CFD-Enabled Optimisation for Microfluidic Heat Transfer Systems

Rapid developments in the electronics industry have led to an increase in the densities of integrated circuits, therefore, finding effective cooling methods to keep the temperature of the electronic components during operation below their critical temperature has become a necessity. Consequently, the current study aims to enhance and optimise the hydrothermal performance for the serpentine minichannel heat sink. Accordingly, a set of objectives have been proposed, and the CFD methodology has been adopted to achieve this aim. Deterministic and probabilistic optimisation strategies have also been employed to find global and robust designs for the considered heat sink.
To enhance the hydrothermal performance of the serpentine minichannel heat sink with plate fins (SMCHS-PF), the effect of the channel width, "1.0 ≤ " "W" _"c" " ≤ 2.0 " mm , and height, "1.0 ≤ " "H" _"c" " ≤ 3.0 " mm, have been investigated. The results showed that the pressure drop (∆P) and thermal resistance (R_th) could be reduced up to, respectively, 94.92% and 10.22% through setting the "W" _"c" =1.5 mm, "H" _"c" =3 mm for mass flow rate (m ̇) of 2 g/s. Besides, vortex generators (VGs) with different size and arrangements were utilised to enhance the performance of SMCHS-PF, and the study exhibited that the existence of the VGs enhanced the heat transfer, but this came at the expense of an increase in pressure losses. The performance evaluation criteria (PEC) has also been used to assess the benefit of adding the VGs. The study has revealed that the SMCHS-PF with vertical in-lined vortex generators (VIVGs) design, which abbreviated as SMCHS-PF-VIVGs, has a superior performance among the studied designs within the range for the vortex generators generator’s radius (r_VG). Regarding the optimisation task implemented for the SMCHS-PF, the results showed that the robust design could be produced with R_th and ∆P higher than those of the global design by 5.7% and 4.3%, respectively.
The current study has also explored the impact of the fin length (F_l) to the secondary channel length (l_sc) ratio (R_FS), fins offset (F_o) and the number of fins (F_n) on the hydrothermal performance of the microchannel heat sink with chevron fins
SMCHS-CF. On the one hand, the study revealed that the pressure drop for the SMCHS-CF, in comparison to the SMCHS-PF, could be reduced by 28% via increasing F_n from 6 to 18 for l_sc = 0.25 mm, but this reduction was not exceeded 10% for l_sc = 1.0 mm for the same range of F_n. On the other hand, R_FS has a small effect on thermal resistance (R_th), and the findings show that the maximum reduction in R_th was 7%. Furthermore, the results revealed that lowering the R_FS from 3 to 1 can reduce the pressure drop by 14%. The probabilistic optimisation results indicated that thermal resistance and pressure drop of the robust design were higher than those of the global optimum design by 8.2% and 43%, respectively.
In the current work, hybrid elliptical-rectangular fins have been proposed to replace the chevron fins for the serpentine minichannel heat sink (SMCHS-EF). The effect of the fin parameters, i.e. the semi-minor axis (R_f), the number of fins (F_n), and the fin length to the secondary channel length (R_FS), on the hydrothermal performance have been explored. Introducing the hybrid fins helped in reducing the overall thermal resistance and pressure drop by 10% and 60% in comparison to those for the SMCHS-PF. Besides, increasing R_FS from 3 to 13 has led to reducing the R_th by 7%, which was accompanied by raising ΔP by 47%.