Experimental Study on Two-Phase Flow in Microchannel Heat Sinks Using Binary Mixitures

本計畫擬以實驗方法探討以混合流體為工作流體時，微流道熱沈沸騰相變化之情形。擬使用之混合流體為流體/流體混合流體，以及奈米微粒懸浮流體(奈米流體)兩種。本計畫之主要目標為瞭解混合流體成份、流量、以及微流道幾何形狀等對微尺度相變化之影響。本計畫擬以量測流體流經微流道熱沉之壓降、熱傳係數，以及流場觀測等來達成上述之目標。The major goal of this two-year project is to investigate experimentally the boilingphenomena in microchannel heat sink using binary mixtures as working fluids. Two kinds ofmixtures, liquid-liquid and nanoparticle suspended fluid (nanofluids) will be used asworking fluids in this project. The objective of this project is to identify the effects ofmixture composition, flow rate, and microchannel geometries on the phase change inside themicorchannel. Measurements of pressure drop and heat transfer coefficient along with flowvisualization will be carried out to achieve this objective

Study on Single-Phase Microchannel Heat Sink Performance Enhancement

電子元件散熱為確保電子元件可正常操作及壽命必要之工作。隨著半導體技術發展日新月異，電子元件朝微小化及高功率發展，元件散熱更成為一具挑戰性之要求。在散熱裝置中，微流道熱沉為一可達到高散熱量之散熱裝置。尤其當沸騰熱傳使用於微流道熱沉(兩相微流道熱沉) 時，可達到之更高之散熱量。相較於使用單相工作流體之微流道熱沉(單相微流道熱沉)，利用兩相微流道熱沉有可使用之工作流體選擇性少、高壓降、以及複雜之流體操控條件等缺點。本計畫之目標，為開發具兩相微流道熱沉散熱能力之單相微流道熱沉，使微流道熱沉在實際應用上，更具便利性。為於單相微流道熱沉中達到高散熱量之效果，必須進行熱傳增益。本計畫延續上年度之計畫，擬於二年內，以實驗、數值模擬、及理論分析等三種方式進行傳統微流道熱沉熱傳增益方法。第一年為在微流道流體流向加入縱向聯通流道，使流場由原來之單向流場成轉成三度空間之流場，進而提升其熱傳係數。在第二年裡。我們擬將第一年之微流道設計，以奈米碳管形成之多孔微結構取代矽晶圓形成之微流道，其基本目標為利用奈米碳管高熱導特性及多孔結構特殊之熱傳增益效果，以進一步提升微流道熱沉之性能。在計畫完成後，我們預計完成散熱量可達200W/cm2 以上，壓降在50kPa 以內，以及元件溫度及壓降在容忍值範圍內之微流道熱沉

Experimental Study on Single-Phase Microchannel Heat Sink Performance Enhancement

電子元件散熱為確保電子元件可正常操作及壽命必要之工作。隨著半導體技術發展日新月異﹐電子元件朝微小化及高功率發展﹐元件散熱更成為一具挑戰性之要求。在散熱裝置中﹐微流道熱沉為一可達到高散熱量之散熱裝置。尤其當沸騰熱傳使用於微流道熱沉 (兩相微流道熱沉) 時﹐可達到之更高之散熱量。相較於使用單相工作流體之微流道熱沉 (單相微流道熱沉)﹐利用兩相微流道熱沉有可使用之工作流體選擇性少﹑高壓降﹑以及複雜之流體操控條件等缺點。本計畫之目標﹐為開發具兩相微流道熱沉散熱能力之單相微流道熱沉﹐使微流道熱沉在實際應用上﹐更具便利性。為於單相微流道熱沉中達到高散熱量之效果﹐必須進行熱傳增益。本計畫擬於三年內﹐以實驗進行三種熱傳增益方法之驗證及估算微流道熱沉性能之提升。第一年為使用流體分裂(flow disruption) 方式﹐其目標為驗證及估計傳統大尺度熱傳增益方法於微小尺度時之適用性﹐使用之微流道熱沉為矽質材料。在第二年裡。我們擬將第一年之微流道設計﹐以奈米碳管形成之多孔微結構取代矽晶圓形成之微流道﹐其基本目標為利用奈米碳管高熱導特性及多孔結構特殊之熱傳增益效果﹐以進一步提升微流道熱沉之性能。在第三年中﹐我們將探討結合流體分裂﹑高熱導多孔結構﹑及提升工作流體熱傳性質等三種機制之微流道熱沉性能改善。工作流體將由水改為奈米流體﹐以利用其改善熱導係數及熱擴散造成之熱傳增益效果。在計畫完成後﹐我們預計完成散熱量可達150W/cm2 ﹐元件溫度及壓降在容忍值範圍內之微流道熱沉

