A heat sink with convective boiling in micro-or mini-channels is with great potential to meet the requirement of the high heat dissipation of the electronic devices. This study investigates the flow boiling of HFE-7100, having a suitable boiling temperature at atmospheric pressure and dielectric property, in the minichannel heat sink with the modified surface (namely, the saw-tooth structure). The effect of the system pressure on the boiling characteristics was also studied. The results reveal that the critical heat flux can be significantly improved by introducing the saw-tooth structures on the channel surface or boosting the system pressure as well as by increasing the mass flux. Compared to the non-modified channel, the enhancements of the critical heat flux for the parallel and counter saw-tooth channels are 44% and 36%, respectively, at the small mass flux. The boiling visualization further indicates that the minichannels with the saw-tooth structures interrupt the boundary layer and restrain the coalescence of the bubble, which may be the reason for the critical heat flux enhancement. Moreover, the degree of the critical heat flux enhancement, contributed by the saw-tooth modification of the channel, decreases with an increase in the mass flux.

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.