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熱虹吸管電池散熱模組研究
http://ir.lib.ncu.edu.tw/handle/987654321/93688
title: 熱虹吸管電池散熱模組研究 abstract: 隨著環保意識的抬頭,再生能源將成為未來最主要的能量獲取來源之 一。 再生能源並非可以隨時取得,因此可以利用儲能系統來儲存能量, 鋰 離子電池儲能系統因而被廣泛使用。然而, 由於快速充放電的需求, 鋰離 子電池在快速放電時所產生的熱增加, 因此如何對鋰離子電池模組進行熱 管理是一個非常重要的議題。
在現今的冷卻方式中, 直接氣冷成本最低。然而其最大的問題在於其 流道複雜,電池模組壓降較大,需要更多耗能來散熱。本研究利用將熱虹 吸管插入電池模組中,將模組內的熱導出,降低直接氣冷之壓降。
根據實驗結果在風速 1.97m/s 時, 直接氣冷模組可以在 9C 放電時控制 在 60°C 以下, 而鰭管模組可以在 11C 放電時控制在 60°C 以下, 增加 1.2 倍,且使用鰭管之壓降相比於直接氣冷模組小約 6.5 倍。
使用鰭管模組風 扇僅需要 30.5Hz 就可解決 9C 放電時的熱,直接氣冷模組則需要 59.5Hz, 因此使用鰭管模組可減少因散熱所需的耗能。;With the rise of environmental awareness, renewable energy will become one of the primary sources of energy in the future. Since renewable energy is not always available, energy storage systems play a crucial role in storing energy. Lithium-ion battery energy storage systems are widely utilized for this purpose. However, due to the demand for fast charging and discharging, the increased heat generated during fast discharging in lithium-ion batteries has made thermal management of lithium-ion battery modules a critical issue.
Among the current cooling methods, direct air cooling has the lowest cost. However, its main issue in the complexity of its flow channels, resulting in a larger pressure drop in the battery module and requiring more energy consumption for heat dissipation. In this study, we insert thermosiphon into the battery module to export the heat inside the battery module, reducing the pressure drop associated with air cooling.
Based on the experimental results, at a frontal air velocity of 1.97m/s, the direct air cooling module can maintain temperature below 60°C during 9C discharge, while the finned-tube module can achieve the same below 60°C during 11C discharge, increase of 1.2 times. When using the finned-tube module, the fan only needs 30.5Hz to dissipate heat during 9C discharge, the direct air cooling module requires 59.5Hz. Therefore, using the finned-tube module can reduce the energy consumption required for heat dissipation.
<br>微多孔表面漸擴微流道蒸發器性能研究
http://ir.lib.ncu.edu.tw/handle/987654321/93687
title: 微多孔表面漸擴微流道蒸發器性能研究 abstract: 為了解決未來電子元件的高發熱量,本研究將微多孔表面應用到雙通漸擴微流道蒸發器上,來得到高性能的蒸發器。並與其他種蒸發器作比較,包含微多孔表面的雙通直線與單通直線微流道蒸發器,以及平滑表面的單通直線微流道蒸發器。微多孔表面由平均粉末大小16 μm的鋁粉膠黏堆疊於流道表面上平均厚度約為 50 μm。
雙通漸擴微流道蒸發器中,相較於平滑表面,微多孔表面因為增加成核孔洞的密度,增強成核沸騰,熱傳性能 較高,但因為較多的汽泡生成,流道容易堵住,使壓降一併上升,在流量100與187 ml/min,燒乾會發生在較低的加熱通率。微多孔表面能對其熱傳效果提升16% ~ 54%,同時壓降亦增加30% ~ 40%。
在雙通流道形式中,相較於直線流道漸擴流道因為第一通的尺寸較小,汽泡更易堵住,造成微多孔表面的漸擴 流道性能比直線差 。
另外將雙通與單通作比較,單通直線流道因為長度比較短所以汽泡
較不容易堵住,使性 能優於雙通的。
實際應用上,若欲用微多孔表面作增強,則可直接施加於單通直線流道上。若管路位置受限,須將入出口設置於同一側,可考慮使用多孔表面的雙通直線流道。;This study applies microporous surface on the two-pass divergent microchannel evaporator to obtain a high performance evaporator for solving high heat dissipation rate electronic devices in near future. The result will be compared with other evaporators, which includes single-pass and two-pass straight microchannel evaporator with microporous surface and single-pass straight microchannel evaporator with plain surface, developed by our lab. The 16 μm average size of aluminum particle is used to make the microporous surface, the average thickness is about 50 μm.
