DSpace community: 能源工程研究所

填充率對鋁氨溝槽熱管熱傳性能之影響

title: 填充率對鋁氨溝槽熱管熱傳性能之影響 abstract: 隨著全球對高速與可靠的通訊需求快速成長，衛星的發射數量隨之增加，具距離地表500至2000公里的衛星稱為低軌衛星，低軌衛星工作包含通訊、遙測、導航、氣象以及科學探索和國防，在面相太陽時80 oC，而在背對太陽時溫度降至-40 oC。銅水熱管常用在衛星的熱管理，在-40 oC環境時銅水熱管裡面的水會隨之結凍，進而影響衛星內部的散熱使內部計算元件溫度上升導致運算速度降低。鋁氨熱管近年來常用於衛星在外太空的散熱元件，氨在-40 oC時是液態，所以此研究以設計鋁氨熱管於應用，從初步設計熱管內部結構，並測試不同氨填充率的熱傳性能。在冷凝溫度25 oC時，氨的填充率從46.4 %到8.2 %，在高填充率時，熱阻較大且鋁氨熱管的溫度分布相近，在填充率14.9 %且加熱量380 W時，熱傳性能最好，得到最低熱阻為0.052 (oC/W)。當填充率低於填充率14.9 %，鋁氨熱管蒸發段尾部溫度上升，熱阻開始增加，最大熱傳量減少。 ;With the global demand for high-speed and reliable communication rapidly increasing, the number of satellite launches has also risen significantly. Satellites operating at altitudes of approximately 500 to 2000 km above the Earth’s surface are classified as low Earth orbit (LEO) satellites. These satellites perform various functions, including communication, remote sensing, navigation, meteorology, scientific exploration, and national defense. During operation, when facing the sun, the satellite surface temperature can reach 80 °C, while on the shaded side it can drop to −40 °C.Copper–water heat pipes are commonly used in satellite thermal management systems; however, in environments as cold as −40 °C, the water inside may freeze, which degrades thermal performance and causes the internal components to overheat, reducing computational efficiency. In recent years, aluminum–ammonia heat pipes have been increasingly adopted for space applications, as ammonia remains in a liquid state at −40 °C, making it suitable for extreme low-temperature operation.At a condenser temperature of 25 °C, the ammonia filling ratio was varied from 46.4 % to 8.2 %. At higher filling ratios, the thermal resistance was larger, and the temperature distribution along the aluminum–ammonia heat pipe was relatively uniform. When the filling ratio was 14.9% and the heat input was 380 W, the heat pipe exhibited the best thermal performance, achieving the lowest thermal resistance of 0.052 (°C/W). When the filling ratio was lower than 14.9 %, the temperature at the end of the evaporator section increased, the thermal resistance began to rise, and the maximum heat transfer rate decreased.

高壓氫/氨/空氣燃氣於等流場雷諾數之層紊流燃燒速度量測及正規化分析;Measurement and Normalized Analysis of Laminar and Turbulent Flame Speeds of High-Pressure H₂/NH₃/Air Mixtures at Constant Flow Reynolds Number

