沸騰雙相流譜與微型甲醇重組產氫裝置效能

Boiling Two-phase Flow Pattern and It's Effect on The Performance of An Integrated Micro Methanol Reformer

李承峰(Cheng-Fong Lee)

指導教授 ： 潘欽 ； 裴晉哲

國立清華大學/原子科學院/工程與系統科學系/碩士(2014年)

https://doi.org/10.6843/NTHU.2014.00306

摘要

本研究針對重組式甲醇燃料電池(RMFC)的前端氫氣來源設計一微型產氫裝置。此微型產氫裝置之研究目的為將微流道熱交換器(MCHE)與微流道觸媒重組器(MCR)利用微機電加工技術(MEMS)製作並完成整合。希望透過有效的整合能將觸媒進行POM化學反應後產生的熱量經熱交換器傳至液態甲醇，以便提供液態甲醇沸騰所需的熱量；同時亦能將產出的高溫氫氣降至60~80℃以符合燃料電池之工作溫度。
經完成整合後之微型產氫裝置幾何尺寸為20×20×2.13〖mm〗^3(2.13mm為厚度)，其中熱交換器正、反兩面皆有蝕刻深200μm之微流道。此外，冷端流場利用漸擴式微流道的設計來抑制液態甲醇在沸騰時其蒸氣所產生的回衝，希望藉此提升進料穩定性。而觸媒重組器(由曾繁根老師實驗室提供)則是內含單面蝕刻深350μm之微流道，並且透過指叉型微流道之設計使甲醇蒸氣與氧氣能充分混合並均勻分散在觸媒重組器內，以提升觸媒產氫效能。另一方面，觸媒則是選定銅錳鋅奈米顆粒(由黃鈺軫老師實驗室提供)。
本研究於實驗方面量測進口溫度來判斷進料穩定性；以及透過高速攝影機和中子射線照相觀察流體之雙相流流動行為，彈狀流、環形流、反環形流、液滴流與乾化等五種流譜皆成功觀察到；最後利用氣相層析儀分析產氫結果。本研究並探討氧氣與甲醇當量比以及加熱功率對產氫結果之影響，其中，最高之氫氣選擇率可達77.4%。一系列完整之研究將於本文依序介紹。

關鍵字

雙相流 ； 微型甲醇重組器 ； 微型熱交換器

並列摘要

In this study, a micro heat exchange-type hydrogen supplier (MHEHS) was successfully demonstrated as a fuel supply source for micro reforming methanol fuel cell (RMFC). The purpose of this study is integrating the micro channel heat exchanger (MCHE) and the micro channel reformer (MCR) by using the technique of micro electromechanical system (MEMS). In terms of the adequate integration, we are able to reuse the heat generated by the POM reaction. The heat generated is conducted to the cold side of the MCHE, providing enough heat for liquid methanol to start boiling. Meanwhile, the extremely hot hydrogen produced by POM reaction could be cool down to 60~80℃ since it is the working temperature of fuel cell.
The geometric dimension of MHEHS is20×20×2.13mm^3, for which 2.13mm is the thickness. There are 18 micro channels with 240μm for both the hot side and the cold side of MCHE. In addition, it’s worth mentioning that the diverging micro channel is designed to suppress the back flow while boiling is occurring, and to improve and enhance the stability of two-phase flow. The MCR is a finger- type design with channel depth of 350μm, provided by the lab of Professor F.G.Tseng, and the depth of micro channel in MCR is350μm. The micro channel is designed to make oxygen mix with methanol steam and subsequently pass uniformly into the MCR. Consequently, the performance of producing hydrogen may be enhanced. Besides, the nanoparticle of Cu-Mn-Zn, developed and provided by the lab of Professor Y.T.Huang, is chosen to be the catalyst in MCR.
The temperature at the inlet is measured to judge the stability of transporting precursor. Moreover, the high speed camera and Neutron Radiography (NR) are employed to observe the two-phase flow pattern in MCHE. Slug flow, annular flow, film break-up, droplet flow and dry out have been successfully observed . Finally, Gas Chromatography (GC) is used to analyze the component of the product, especially hydrogen. On the other hand, the effects of methanol flow rate, oxygen flow rate and the performance of MHEHS are studied, in terms of methanol conversion ratio, hydrogen production selectivity and CO production selectivity. A hydrogen selectivity up to 77.4% is obtained under the condition of V_MeOH= 0.04 sccm; V_(O_2 )= 10 sccm; q=22.5W in this research.

並列關鍵字

two-phase flow ； micro methanol reformer ； micro heat exchanger

參考文獻

[9]. 黃文利, “氣體加熱叉流式微流道熱交換器之流動沸騰熱傳研究An Investigation of Flow Boiling Heat Transfer on Cross-flow Microchannel Heat Exchanger with Gas Heating”, 國立清華大學碩士論文,2012.

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