Microporous surface increases the nucleation site density, which enhances nucleate boiling and more bubbles are nucleated. While huge amount of bubble will block the channel easier, which causes the higher pressure drop and performance start decreasing at lower heat flux rate. For two-pass divergent microchannel evaporator, the heat transfer coefficient is increased 16% ~ 54% and the pressure drop is increased 30% ~ 40% when microporous surface is applied.
Comparison in two-pass channel shows that the heat transfer performance of divergent channel is worse than straight one due to the smaller size of first pass channel which will make the blockage of bubble easier. While comparing two-pass channel to single pass one, the latter one shows the better performance because of the shorter channel length.
In practice, apply microporous on single pass straight channel will yield the best performance compared to two-pass divergent and straight channel. Yet, if the inlet and outlet port are constrained to the same side, then two-pass straight channel with microporous surface will be a choice.
<br>Gioia 和 Chakraborty 紊流摩擦係數模型之研究;The Study of Gioia & Chakraborty’s Model for the Turbulent Friction Factor
http://ir.lib.ncu.edu.tw/handle/987654321/93686
title: Gioia 和 Chakraborty 紊流摩擦係數模型之研究;The Study of Gioia & Chakraborty’s Model for the Turbulent Friction Factor abstract: 本研究探討由Gioia和Chakraborty提出的紊流摩擦係數的理論模型(GC模型)。GC模型研究了在粗糙管道中的紊流摩擦係數,展示了該係數與雷諾數和管壁相對粗糙度的相關性。本研究主要介紹了GC模型使用的紊流現象理論。在固定粗糙度條件下變化模型參數,以觀察參數對摩擦阻力係數的影響,希望藉此學習紊流摩擦係數的物理意義。;This paper discusses theoretical model of the turbulent friction factor proposed by Gioia and Chakraborty (GC model). The GC model studies the friction factor in turbulent rough pipes, showing its dependence. On the Reynolds number and the relative roughness of the pipe wall. The study here introduces briefly the phenomenological theory of turbulence used by the GC model. The model parameters are varied under a fixed roughness condition to observe the influence of a parameter on the friction factor, hoping to gain physical understanding of turbulent friction.
<br>應用新型齒廓修整方法改善擺線針輪行星齒輪傳動的負載接觸特性;Improvement of Loaded Contact Characteristics of Cycloid Planetary Gear Drives by Applying a Novel Tooth Profile Modification Method
http://ir.lib.ncu.edu.tw/handle/987654321/93684
title: 應用新型齒廓修整方法改善擺線針輪行星齒輪傳動的負載接觸特性;Improvement of Loaded Contact Characteristics of Cycloid Planetary Gear Drives by Applying a Novel Tooth Profile Modification Method abstract: 擺線針輪行星齒輪機構因具有高減速比、高嚙合齒數,以及高承載與高衝擊吸收能力等優點,在各產業應用甚廣。在實際應用中,擺線齒輪作為此機構主要元件,擺線齒輪的齒形為研究的發展重點。因擺線齒輪與其他元件受到加工與組裝誤差等影響,使得擺線齒輪與針輪齒對接觸必須存在背隙,始得以補償誤差。一般而言,擺線齒輪之齒廓多採取修形方式來決定齒間背隙。另一方面,由於擺線針輪行星機構在實際傳動時,曲軸軸承必須存在間隙。而軸承間隙的存在也會影響到擺線齒廓與針齒的接觸,使得修形齒廓在設計上更加複雜。然而傳統以移距/等距方法的修整齒廓,會受限於有限數目的的參數,在給定背隙的限制條件下,並不易達成較佳傳動效能。本論文則提出一種新的齒廓修整方式,來改善擺線針輪行星齒輪機構在具有齒廓背隙與曲軸軸承間隙狀況下,各接觸對間的負載狀況;特別是雙齒差擺線齒對在在齒頂處的接觸衝擊問題。本文所提出的齒廓修整方法有別於傳統移距/等距方法,係直接由預定單一擺線齒與針齒嚙合的曲軸轉動角度誤差關係,來設計擺線齒廓。此一方法可以直接將要求背隙納入轉動角度誤差曲線設計之中,並且透過改變此誤差曲線參數來改變各接觸對的受力關係,以滿足傳動需求。由這種修整方式所得到擺線齒廓,也適合使用目前CNC齒輪精加工的成熟技術來製作。本研究曲軸轉動角度誤差曲線係選用對數曲線,並使用考量軸承間隙下的受載接觸分析模型做為分析工具。首先透過有系統分析新型齒廓修整參數對傳動效能的影響,建立參數設計法則。並以此對新式修整方法與傳統等距/移距修整方法所得到的齒廓進行案例分析與比較。分析結果顯示,新型修整的齒廓案例具以下優勢:在單齒差擺線齒輪方面,可以有效提高接觸率,降低各個接觸對最大負載值。在雙齒差擺線齒輪方面,滾子或爪銷接觸對受力無明顯差異,但在擺線/針齒接觸對有較佳受力表現;同時在具有軸承間隙下,齒對接觸範圍可以有效避開齒頂位置,降低了軸承間隙對齒頂撞擊接觸的風險。由研究結果顯示,本論文所提出之新型齒廓修整方式,可以根據設計要求,如背隙、受力大小、傳動誤差等,有系統地調整參數,有效改善擺線針輪行星減速機的傳動性能。