Design, Test, and Modeling of Microscale Redox Flow Battery

本計畫為結合微流道燃料電池(MFC)與液流電池(RFB)之優點製作一以釩電解液為反應物之微型電池。在此電池中液流電池之薄膜將以流體平行流動產生之界面取代，此係採取微流道燃料電池微流道燃料電池之優點。而釩電解液之循環流動則採自大型液流電池之設計。本計畫之主要目標為發展一微型、無薄膜、可充放電及自主運轉之電池，未來將可取代一般傳統之電化學電池。為達成預定之目標，本計畫擬進行實驗及理論之探討。在實驗方面，主要工作包括電池之製作及測試、電解液循環系統之設計及製作、以及晶片式電池主體及電解液循環系統之整合設計、製作及測試。為能達到最佳設計及深入了解電池運作機制，本計畫亦擬針對流道尺度、流量大小、電解液濃度、電解液循環幫浦機制、以及離子輸送等對電池效能之影響進行理論探討。The proposed project is motivated by combining the advantages of both microfluidic fuel cell(MFC) and redox flow battery (RFB) to construct a battery using vanadium electrolytes asreacting species. The proposed battery replaces the membrane in large-scale RFB by theinterface between the redox flow stream which is taken from the idea of MFC, while the reoxcouple circulation with pump and reservoirs are taken from the large-scale RFB. The overallobjective of this study is to develop a mircoscale, rechargeable, and self-actuated battery thatcould have the potential of replacing the conventional electrochemical batteries.To achieve this goal, both experimental and theoretical approaches will be carried out. Inexperiments, the tasks to be carried out include the construction and characterization of themembraneless RFB flow cell with externally connected pumping system, development andcharacterization of the on-chip pumping system aiming to provide the electrolyte circulationfor the microscale RFB, and integration of the microscale RFB cell and pumping system on asingle chip. To seek optimum design of the battery, effects of various parameters such aschannel size, flow rate, electrolyte concentration, pumping mechanism, and ion transport inthe system will be examined theoretically

Electrokinetic Effects in Micro/Nanoscale Membrane and Their Applications in Energy Conversion-Theory and Experiments

