本研究擬以數值方法針對奈米氧化鋁微粒／相變化膠囊懸浮液於平行毫米熱沉流道內強制對流熱傳遞相關流動/溫度場特徵進行模擬分析，探討其對流熱散逸性能/效益。單一矩形毫米流道內三維流動場之數學模式係採用擬渦度-速度(Pseudo-Vorticity-Velocity)模式建構，並以有限差分/體積法建立離散數值模式。本研究所探討毫米熱沉底板厚度為5.0 mm，單一矩形流道之尺寸為：長50.0 mm、寬1.0 mm、高1.5 mm，且平行流道間隔板(鰭片)厚度為2.1 mm。數值模擬所考慮相關參數及其變化範圍為：奈米相變化膠囊懸浮液內含相變化材料體積分率， = 2%、10% (質量分率， 1.61%、8.05%)；奈米流體內含氧化鋁體積分率， 2% (質量分率， 7.3%)；進入單一流道之流體體積流量， =87.69~876.9 cm3/min ( = 200~ 2000)；由熱沉底部所輸入熱通量， =10 W/cm2及20 W/cm2，。本研究所得數值模擬結果顯示：奈米相變化膠囊懸浮液在高流量及高濃度條件下流經毫米流道熱沉，相較於純水，可產生抑制壁溫及提升平均熱傳遞係數效益分別達2.3%與8.2%，並大幅降低熱沉之最大熱阻6.9%；至於奈米氧化鋁懸浮液，在低流量及高熱通量下流經毫米流道熱沉時，其壁溫抑制及平均熱傳遞係數增強之效益可分別達到2.6%及8.4%，且可致使熱沉之最大熱阻下降達4.8%。此外，奈米相變化懸浮液或奈米氧化鋁懸浮液，相較於純水，其黏度均呈大幅上升，導致所預測流經毫米熱沉時所致之壓降亦呈巨幅上升，可分別達4.5倍與1.5倍。

The present study aims to examine, via three-dimensional numerical simulations, laminar forced convection cooling efficacies of using water-based suspensions of nano-encapsulated PCM (NEPCM) or Al2O3 nanoparticles in a rectangular mini-channel heat sink. The geometric dimensions for a unit mini-channel of the multi-channel het sink considered are 1.5 mm in height, 1.0 mm in width, and 50.0 mm in length with a separating fin of thickness of 2.1 mm. A homogenous mixture formulation by means of the pseudo-vorticity-velocity formulation together with the energy equation was adopted to describe the three-dimensional heat and fluid flows of the water-based suspensions considered in a single mini-channel of the multi-channel heat sink. Numerical simulations for the laminar forced convection in the mini-channel heat sink have been performed for the relevant parameters in the following ranges: the volumetric fraction of PCM dispersed, ϕpcm= 2% and 10% (equivalently, the mass fraction of PCM, ωpcm= 1.61% and 8.05%); the volumetric fraction of Al2O3 nanoparticles dispersed, ϕnp= 2% (equivalently, the mass fraction of Al2O3 nanoparticles dispersed, ωnp= 7.3%); the volumetric flow rate entering single mini-channel, = 87.69 - 876.9 cm3/min (equivalently, = 200 – 2000); and the heat flux imposed on the bottom surface of the het sink, = 10 and 20 W/cm2. The numerical results obtained clearly reveal that using the water-based suspension of NEPCM to replace the pure water as the coolant in the mini-channel heat sink can produce marked enhancement of 2.3 % and 8.2% in the wall temperature suppression and the averaged heat transfer coefficient, respectively, under the condition of high flow rate and low heat flux. On the other hand, using the water-based suspension of Al2O3 nanoparticles as the coolant, enhancement of 2.6% and 8.4%, respectively, in suppressing the wall temperature and the averaged heat transfer coefficient of the mini-channel heat sink were predicted numerically. Adversely, resulted from their drastic increase in dynamic viscosity over the pure water, the pressure drop and the pumping power required for the water-based suspensions of NEPCM or Al2O3 nanoparticles through the mini-channel heat sink appear highly uplifted to 4.5 times and 1.5 times, respectively, compared with the pure water.

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