DSpace collection: 博碩士論文

填充率對鋁氨溝槽熱管熱傳性能之影響

Fri, 06 Mar 2026 10:38:51 GMT

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

Fri, 06 Mar 2026 10:38:23 GMT

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

Fri, 06 Mar 2026 10:38:00 GMT

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.

以離散元素法建構添加熱壓鐵塊(HBI)的高爐爐喉佈料系統之研究

Fri, 17 Oct 2025 03:59:16 GMT

title: 以離散元素法建構添加熱壓鐵塊(HBI)的高爐爐喉佈料系統之研究 abstract: 本研究旨在以離散元素法 (DEM) 模擬高爐爐喉區域旋轉佈料行為，探討爐內各區域料層結構、粒徑分布、爐料分布特性以及孔隙率與礦焦比之變化，並建置縮小尺寸冷模實驗模型進行驗證，期望為高爐操作優化與減碳提供技術基礎。研究首先建製等比例縮小的高爐冷模裝置，選用黃豆與綠豆顆粒模擬焦炭與燒結礦，並量測其粒徑分布、密度、安息角、摩擦係數及恢復係數等物性，以確保數值模擬參數之真實性；再透過旋轉滑槽進行佈料實驗，獲得顆粒堆積輪廓與分布資料，作為數值比對依據。在模擬部分，本研究利用 EDEM 軟體建置旋轉滑槽模型，輸入參數進行佈料模擬。結果顯示，模擬與冷模實驗的顆粒分布與堆積輪廓接近，證實模型具備可靠性與準確性。進一步於全尺寸模型中，發現顆粒形狀模型的選用對料層結構合理性的影響顯著：僅以單球與雙球模型容易導致焦炭顆粒在中心區域產生不自然的平台結構，而引入三球模型後因具備更真實的幾何與滾動摩擦阻力，能有效抑制不合理滑動，使料層呈現穩定的 V 型分布。此外，不同模擬區域規模的測試也顯示，雖然縮小範圍能降低計算時間，但虛擬牆面會干擾顆粒流動並影響分布，需權衡效率與精度。在爐喉區域進行四層旋轉佈料後，結果顯示料層呈現典型的 V 字型結構，塊礦集中於外圍，燒結礦與 HBI 則沿著徑向均勻分布，而焦炭在中心區域的分布占比較高。在孔隙率方面，中心區域因大顆粒比例高而具較大空隙，因此孔隙率較高；中間區域則因小尺寸顆粒充填於孔隙中，導致孔隙率偏低、透氣性不足。礦焦比分析則顯示，外圍區域因塊礦比例較大而礦焦比較高，而中心區域則因焦炭占比高達約 70%，再加上卸料後期的大尺寸焦炭顆粒易滾入中心，造成礦焦比較低。綜合而言，本研究透過DEM 模擬，能分析高爐旋轉佈料行為與料層特性，並提供佈料操作的參考依據與孔隙率分布資料，可提升對高爐上部運行的理解與控制，為高爐煉鐵之減碳與效率改善奠定重要基礎。;This study aims to simulate the burden distribution behavior in the blast furnace throat using the Discrete Element Method (DEM), with a focus on analyzing the burden structure, particle size distribution, material distribution characteristics, and variations in porosity and coke-to-ore ratio across different regions of the furnace. A scaled-down cold model of the blast furnace was first constructed, in which soybeans and mung beans were selected to simulate coke and sinter, respectively. The particle size distribution, bulk density, angle of repose, friction coefficient, and restitution coefficient of the particles were measured to ensure realistic input parameters for numerical simulations. Burden distribution experiments were then conducted using a rotating chute to obtain particle bed profiles and distribution data for validation. In the simulation stage, a rotating chute model was established in the EDEM software, and the measured parameters were applied. The simulation results showed good agreement with the cold model experiments in terms of particle distribution and bed profiles, confirming the reliability and accuracy of the model. In the full-scale blast furnace model, the selection of particle shape representation was found to significantly affect the reasonableness of the burden structure: using only mono-sphere or bi-sphere models tended to produce an unnatural central coke platform, while incorporating a tri-sphere model provided a more realistic geometry and rolling resistance, effectively mitigating excessive coke sliding and forming a stable V-shaped burden profile. Further analysis of burden distribution via rotating chute simulation revealed distinct deposition behaviors among different burden types, including coke, sinter, lump ore, and hot briquetted iron (HBI). The results indicate that the burden bed exhibits a typical V-shaped profile, with lump ore mainly accumulating at the periphery, sinter and HBI distributed more uniformly along the radius, and coke predominantly concentrated in the central region. Porosity analysis showed higher porosity in the central zone due to the dominance of larger coke particles, while the intermediate region displayed lower porosity owing to the infiltration of smaller particles, leading to reduced permeability. The coke-to-ore ratio was higher at the periphery because of the greater proportion of lump ore, while the central region exhibited a lower ratio due to coke enrichment and the tendency of larger coke particles discharged later to roll toward the center. Overall, this study demonstrates that DEM simulation can effectively capture the rotating chute burden distribution and characterize the structural evolution of the burden layer. The results provide valuable insights and reference data for optimizing blast furnace charging operations and enhancing both efficiency and carbon reduction in ironmaking processes. Keywords: Rotating chute, Hot Briquetted Iron (HBI), Discrete Element Method, burden distribution.