;The cycloid pin-wheel reducer is widely used in various industrial application due to high reduction ratio, large number of engaged tooth pairs, as well as high load capacity and shock absorption ability. In practical applications, the profile of the cycloidal gear, which is the critical component of this mechanism, is the focus of research and development. Because the cycloidal gear and the relevant components are affected by manufacturing and assembly errors, backlash between the contact tooth pairs must be present to compensate these errors. In general, the backlash can be achieved by using profile modification of the cycloidal tooth. However, due to the transmission of a cycloidal-pinwheel planetary mechanism, a clearance must exist in the crankshaft bearing. This clearance also affects the contact between the cycloidal tooth profile and the pin, making the profile design more complex. However, the conventional method of profile modification using the shifting-offset/equidistant-offset modification is limited by a finite number of parameters and does not easily achieve improved transmission while adhering to a given backlash constraint.
This thesis proposes a novel method for tooth profiles modification to enhance the loaded contact characteristics of contact pairs in a cycloidal-pin wheel planetary gear mechanism. The method addresses the issue of backlash in the tooth profile and clearance of the crankshaft bearings, with a focus on the contact impact of the tooth pairs at the tip of the cycloidal in the gear mechanism with tooth number difference of two. The tooth profile modification method proposed in this paper is based on designing a cycloidal tooth profile from the predetermined rotation angle error curve of the crankshaft for the mesh of a cycloid and a pin tooth. This method differs from the conventional shifting-offset/equidistant-offset modification method. This method incorporates the required backlash directly into the design of the rotation angle error curve. By adjusting the parameters of this error curve, the force relationship between the contact pairs can be changed to meet the transmission requirements. The cycloidal tooth profile obtained by this modification method is also suitable for manufacturing using current CNC gear finishing technology.
In this study, the logarithmic curves were used to represent the rotation angle error curves of the crankshaft. The analysis tool used was the loaded contact analysis model with consideration of crankshaft bearing clearances. The influence of the profile modification parameters on the transmission performance was systematically analyzed, and the parameter design rules were also established. A case study was conducted to compare the profiles obtained by the novel profile modification method with those obtained by the conventional method. The analysis results demonstrate the advantages of the modified profile using the proposed method: (a) It is possible to effectively increase the loaded contact ratio and reduce the maximum load value for each contact pair in the case of the cycloidal gear mechanism with a tooth number difference of one. (b) For the cycloidal gear mechanism with a tooth number difference of two, there is no significant difference in the force on the contact pairs of the bearing rollers or the pin shaft with the cycloidal gear. However, there is better force performance on the cycloidal-pin tooth contact pairs. Additionally, when there is bearing clearance, the contact area of the tooth pairs can effectively avoid the position of the tooth tips, reducing the risk of contact impact on the tooth tip due to the bearing clearance.
The study demonstrates that the proposed tooth profile modification method can systematically adjust parameters to meet design requirements, such as backlash, forces acting on the contact pairs, and transmission error, resulting in improved transmission performance of the cycloid planetary gear reducer.
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