title: 高壓氫/氨/空氣燃氣於等流場雷諾數之層紊流燃燒速度量測及正規化分析;Measurement and Normalized Analysis of Laminar and Turbulent Flame Speeds of High-Pressure H₂/NH₃/Air Mixtures at Constant Flow Reynolds Number abstract: 本論文於先前已建立之大型可產生近似等向性紊流場的十字型風扇擾動雙腔體燃燒器中進行實驗，使用體積比45%氫氣/55%氨氣和空氣預混燃氣並操作於當量比 = 0.8，研究目的在於探討固定流場雷諾數(ReT,flow= uLI/ , u為均方根紊流擾動速度、LI為紊流積分尺度、為運動黏滯係數)條件下，壓力變化對層流及紊流火焰速度的影響。由於先前本實驗室已對此問題進行過甲烷/空氣、合成氣/空氣混合燃氣的探討，且已知甲烷/空氣在 = 0.8時層流火焰速度(SL)約為26 cm/s，故盡量挑選在相同當量比SL與其相近的氫/氨/空氣混合比例(SL ≈ 29 cm/s)來進行比較。實驗結果顯示，在1-5 atm範圍內，所有測試的流場雷諾數條件(ReT,flow = 6700、9100、11600、14200)，紊流與層流火焰速度皆隨壓力升高而下降，其中層流火焰速度與壓力的關係為SL ~ p-0.4，而紊流火焰速度(ST)隨不同雷諾數則有不同下降幅度(ST ~ p-n, n = 0.48~0.61)。此ST ~ p-n的結果，與一般在固定u時，ST會隨壓力上升而上升相反，後者是因壓力上升，運動黏滯係數下降造成ReT,flow上升，並且火焰厚度會隨壓力增加而變薄，導致火焰不穩定性增強。另一方面，ST隨壓力下降的幅度均大於SL，因此ST/SL亦隨壓力升高而呈下降的趨勢。此趨勢在1-5 atm範圍內與甲烷/空氣混合燃氣略有差異，但與氫/一氧化碳/空氣混合燃氣則相符。針對此現象，本論文推測由於壓力升高時H自由基的三體終止反應H + O2 (+M) → HO2 (+M)會大幅加劇，加上紊流場的影響，因此當H自由基受壓力抑制而導致局部反應區活性下降，整體紊流火焰速度將同步受限，這使得在高壓條件下，紊流火焰速度的衰減程度大於層流火焰速度的變化。最後，本論文結合本實驗室先前相同混合燃氣已有數據，透過以下四個不同團隊所提出之一般通式進行正規化分析: (1) Chaudhuri et al. (2012)； ST,c̅=0.5/SL = 0.438(ReT,flame)0.5(R2 = 0.77)；(2) Shy et al. (2019)； ST,c̅=0.5/u′ = 0.37(DaLe-1)0.5(R2 = 0.99)；(3) Wang et al. (2020)； ST,c̅=0.5/ SL−1 = 0.178(ReT,flame Le-2)0.56(R2 = 0.77)；(4) Lhuillier et al. (2021)；(ST,c̅=0.5/SL)(1/Da) = 2.27Ka0.91(R2 = 0.97)，其中c̅為火焰平均傳遞變數(mean progress variable)，相關無因次參數定義如下: ReT,flame = (urms/SL)(〈R〉/L)、Da = (SL/urms)(LI/L)、Ka = (urms/SL)1.5(LI/L)-0.5， R2為coefficient of determination，而R2大於0.7，表示這些通式皆具有不錯的正規化擬合程度，其中又以Shy及Lhuillier團隊提出的通式有最佳的擬合程度。;In this study, experiments are conducted in a previously established large dual-chamber fan-stirred cruciform burner capable of generating a near-isotropic turbulence field. The mixture consists of 45% H₂/55% NH₃/air in volume percentages at an equivalence ratio of ϕ = 0.8. The objective is to investigate the effect of pressure on laminar and turbulent flame speeds under constant flow Reynolds number conditions (ReT,flow= u′LI/ν, where u′ is the root-mean-square turbulent velocity fluctuation, LI is the integral length scale of turbulence, and ν is the kinematic viscosity of reactants). Since previous studies in our laboratory have examined lean CH4/air and syngas/air mixtures, where the laminar flame speed (SL) of CH₄/air at ϕ = 0.8 is approximately 26 cm/s, the present study selects lean premixed 45% H₂/55% NH₃/air flame with a similar SL ≈ 29 cm/s for comparison. The results show that within 1-5 atm, both laminar and turbulent flame speeds decrease with increasing pressure for all tested ReT,flow values of 6700, 9100, 11600, 14200. The pressure dependences follow SL ~ p-0.4 and ST ~ p-n, where n ranges from 0.48 to 0.61 depending on ReT,flow. Such results are different from the conventional observations under constant u′ conditions, where ST increases with pressure due to the enhancement of flame instabilities through thinner flames and the concurrent increase in ReT,flow resulting from reduced kinematic viscosity. Moreover, the decrease in ST with pressure is more pronounced than that in SL, resulting in a decreasing ST/SL ratio as pressure increases. This trend differs slightly from that of CH₄/air but agrees well with H₂/CO/air mixtures. To account for this phenomenon, this study proposes that under high-pressure conditions, the enhanced three-body termination reaction H+ O2 (+M) → HO2 (+M) significantly reduces H-radical concentrations. This effect, when coupled with turbulence that limits the local reaction-zone activity, leads to a stronger decrease in ST than in SL. By incorporating our previous experimental data, these ST/SL data can be merged onto the following four general correlations proposed by (1) Chaudhuri et al. (2012), ST,c̅=0.5/SL = 0.438(ReT,flame)0.5 (R2 = 0.77) (2) Shy et al. (2019), ST,c̅=0.5/u′ = 0.37(DaLe-1)0.5(R2 = 0.99) (3) Wang et al. (2020), ST,c̅=0.5/ SL−1 = 0.178(ReT,flame Le-2)0.56(R2 = 0.77) (4) Lhuillier et al. (2021), (ST,c̅=0.5/SL)(1/Da) = 2.27Ka0.91(R2 = 0.97), where ReT,flame = (urms/SL)(〈R〉/δL), Da = (SL/urms)(LI/δL), and Ka = (urms/SL)1.5(LI/δL)-0.5. All correlations yield the coefficients of determination (R2) above 0.7, indicating reasonable fitting accuracy, where the correlations proposed by Shy et al. and Lhuillier et al. have the highest R2 values.

