小波分解方法分辨出跨越2到3個(gè)時(shí)間尺度的針肋型微通道沸騰傳熱機(jī)理
發(fā)布時(shí)間：2018-11-08 15:30
【摘要】：微小型化是當(dāng)代科技發(fā)展的重要方向之一。隨著時(shí)代發(fā)展,空間、信息及生物等高新技術(shù)領(lǐng)域亟待解決超小面積、超高熱流密度條件下的換熱問(wèn)題。在這一背景下,本文針對(duì)微流體在硅基微通道內(nèi)的流動(dòng)沸騰波動(dòng)特性進(jìn)行了創(chuàng)新性的實(shí)驗(yàn)研究。本研究采用微電子機(jī)械系統(tǒng)(MEMS)加工工藝,設(shè)計(jì)并加工了一種具有微針肋結(jié)構(gòu)的硅基微通道芯片,設(shè)計(jì)并搭建了微流體閉式循環(huán)回路系統(tǒng)和微流體光學(xué)平臺(tái),建成了高速的、高空間分辨率的、高精度的、時(shí)鐘同步的流體傳熱和可視化數(shù)據(jù)采集系統(tǒng)。采用去離子水為工質(zhì),進(jìn)行了單相水校核實(shí)驗(yàn)和氣液兩相流動(dòng)沸騰實(shí)驗(yàn)。微通道中的流動(dòng)沸騰特性受流量、熱流密度、通道結(jié)構(gòu),入口溫度等各參數(shù)的影響,由44個(gè)工況歸納出三類流動(dòng)沸騰不穩(wěn)定區(qū)間：當(dāng)q/G 0.62 kJ/kg時(shí),微通道內(nèi)沸騰初始,呈現(xiàn)準(zhǔn)穩(wěn)定沸騰模式；當(dāng)0.62 kJ/kg q/G 1.13 kJ/kg時(shí),微通道內(nèi)出現(xiàn)自維持的周期性沸騰模式,進(jìn)出口壓差和壁溫呈現(xiàn)周期10-15s的波動(dòng)；當(dāng)q/G1.13 kJ/kg時(shí),微通道內(nèi)沸騰劇烈,呈現(xiàn)準(zhǔn)穩(wěn)定沸騰模式。觀察到新的沸騰現(xiàn)象,如液島、錐形兩相沸騰發(fā)展區(qū)、兩種沸騰核化模式等。創(chuàng)新性地使用小波分析方法處理以上流動(dòng)沸騰的波動(dòng)信號(hào),明確分辨出這三類不穩(wěn)定流動(dòng)沸騰類型和機(jī)理：第一類沸騰不穩(wěn)定性為密度波不穩(wěn)定性與氣液流型轉(zhuǎn)換引起的不穩(wěn)定性耦合,包含兩個(gè)時(shí)間尺度；第二類沸騰不穩(wěn)定性為壓力降型不穩(wěn)定性、密度波不穩(wěn)定性以及氣液流型轉(zhuǎn)換引起的不穩(wěn)定性耦合,包含三個(gè)時(shí)間尺度；第三類沸騰不穩(wěn)定性為密度波不穩(wěn)定性與變速液膜蒸發(fā)引起的不穩(wěn)定性耦合,包含兩個(gè)時(shí)間尺度。溫度信號(hào)分析結(jié)果與可視化照片對(duì)應(yīng)良好,確切地解釋了毫秒級(jí)的沸騰現(xiàn)象和傳熱趨勢(shì)。在通道內(nèi)流動(dòng)傳熱實(shí)驗(yàn)研究領(lǐng)域,結(jié)合小波分析方法的對(duì)于毫秒級(jí)溫度信號(hào)波動(dòng)的分析和機(jī)理解釋,在國(guó)內(nèi)外文獻(xiàn)中尚無(wú)報(bào)道。
[Abstract]:Miniaturization is one of the most important directions in the development of modern science and technology. With the development of the times, the problem of heat transfer under the condition of ultra-small area and ultra-high heat flux is urgently needed to be solved in the field of space, information and biology. In this context, the flow boiling wave characteristics of microfluids in silicon-based microchannels have been investigated experimentally. In this study, a silicon microchannel chip with micro-needle rib structure was designed and fabricated by using microelectromechanical system (MEMS) process, and a micro-fluid closed loop system and a micro-fluid optical platform were designed and built, and a high-speed microfluidic microchannel chip was built. High spatial resolution, high precision, clock-synchronous fluid heat transfer and visual data acquisition system. Using deionized water as working medium, single phase water verification experiment and gas liquid two phase flow boiling experiment were carried out. The characteristics of flow boiling in microchannels are affected by flow rate, heat flux density, channel structure and inlet temperature. From 44 operating conditions, three types of flow boiling instability zones are concluded: when Q / G is 0.62 kJ/kg, The initial boiling in the microchannel shows a quasi-stable boiling mode. At 0.62 kJ/kg Q / G 1.13 kJ/kg, the self-sustaining periodic boiling mode appeared in the microchannel, and the pressure difference between inlet and outlet and the wall temperature fluctuated for 10-15 s. When q/G1.13 kJ/kg, the microchannel boiling is intense, showing a quasi-stable boiling mode. New boiling phenomena such as liquid island, conical two-phase boiling developing region and two boiling nucleation modes were observed. Innovative wavelet analysis is used to process the wave signals of the above flow boiling. The types and mechanisms of these three types of unstable flow boiling are clearly distinguished. The first type of boiling instability is the coupling of density wave instability and gas-liquid flow pattern transition, which includes two time scales; The second type of boiling instability is pressure drop instability, density wave instability and instability coupling caused by gas-liquid flow pattern conversion, which includes three time scales. The third type of boiling instability is the coupling of density wave instability and variable velocity liquid film evaporation, which includes two time scales. The results of temperature signal analysis correspond well with the visual photos, which explain exactly the boiling phenomenon and heat transfer trend in millisecond order. In the field of experimental study of flow heat transfer in channels, the analysis and mechanism explanation of millisecond temperature signal fluctuation based on wavelet analysis method have not been reported in the literature at home and abroad.