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Summary: The demand for high cooling capacity heatsinks has been increasingly promoted due to the fast elevated heat generation of modern electronic devices. High‐performance microscale heat exchangers are often accompanied by considerable pressure drop penalty that limits their applications. In order to avoid large pressure drop while maintaining high heat transfer rate, a macroscale curved channel was proposed with applying the periodical wave structure on the channel sidewalls. A three‐dimensional conjugated numerical model was established, and the effects of wave number and average radius on the hydrothermal performance were investigated. It was found that the heat transfer performance in the smooth‐curve channel is significantly improved due to the wavy sidewalls with a moderate pressure drop penalty. The heat transfer enhancement is more noticeable in the channels with more wave units and smaller average channel radius. Furthermore, it was noted that the periodical thermal entrance effect exists on the inner and the outer convective surfaces of curve‐wave channels, which can be attributed to the variations of the secondary flow with the wave direction along the channels. [ABSTRACT FROM AUTHOR]

Summary: The excess heat generated by the modern electronic components and devices leads to a sustained growth in demand for thermal management technologies. Inspired by the features of fractal structures in terms of the periodical interruption of boundary layer and the strong flow mixing, a parametric study is carried out to study the flow and heat transfer performance in the fractal minichannels configured with hexagonal fins. A dimensionless performance factor involving average Nusselt number and average friction factor is defined to evaluate the overall performance with considering heat transfer enhancement and additional friction loss. The parametric effects of branching angle θ (60°‐120°) and relative hexagonal side length α (1.00‐2.00) on laminar hydrodynamics and thermal characteristics in the proposed minichannels are numerically investigated for Reynolds number ranged from 50 to 550. The results emphasize a lower temperature and more uniform temperature distribution on the bottom surface and an advantage of overall performance for the fractal minichannel with hexagonal fins over the conventional straight minichannel. It is noted from the results that the variation of branching angle possesses little effect on the maximum temperature and temperature uniformity of the bottom surface. On the basis of the evolution of the performance factors, the best performance is obtained by the branching angle of 60° and the relative hexagonal side length of 1.50 among the tested configurations, and the maximum temperature and temperature uniformity of the bottom surface are reduced by 16.4 K and 84%, respectively, when comparing with the straight channel as the reference object. This study verified the theoretical conjecture that the application of hexagonal fins in minichannel plays an important role in effectively improving heat transfer in the case of controllable pressure loss. [ABSTRACT FROM AUTHOR]

With the rapid increase of the thermal power of electronic devices, phase change material(PCM) have shown great application prospects in the field of electronic thermal management. However, due to the irregular surface of the electronic device, PCM can only act on the back of the component or the outside of the package, which leads to the occurrence of heat transfer hysteresis. In order to reduce the heat transfer distance between the heat source and PCM, a new type of ER/SAT/DSP composite functional material with thermal control function was prepared in this paper to solve the key technical problem of fluid seamless packaging thermal control. The composite material is encapsulated in a fluid state and will no longer melt after solidification. Through thermophysical experiments and morphological characterization, the results show that when the mass fraction of PCM is 35%, the composite material has the best physical properties and application performance. And after 200 thermal cycles, the leakage rate is only 3.7%. Through the PTC thermal control experiment, the results show that the maximum temperature at different positions of the device for pouring the new composite was reduced by 7.4 °C and 8.1 °C, respectively, and the operation time corresponding to different temperatures was increased by 5.76 times, 5.80 times and 6.98 times, respectively. Therefore, the composite material shows a good thermal control ability for electronic components of any surface shape. [ABSTRACT FROM AUTHOR]