使用氮與氟共摻雜石墨烯作為雙功能陽極修飾層以提升鋰金屬電池性能;Enhancing Lithium Metal Battery Performance Using Nitrogen and Fluorine Co-Doped Graphene as a Dual-Functional Anode Modifier

title: 使用氮與氟共摻雜石墨烯作為雙功能陽極修飾層以提升鋰金屬電池性能;Enhancing Lithium Metal Battery Performance Using Nitrogen and Fluorine Co-Doped Graphene as a Dual-Functional Anode Modifier abstract: 因應全球暖化與科技進步的需求，開發具可持續性與高能量密度的儲能系統已成為關鍵課題。因此，鋰金屬電池(Lithium Metal Batteries, LMBs)因為具備極高的理論比容量(3860 mAh g⁻¹)以及最低電化學電位(-3.04 V vs. SHE)，被廣泛視為下一世代高能量密度儲能系統的理想負極材料。然而，實際應用上卻受到嚴重限制，面臨的挑戰包括枝晶鋰生成導致在沉積過程中容易刺穿隔膜，引發短路與熱失控以及界面不穩定使電解液與鋰金屬的副反應生成不均勻、低機械強度和低導鋰性的固態電解質界面(Solid Electrolyte Interphase, SEI)，導致庫倫效率(Coulombic Efficiency, CE)下降與循環壽命縮短。為了克服上述問題，過去研究提出人工固態電解質界面(Artificial Solid Electrolyte Interphase, ASEI)概念，以兼具高強度與高導鋰性的保護層來穩定界面。氟化鋰(LiF)因具備高機械強度(~58 GPa)與化學穩定性，被廣泛應用於抑制枝晶穿透與降低副反應，氮化鋰(Li3N)則具有高導鋰性(~10-3 S cm-1)，能促進鋰離子快速傳輸並引導均勻沉積，此外，氧化鋰(Li2O)在適中氧含量下生成比例較高，能提供穩定的導鋰通道並減少過多氧轉化成Li2CO3。石墨烯基材料因高比表面積與優異導電性，被視為理想的鋰沉積載體。傳統電極添加黏著劑與助導劑，但這些成分容易引發副反應，降低穩定性，而無黏著劑(Binder-Free)能抑制額外副反應之干擾，展現更高的界面穩定性與電子及離子傳輸效率。本研究利用電泳沉積法(Electrophoretic Deposition, EPD)將氟化電化學剝離石墨烯(FG)與電化學剝離石墨烯(ECG)沉積於銅基底，製備Binder-Free電極，透過不同電漿處理引入氟氮雙功能，探討氧含量與氟氮比例對ASEI的影響。結果顯示，高氮含量促進Li3N的生成，降低成核過電位至62 mV，並於橫截面觀察到鋰沉積深度達4.25 μm，顯示其能有效改善導鋰性，高氟含量則促進LiF的形成，在循環257次時仍能維持93.8 % 的CE，證實其優異的機械支撐性與化學穩定性，而適中氧含量則生成更多Li2O，提供額外導鋰通道並提升界面穩定性。此外，退火處理進一步修復缺陷並強化碳結構，顯著延長循環壽命，證明透過合理調控氟、氮與氧，可設計兼具高穩定性與高導鋰性的ASEI。 ;In response to the urgent demand for sustainable and high–energy-density storage systems driven by global warming and technological advancement, lithium metal batteries (LMBs) have emerged as one of the most promising candidates for next-generation energy storage. Benefiting from an ultrahigh theoretical specific capacity (3860 mAh g-1) and the lowest electrochemical potential (-3.04 V vs. SHE), lithium metal is regarded as an ideal anode material. However, its practical application is severely hindered by the formation of lithium dendrites, which can penetrate the separator and cause short circuits and thermal runaway. In addition, unstable interfacial reactions between the electrolyte and lithium metal lead to the formation of a heterogeneous solid electrolyte interphase (SEI) with low mechanical strength and poor ionic conductivity, resulting in reduced Coulombic efficiency (CE) and shortened cycle life. To overcome these issues, the concept of an artificial solid electrolyte interphase (ASEI) has been proposed, aiming to design protective layers with both high mechanical robustness and excellent Li-ion conductivity. Lithium fluoride (LiF), with a high mechanical modulus (~58 GPa) and chemical stability, has been widely used to suppress dendrite penetration and mitigate side reactions. Lithium nitride (Li3N), featuring high ionic conductivity (~10-3 S cm-1), facilitates