The dimension of electronic devices becomes smaller and smaller and, thus, it is of crucial importance to enhance the heat dissipation from such tiny devices. The present study investigates the boiling heat transfer in a minichannel heat sink with saw-tooth structure on channel surface. The heat sink is comprised of four minichannels with hydraulic diameter of 0.8 mm and made of copper. The dimensions of the base area of the heat sink are 90 mm (length) × 5 mm (width). The saw-tooth topology on the bottom surface of minichannel was manufactured by wire-cut electrical discharge machining (EDM). The height, tip angle, and pitch of the saw-tooth structure are 0.5 mm, 45°, and 1mm, respectively. This study employed refrigerant HFE-7100, which is of low global warming potential (GWP), as a working fluid to investigate the boiling heat transfer in three kinds of surface structures (i.e., plain, parallel saw-tooth, and counter saw-tooth). The mass flux of the HFE-7100 ranged from 64 to 285 kg/m2s. The experimental results showed that the critical heat flux (CHF), compared to the plain minichannel, is improved by 46.7% and 40.2%, respectively, in the parallel and counter saw-tooth minichannels for a low mass flux of 127 kg/m2s. This result indicated that the CHF is considerably enhanced by the saw-tooth structure with both parallel and counter flow designs for the low mass flux. However, the CHF in the parallel and plain minichannels is nearly the same for a large mass flux of 285 kg/m2s. But for a saw-tooth structure with counter flow design, the CHF increases by 17.1% compared to the plain minichannel. Consequently, the experimental results demonstrated that the CHF can be enhanced by using saw-tooth structure on the channel surface.

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