Optimisation of hybrid microchannel heat sink with secondary channel under laminar flow condition

Abstract

Nowadays, thermal management becomes one of the major bottlenecks that restrict the further development of compact electronic devices. This restriction is because of the unpredicted increment of power density in the high-density microchip, which generates high heat flux. To reduce the excessive heat, the CPU throttling technology will slow down the performance of electronic devices by reducing the frequency of microchips. Thus, to ensure electronic devices always perform at their optimum condition, a cooling system with an advanced cooling technique, such as microchannel heat sink (MCHS), is needed to ensure the operating temperature of electronic devices does not exceed the allowable temperature of the semiconductor components. However, conventional MCHS is inadequate to remove the heat flux effectively due to the thermal resistance in the laminar region and pumping power issue. In the present study, the hydrothermal performance of hybrid MCHS designed with the rib-cavity structure was optimised via secondary channel geometry parameters numerically and validated experimentally under laminar flow conditions. Firstly, the numerical approach was initially verified through the validation of the conventional MCHS. Secondly, a comparative study was conducted between the hybrid MCHS with other related enhanced MCHSs, namely, rectangular-rib MCHS, triangular-cavity MCHS, and rib-cavity MCHS. Thirdly, the hydrothermal optimisation of the hybrid MCHS was performed via parametric optimisation of secondary channel angles, secondary channel locations at the cavity structure, and secondary channel widths. Finally, the numerical result was validated experimentally based on the measurement of the Nusselt number and friction factor parameters. The results showed that the secondary channel geometries in the rib-cavity structure of the hybrid MCHS increased the heat transfer performance by 2.1% with the reduction of pumping power consumption by 82.2%. After the parametric optimisation of secondary channel geometry, the hybrid MCHS achieved a performance factor higher than 2.0 at the Reynold number of 450. The performance factor of the optimised hybrid MCHS was 2.02 at the Reynolds number of 450. The highest performance factor achieved by the optimised hybrid MCHS was 2.10 at the Reynolds number of 600 with the minimal entropy generation number of 0.58. The simulation result of the Nusselt number and friction factor showed a good agreement with the experiment, which was less than 20%. With this optimised hybrid MCHS as a cooling device, it can improve the heat transfer performance by 41.3% with a reduction of pumping power consumption by 83.7%. In addition, the coolant consumption has been saved up to 68.9%. Thus, this hybrid MCHS is suitable for a compact electronic device that does not require high energy and coolant consumption for its cooling system. This hybrid MCHS is potentially explored for the usage of other electronic devices and applications. Several interesting aspects may be explored further by investigating the combination of secondary channel geometry with the various shapes of cavity geometry in hybrid MCHS as it affects the recirculation flow formation. Besides that, the utilisation of nanofluid in the hybrid MCHS should be considered together with the concave dimple geometry as the geometry can reduce the surface friction between the nanofluid and channel wall.