rapid Li-ion transport and promotes uniform deposition. Furthermore, lithium oxide (Li2O), when formed under moderate oxygen content, provides stable Li-ion diffusion channels while preventing excess oxygen from transforming into Li2CO3, thereby enhancing interfacial stability. Graphene-based materials, owing to their high surface area and excellent electronic conductivity, are considered ideal hosts for Li deposition. In contrast, traditional electrodes require the use of binders and conductive additives, which often introduce additional side reactions and degrade interfacial stability. Binder-free electrodes can eliminate such inactive components and interference, thereby exhibiting higher interfacial integrity and improved electronic/ionic transport efficiency. In this work, fluorinated electrochemically exfoliated graphene(FG) and electrochemically exfoliated graphene (ECG) were deposited on Cu foils using electrophoretic deposition (EPD) to fabricate binder-free electrodes. By applying different plasma treatments, dual-functional graphene containing both fluorine and nitrogen was constructed, and the effects of oxygen content and F/N ratio on ASEI performance were systematically investigated. The results demonstrate that high nitrogen content promotes Li3N formation, reducing the nucleation overpotential to 62 mV and enabling lithium deposition at greater depths (4.25 μm), thereby improving ionic transport. High fluorine content facilitates the formation of LiF, maintaining a CE of 93.8 % after 257 cycles and providing excellent mechanical and chemical stability. Meanwhile, moderate oxygen content enhances the generation of Li2O, which further stabilizes the interface and promotes Li-ion diffusion. The optimized electrode achieved over 450 hours of stable cycling with CE above 93 %. Moreover, annealing treatment effectively repaired structural defects and reinforced the carbon framework, significantly extending cycle life. These findings confirm the complementary roles of LiF, Li3N, and Li2O within ASEI and highlight that rational tuning of fluorine, nitrogen, and oxygen contents, combined with defect-healing annealing strategies, can yield a stable artificial interphase with both high mechanical strength and ionic conductivity. This work provides new insights into designing advanced ASEIs for high–energy-density lithium metal batteries.

高功率AI伺服器兩相蒸發冷卻系統研究;Development of Two-Phase Evaporation Cooling System for High Performance Ai Servers

title: 高功率AI伺服器兩相蒸發冷卻系統研究;Development of Two-Phase Evaporation Cooling System for High Performance Ai Servers abstract: 本計畫結合全球主要伺服器製造商美超微公司，以及國內最大熱交換器製造商高力公司，設計兩相蒸發冷板以及其相對應冷媒管路配置，解決此高功率晶片及其相對應伺服器之散熱問題。將協助國內相關業者持續保持技術領先國際，成為我國另一個兆元產業。另外由於高性能冷卻系統的開發，將有效提升資料中心能源使用效率，減少資料中心耗能，舒緩我國電力供應問題。