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TK124
本文編號(hào)：2318897
[Abstract]:Miniaturization is one of the most important directions in the development of modern science and technology. With the development of the times, the problem of heat transfer under the condition of ultra-small area and ultra-high heat flux is urgently needed to be solved in the field of space, information and biology. In this context, the flow boiling wave characteristics of microfluids in silicon-based microchannels have been investigated experimentally. In this study, a silicon microchannel chip with micro-needle rib structure was designed and fabricated by using microelectromechanical system (MEMS) process, and a micro-fluid closed loop system and a micro-fluid optical platform were designed and built, and a high-speed microfluidic microchannel chip was built. High spatial resolution, high precision, clock-synchronous fluid heat transfer and visual data acquisition system. Using deionized water as working medium, single phase water verification experiment and gas liquid two phase flow boiling experiment were carried out. The characteristics of flow boiling in microchannels are affected by flow rate, heat flux density, channel structure and inlet temperature. From 44 operating conditions, three types of flow boiling instability zones are concluded: when Q / G is 0.62 kJ/kg, The initial boiling in the microchannel shows a quasi-stable boiling mode. At 0.62 kJ/kg Q / G 1.13 kJ/kg, the self-sustaining periodic boiling mode appeared in the microchannel, and the pressure difference between inlet and outlet and the wall temperature fluctuated for 10-15 s. When q/G1.13 kJ/kg, the microchannel boiling is intense, showing a quasi-stable boiling mode. New boiling phenomena such as liquid island, conical two-phase boiling developing region and two boiling nucleation modes were observed. Innovative wavelet analysis is used to process the wave signals of the above flow boiling. The types and mechanisms of these three types of unstable flow boiling are clearly distinguished. The first type of boiling instability is the coupling of density wave instability and gas-liquid flow pattern transition, which includes two time scales; The second type of boiling instability is pressure drop instability, density wave instability and instability coupling caused by gas-liquid flow pattern conversion, which includes three time scales. The third type of boiling instability is the coupling of density wave instability and variable velocity liquid film evaporation, which includes two time scales. The results of temperature signal analysis correspond well with the visual photos, which explain exactly the boiling phenomenon and heat transfer trend in millisecond order. In the field of experimental study of flow heat transfer in channels, the analysis and mechanism explanation of millisecond temperature signal fluctuation based on wavelet analysis method have not been reported in the literature at home and abroad.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TK124
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 馬友光;季喜燕;王東繼;付濤濤;朱春英;;矩形截面微通道內(nèi)氣-液兩相流壓力降的實(shí)驗(yàn)測(cè)定及關(guān)聯(lián)(英文)[J];Chinese Journal of Chemical Engineering;2010年06期
，本文編號(hào)：2318897
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