Abstract
The dimension of electronic devices become smaller and smaller and it is of significant 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 × 5 mm. The saw-tooth topology on the bottom of minichannel was manufactured by wire-cut EDM. The saw-tooth structure is with a pitch of 1 mm and three different tip angles ( 30 ∘,45 ∘, and 60 ∘) and two different tooth heights (0.5 and 0.75 mm). This study employs HFE-7100 refrigerant, which is of low GWP, as the working fluid to investigate the boiling heat transfer in three kinds of surface structures (plain, parallel saw-tooth and counter saw-tooth). The mass flux ranges from 63 kg/m^2s to 285 kg/m^2s. The experimental results show that the critical heat flux increases with increasing mass flux and enhancement of critical heat flux due to saw-tooth structure. For the structure with a tip angle of 45 ∘and tooth height of 0.5 mm. The critical heat flux in the parallel and counter saw-tooth minichannel are greater than that of the plain minichannel by 46.7 % and 40.2 % for a low mass flux of 127 kg/m2s. This indicates that the critical heat flux is significantly enhanced by the saw-tooth structure with either parallel or counter flow design for low mass flux. On the other hand, compared to the plain minichannel, the critical heat flux of the parallel and counter saw-tooth minichannel are increased by 1 % and 17.1 %, respectively, for a large mass flux of 285 kg/m2s. A saw-tooth structure with counter flow design may significantly enhance the critical heat flux. Furthermore, a tip angle of 60 ∘and height 0.5 mm in minichannel with counter flow is found to perform best.