帶電膜在環境保護、生醫製程及能源轉換等工程及科學應用上，扮演相當重要之角色。而這些應用中膜孔隙之尺度大多屬於微奈米之範圍，因此對此尺度範圍流道中之電動效應進行基礎之探討，以了解電解液在此類流場中行為，對提升此些應用之效益，極為重要。本計畫之整體目標即擬針對微奈米尺度帶電膜之電動效應進行基礎之探討，並依據基礎探討之結果，應用於能源轉換之開發。本計畫擬定執行三年。第一年主要目標為建立微奈米尺度帶電膜之電動效應之數值模擬分析模式。數值模式將以連體力學之理論為基礎並結合微觀之效應，針對電解液濃度、孔隙大小、膜孔出入口以及膜孔表面電荷密度等對電力驅動及壓力驅動流場電動效應，進行詳細之分析。第二年之主要目標為對帶電膜之電動效應進行實驗量測。本研究將使用氫燃料電池中之離子交換膜Nafion 為材料，進行實驗。實驗結果除可用於驗證數值模式之正確性外，亦可藉由實驗結果分析Nafion 表面電荷密度及電位等特性。此外，藉由建立之實驗設備亦可應用於尋找其他可應用於燃料電池之替代離子交換膜以及水管理之探討。第三年之主要目標利用第一及第二年獲得之結果，進行應用電動效應於建立一能源轉換實驗。主要之目標為利用電動效應將壓力能轉換為電能，除建立實驗設備進行性能量測外，亦將利用非平衡熱力學結合微觀之效應進行性能分析。The overall objective of this project is to develop fundamental understanding of electrokineticeffects as electrolyte transporting through the charged membranes which are employed inmany engineering and scientific applications such as environmental projection, biologicalprocessing and energy conversion. Extensive studies have shown that charged membraneconsists of charged nanoscale pores. The present study will then focus on the electrokineticeffects in the nanoscale dimensions. Using the established understanding on theelectrochemical and electrokinetic characteristics, an electricity generation will also be built.The proposed project will be carried out in three phases over a period of three years. In thefirst year (the first phase), numerical model of electrokinetic effects in charged membranewith nanoscale pores will be developed for both electroosmotic-driven flow (EOF) andpressure-driven flow (EOF). It is aimed to gain the fundamental understandings in ionicconcentration distribution and electrical potential distribution in the charged membrane. Thenumerical simulation will be based on the continuum mechanics in corporation with themicroscopic effects. The effects of electrolyte concentration, pore surface charge density, poresize and pore entrance and exit on the fluid flow rate in EOF and the streaming potential inthe PDF will be analyzed in detail. In the second year (the second phase), experimentalmeasurement on flow rate in EOF and streaming potential in PDF will be performed. Thespecific membrane Nafion 117 used predominately in the proton exchange membrane fuel cell(PEMFC) will be employed as the charged membrane in the experimental measurement. It isaimed to verify the numerical models developed in the first year and gain more understandingon the electrokinetic effects in Nafion. Utilizing the measured results, the averaged chargedensity of Nafion, which has not been reported explicitly in the literature, can also bedetermined. The established experimental facilities can also be used in the future studyregarding the applications in the development of fuel cell, especially in the seeking ofalternate of Nafion membrane and water management. In the third year (the third phase), anenergy conversion unit producing electricity from the electrokinetic effects using the Nafionmembrane will be built and tested. A phenomenological model on the performance of thisenergy conversion unit based on nonequilibrium thermodynamics in cooperation withmicroscopic effects will also be conducted

Ionic Transport in Nanochannel with Concentration Gradient and Its Application in Power Generation

在過去大部分奈米流道離子傳輸的研究中，奈米流道兩側之電解液濃度皆相同，且皆假設奈米流道兩側連接於大儲槽。而在實際應用場合，奈米流道需連接至一定大小之流道或儲槽，且兩側之電解液可能具有濃度差異及流速。鑑於過去對此方面之研究較少，本研究擬針對此進行奈米流道離子傳輸特性進行實驗及理論探討。由於離子交換膜可視為奈米流道之組合，在實驗探討方面本研究擬利用離子交換膜替代奈米流道，探討之參數包括電解液之濃度比、流速、以及酸鹼值等對電流-電位曲線之影響。此外，電解液流動空間大小因影響濃度極化之邊界層厚度，故其對電流-電位曲線之影響，亦加以探討。在理論探討方面，則以單一奈米流道及連接之微米流道為物理模型，探討在流體流動、電遷移、分子擴散影響下，由計算所得之電流-電位曲線了解離子之傳輸特性，並與實驗結果驗證。當具有濃差之電解液直接接觸或以一離子交換膜分隔時，可建立一電位差，並可利用其建立一逆滲析發電裝置，其架構及原理與上述之奈米流道電流-電位曲線之反向操作。因此，本計畫擬將建立之實驗裝置及理論模式延伸至建立一以濃差為驅動力之發電裝置，並探討電解液之濃度比、流速、以及酸鹼值、流動空間大小，以及用以電子傳輸之氧化還原劑濃度等對發電效率之影響。Most of the previous studies on the ion transport through nanochannels focused on thesituation that nanochannel is connected with large reservoirs filled with electrolyte. The bulkconcentrations of the electrolyte are equal and motionless. In practical applications,nanochannel must be connected with finite-sized channel for flow supply. Under such case,the electrolytes on both ends of nanochannel may have different bulk concentration andvelocity. In the proposed project, we will focus on exploring more understanding on theeffects of concentration gradient and electrolyte flow on the ion transport through thenanochannel. The effects of electrolyte concentration ratio, flow velocity, pH value, and sizeof electrolyte compartment on the current-voltage curve will be examined both experimentallyand numerically to identify the ion transport characteristics. For the experiments, the ionexchange membrane will be employed to emulate the nanochannel array while single chargednanopore will be used in the physical domain.As the electrolytes with different concentrations are brought in contact or separated by ionexchange membrane, an electric potential is established. Based on the reverse electrodialysis,electricity can be harvested from this electric potential. The electricity generation based onreverse electrodialysis is the reversed operation as the current-voltage measurement describedabove. Therefore, the experimental setup and numerical model built will be extended toconstruct an electricity harvesting device based on reverse electrodialysis. The effects ofelectrolyte concentration ratio, flow velocity, pH value, size of electrolyte compartment, andconcentration of redox couples used for electron transport on the electricity generationefficiency will be examined both experimentally and numerically

