近年來隨著電子元件的高速發展，其總功率不斷增大，但尺寸卻越來越小，熱流密度因而持續增加，因此如何解決散熱來保持產品壽命成為一個重要的問題。但當電子元件尺寸小到微米或亞微米時，一些在常規大尺度流動中可以被忽略的因素如滑移邊界都可能在流力與熱傳中佔據主導地位，從而導致較為特殊的微尺度熱流現象，如滑移速度(Slip Velocity)、溫度跳躍(Temperature Jump)等。這些現象的出現通常會對熱傳有較大的影響，因而揭示其影響機制並改善熱傳增益變得非常必要，尤其當流體為脈動流時，更值得探討。本文使用晶格波茲曼法(Lattice Boltzmann Method，簡稱LBM)探討滑移與脈動效應對以空氣為工作流體之肋條微通道(高0.68-34μm) 熱傳增益之影響，由於變化參數較多，本文內文分為穩態流和脈動流兩部分。
穩態流部分，在固定肋條高度（〖H_r〗^*=0.25）等條件下，改變截距比(PR)、努森數(Kn)和雷諾數(Re)來觀察其熱傳增益( )與壓力損失( )的變化。模擬結果顯示， 會隨著PR增加而增加， 則隨著PR增加而減少； 和 均會隨著Kn增加而減少； 會隨著Re增加而減少， 隨著Re增加而增加。其中在PR=3，Kn=0.001，Re=0.1時擁有最佳的熱性能係數(Thermal Performance Factor, 簡稱TPF)，其為文獻中全展平滑管道與具肋條管道最佳值的2倍。此外為方便工程應用，本研究還提出 和 對PR、Kn、Re經驗關係式。
脈動流部分，為了進一步提升熱傳效果而將管道的穩態流入口改為三角形脈動入口並改變斯特勞哈爾數（St），在低Re下(1≤Re≤10)，因軸向熱傳導效應大於熱對流效應，其 和 隨St都沒有太大的變化。而在固定Kn=0.005，〖H_r〗^*=0.5，增加Re至80時， 和 均先隨著St增加而增加，且在St=1.0時為峰值((Nu) ̅⁄〖Nu〗_0 =1.67，f ̅⁄f_0 =19.69)，之後再下降, 在St=1.0時較穩態流(St=0.0)增加了30%。綜合前人文獻平滑管道與具肋條管道之滑移穩態流 - 數據，本研究以LBM模擬具肋條管道之脈動流未見先前文獻報導，其熱傳增益在f ̅⁄f_0 =3-20區間內最大值可達1.67。先前文獻及本文皆發現穩態流時，溫度滑移與速度滑移對熱傳壓損影響一致，然而本文於脈動流首度發現有相同趨勢。

With the rapid development of electronic devices in recent years, there is an increasing trend in their power consumption and decreasing trend in their sizes, which results in increasingly large heat flux generation. To maintain an acceptable product life, it becomes imperative to dissipate the heat efficiently. As the dimension of electronic devices approaches micrometer or sub-micrometer, some phenomena that can generally be neglected in the macroscale continuum flow, such as the slip boundary condition, may play a pivotal role in the microscale thermal flow. The typical impacts include considerable slip velocities and temperature jumps on the boundary wall which may significantly affect the heat transfer. This necessitates a thorough understanding of the heat transfer mechanism and heat transfer enhancement, especially in pulsatile flows. In this study, the lattice Boltzmann method (LBM) is used to investigate the effects of flow slip and pulsation on heat transfer enhancement in a ribbed microchannel (channel height from 0.68-34 μm) with air as the working fluid. Considering the various parameters examined, the main content of this work is divided into two parts: steady-state flow and pulsating flow.
For the steady-state flows in the microchannel with a fixed rib height (〖H_r〗^*=0.25), the heat transfer enhancement ( ) is observed to increase with increasing pitch ratio (PR) and Reynold number (Re) and decrease with increasing Knudsen number (Kn). In contrast, the pressure loss ( ) is found to decrease with increasing PR and Kn and increase with increasing Re. The highest thermal performance factor (TPF) occurs at PR=3, Kn=0.001 and Re=0.1, which is two times that of the best value for smooth and ribbed channels. In addition, for the convenience of engineering application, the empirical correlations of and versus PR, Kn and Re are proposed.
For the pulsating flows, the original steady flow inlet is changed to a pulsating velocity inlet with triangular waveform and the corresponding Strouhal number (St) is varied. At relatively low Re (1≤Re≤10), and are found insensitive to St since the axial heat transfer effect is much greater than that of the heat convection. However, as Re is increased to 80, and at Kn=0.005 and 〖H_r〗^*=0.5 both rise and fall with ascending St, with peak values 1.67 and 19.69 appearing at St=1.0. The peak is 30% higher than that of the steady-state flow (St = 0). Finally, compared with previous - data for steady slip flows in smooth and ribbed channels, the pulsating slip flows in present ribbed channels by LBM simulation have not been reported in the open literature, and improve to the highest value 1.67 for f ̅⁄f_0 =3-20. Furthermore, it is found for the first time that the effects of velocity slip and temperature jump on heat transfer and pressure loss in pulsating flows are similar to those reported in steady flows.
Keywords: Microchannel, Slip Flow, Pulsatile Flow, Microstructure, Conjugate Heat Transfer, Lattice Boltzmann Method

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