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Heat Transfer Research
Fator do impacto: 0.404 FI de cinco anos: 0.8 SJR: 0.264 SNIP: 0.504 CiteScore™: 0.88

ISSN Imprimir: 1064-2285
ISSN On-line: 2162-6561

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Heat Transfer Research

DOI: 10.1615/HeatTransRes.2018026607
Forthcoming Article


Taylor Bevis
Bryan Burk
Colorado State University
Jensen Hoke
Colorado State University
Jack Kotovsky
Lawrence Livermore National Laboratory
Julie Hamilton
Lawrence Livermore National Laboratory
Todd Bandhauer
Colorado State University


Packaging high average power laser diode arrays that generate heat at an area average flux in excess of 1 kW cm-2 is a significant engineering challenge. While liquid microchannel coolers have demonstrated up to 11.9 kW cm-2, two-phase microchannel array coolers have not achieved 1 kW cm-2 due to critical heat flux and flow instabilities. In the current study, flow boiling heat transfer was characterized for a 1 × 10 mm heated zone centered over a 5 × 10 mm array of 125 very small channels (45 × 200 microns) with R134a as the phase change fluid. The high aspect ratio channels (4.4:1) were manufactured using MEMS fabrication techniques, which yielded a large heat transfer surface area to volume ratio. A test facility was used to characterize the heat transfer performance of boiling R134a over a range of saturation temperatures (15°C to 25°C), mass fluxes (735 - 2,230 kg m-2 s-1), and heat duties (<110.3 W). During the tests, the calculated outlet vapor quality exceeded 61% and the base heat flux at the heater reached a maximum of 1.1 kW cm-2. The resulting average experimental flow boiling heat transfer coefficients are found to be as large a 13.4 kW m-2 K-1 over the approximately 3 mm two-phase region, with an average uncertainty of ±2.72 %. A substantial amount of heat was spread downstream via the low thermal resistance silicon floor. Specifically, between 29.5 % and 55.1 % of the heat dissipated in the two-phase region was dissipated over the heater. The remaining heat dissipated in the two-phase region was dissipated in the 2 mm of channel downstream of the heater. This suggests that heat spreading from the hotspot played a vital role in dissipating the heat loa