increasing to more then 200W/cm2, an effective cooling system is required for computer chips. In this study,A heat sink integrating micro-channels with multiple jets was designed to achieve better heat transfer performance for chip cooling. This study used dielectric fluid FC-72 as working fluid. The cooling fluid was introduced to a 12×12 mm2 heated surface, which had 11 micro-channels, each channel was 0.8 mm high, 0.6 mm wide,and 12 mm in length. There were 3 or 5 nozzles install on each micro-channel. The nozzle diameters were 0.24 or 0.4 mm, and the nozzles spacing varied from 1.5 to 3 mm. In the tests, the saturation temperature of cooling device system was set at 30 and50℃, and the volume flow rate varied from 100 to 810 ml/min.The experimental result showed that heat transfer performance increased with increasing flow rate for single phase heat transfer. However, in two phase heat transfer regime, the influence of the flow rate diminished when it passed a certain limit. For two phase convection, because that the vapor density at 30℃ was almost an half of that at 50℃, the excess vapor interfered the flow within micro-channels. Hence, the superheat temperature of the heat sink at saturation temperature 30℃ was greater than that at 50℃ by about 13.48 ~ 24.72%. For the same flow rate, the surfaces whose nozzles located near the micro- channels exit yielded better heat transfer performance by shortening thetraveling distance of the liquid in the channels. The thermal boundary thickness reduced as the number of nozzles per channel increased, and thus greater boiling convective heat transfer efficiency was achieved. However, when the jet velocity was too fast, jet streams would interfere with each other, resulting in more stagnant eddy current, larger thermal resistance and pressure drop. Except for low flow rate (100 ml/min), the heat transfer performance increased with increasing (s/d) ratios. The thermal resistance decreased with increasing impingement flow rate or increasing input power of every test surface. The best surface had three nozzles of 0.4 mm diameter, which equally divided micro-channels into four segments. It had lowest thermal resistance about 0.0611 K / W. This new cooling device is found to be a promising chip cooling solution for its low thermal resistance for the practical application of electronic cooling. Correlations of heat transfer coefficient of the single-phase and two-phase heat transfer of the micro-channel/jet cooling integrated device have been developed. Compared with the single phase and two phase data, the prediction uncertainties are within ± 25% and ±30%, respectively. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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