多噴嘴微流道晶片散熱器之噴嘴孔徑組合研究

A Study of Jet Diameter Combination of Micro Channel Impingement with Multiple Jets for Chip Cooling

廖紹宇(Shao-Yu Liao)

指導教授 ： 簡良翰

國立臺北科技大學/機電學院/能源與冷凍空調工程系碩士班/碩士(2012年)

摘要

考量現今電子運算晶片發熱量日益增高，故需要發展出一理想化之散熱系統，故本研究針對整合噴擊與微流道之混合性散熱機制，設計出噴嘴與微流道一體成型之散熱結構。於投影面積12×12mm2的散熱器中，建立流道高0.8mm，寬0.6mm，流道長度為12mm，共計11條微流道之加熱表面，每條微流道設置3個噴擊孔，孔徑為中心最大之孔徑0.54mm與兩側靠近微流道出口較小0.3mm之漸縮式孔徑排列組合，工作流體為FC-72，入口飽和溫度為25℃及50℃，並設定噴擊流量為100~710ml/min。進行實驗分析。結果發現，單相熱傳時熱傳性能皆會隨著噴擊流量增大而呈現線性上升之趨勢，由於本研究為漸縮式噴擊孔排列組合方式，有助於熱傳進入兩相沸騰熱傳，而當流量增至一定範圍以上時，流道內流速過快導致對流熱傳效應較沸騰兩相熱傳更為顯著。本研究另外於5-0.4-1.5加熱表面上裝設可視化石英加工玻璃，以拍攝微流道內兩相氣泡生成情形，發現在低流量(100ml/min)狀態下，加熱瓦數為2W時，即發現流道中已有微小的氣泡產生，推測本研究表面在不同流量測試下，可能皆提早進入兩相沸騰熱傳，並隨著加熱量的增加，使得流道中出現柱狀氣泡團的現象。為了有效驗證實驗與模擬本研究加熱表面之單相熱傳性能與壓損，故建立三排微流道與噴擊孔之幾何模型，結果顯示，熱傳性能實驗值會比模擬值還高，推測於實驗條件下，流道內可能已進入兩相熱傳，造成熱傳性能較佳的趨勢。此外，由於本研究所模擬散熱器模型僅三個流道，而實際散熱器有11個流道，導致流體流經於噴孔上方分配區時，造成流量分配不均的情形，並形成額外之分配區壓損，故模擬之壓損值較小。經由迴歸及疊代計算，可歸納出單相熱傳經驗式，其誤差範圍為±16%以內。

關鍵字

噴擊冷卻 ； 微流道 ； 單相熱傳 ； 兩相熱傳 ； 流場可視化

並列摘要

As chip power heat in electronic equipment has been increasing, an effective cooling system is required for computer chips. In this study, a heat sink integrating micro-channels with multiple jets was designed for chip cooling. This study used dielectric fluid FC-72 as working fluid. The cooling fluid was introduced to a 12×12mm2 heated surface, which had 11 micro-channels, each channel was 0.8 mm high, 0.6 mm wide, and 12 mm in length. There were 3 nozzles installed on each micro-channel. The nozzle diameters combination were decreasing from center of each channel to two sides of channel’s outlets, and the diameters varied from 0.54mm to 0.3mm. In the tests, the saturation temperature of cooling device system was set at 25 and 30℃, and the volume flow rate varied from 100 to 710 ml/min.
The experimental results showed that heat transfer performance increased with increasing flow rate for single phase heat transfer, and in two phase heat transfer regime, due to this study is explored decreasing nozzle diameters combination, which caused flow velocity too fast in channels with higher flow rates, so, the effects of convection heat transfer was much more than the effects of the boiling heat transfer. Additionally, in order to capture two phase flow behavior along the channels, the 5-0.4-1.5 test module was replaced a minimized quartz glasses for flow visualization. It showed a combination bubbly flow phenomenon in channel with low volume flow rate(100ml/min) while the heat wattage was 2 watts. Hence, we speculated that test in different volume flow rates on test module, the all heat transfer type perhaps early turn to two-phase boiling heat transfer, even with increasing heat caused further bubble coalescence into longer columnar bubbles in channel. Besides, a unit cell of the hybrid configuration that was used in the single phase computational simulation for validating the heat transfer performance and pressure drop with experimental results. The unit cell consists of three of the eleven micro-channels and nozzles with surrounding solid. The results showed that heat transfer performance in experiments was higher than in simulation, which was predicted that heat transfer type perhaps early turn to two phase boiling heat transfer in channels under experimental condition. And due to simulation geometry simply 3 channels differed to practical test module with 11 channels, while the working fluid into the top of nozzle’s separating zone, which was caused the volume flow rate in uneven distribution so that produce an eatra pressure drop in separating zone, that’s why pressure drop smaller in simulation. Correlation of heat transfer coefficient of the single-phase heat transfer of the micro-channel/jet cooling integrated device has been developed. Compared with the single phase data, the prediction uncertainties is within ±16%.

並列關鍵字

Jet cooling ； Micro Channels ； Single Phase Heat Transfer ； Two Phase Heat Transfer ； Flow Visualization

參考文獻

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[23] 張秦耀、簡良翰，「非導電流體之兩相噴擊冷卻實驗研究」，碩士論文，國立臺北科技大學能源系，台北，2009。

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