具微流道散熱器的冰水裝置

一種具微流道散熱器的冰水裝置，其主要係於一容器本體設置有一致冷器，於致冷器上貼附設置有一散熱器，該散熱器主要係包含有一可供流體流入的入口部、一可供流體流出的出口部，以及密集設置於入口部與出口部間的微流道，並且各微流道係分別與入口部及出口部連通。藉此，散熱器可以利用眾多微流道形成密集式的大量散熱面積，不僅能夠提供致冷器運作時良好的散熱效果，並且大幅縮小散熱器及飲水設備之體積者

Investigation of Nonlinear Eelectrokinetic Eeffects in Integrated Micro-Nanofluidic Devices

The overall objective of this project is to develop fundamental understanding of nonlinearelectrokinetic effect in micro-nanofluidic devices driven by externally applied electric fieldand utilizing the understanding to construct a nanochannel-based fuel cell. The nonlinearelectrokinetic effect is primarily due to the ion enrichment and exclusion as the chargedchannel size is comparable with the Debye length. Although this effect has received muchattention recently, a comprehensive picture on the physical phenomena such as ionic currentvariation, induced pressure driven flow, and the induced electroosmotic flow is still neededsince it is essential for designing and fabricating micro-nanofluidic devices in variousapplications.The proposed project will be carried out within three years including theoretical analysis,numerical modeling and experiments. The tasks for each year are described as follows:First year: to establish theoretical analysis and numerical model that capable of exploring themore understanding on physical phenomena in a nanochannel including the microscopiceffects.Second year: to explore the nonlinear electrokinetic effect on the current rectification inbiological membranes and proton conductivity enhancement in proton exchange membranesin which the nanopores can virtually be viewed as assembly of nanochannels.Third year: to perform experiments to verify the theoretical and numerical models andconstruct a nanochannel-based fuel cell using nanocapillary array membrane.本計畫之主要目的為探討具有微尺度及奈米尺度之流體元件中非線性電動效應對流體流動及物質傳輸之影響。由於非線性電動效應於流體元件設計之重要性及應用之廣泛性，為近年來受矚目之研究課題，許多因此效應對奈米流道造成之影響如電流流動、誘導壓力產生之流體流動、離子電導、以及誘導電滲流場等仍須更進一步之探討。本計畫擬定執行三年。各年度之工作及目標為:第一年:建立電壓驅動之奈米尺度帶電流道中傳輸現象之理論分析及數值模擬模式。此理論分析及數值模擬模式將包括過去研究忽略的微觀效應。第二年:建立非線性電動效應對一具微米及奈米尺度之流體元件中之流體流動及離子分佈之數值模式，主要重點為探討非線性電動效應對電流增強及質子電導度增益之影響。第三年:以微奈米製造技術製作第一及第二年之物理模型，並進行實驗量測及理論與數值模式之驗證。此外，亦將根據前兩年之結果，設計及量測一利用奈米流道為質子交換之燃料電池