平面式二階段微熱電致冷器之脈衝致冷特性數值模擬;Numerical Analysis of Pulsed Cooling Performance on Two-stage Planar Thermoelectric Microcoolers

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Title:	平面式二階段微熱電致冷器之脈衝致冷特性數值模擬;Numerical Analysis of Pulsed Cooling Performance on Two-stage Planar Thermoelectric Microcoolers
Authors:	宋祐清;Sung, Yu-Ching
Contributors:	機械工程學系
Keywords:	微致冷器;二階段;熱電效應;脈衝過冷;micro-cooler;two-stage;thermoelectric effect;pulsed supecooling
Date:	2020-08-20
Issue Date:	2020-09-02 19:14:28 (UTC+8)
Publisher:	國立中央大學
Abstract:	隨著行動元件尺寸漸小，高功率輸出導致熱管理的困難，微熱電致冷器為極具潛力的解決方法。輸入穩定電流於垂直式熱電致冷器為研究大宗，也可用脈衝電流使溫度比穩態時更低，有利瞬態熱點冷卻。但較缺乏平面式微熱電致冷器施加脈衝之資訊量，故本文利用數值模擬軟體耦合多重物理場，使用熱擴散與電荷守恆方程並加入熱電效應，探討熱電模組配置影響單階段與二階段致冷器之過冷特性。首先確認穩態下致冷器能達到最大溫差的最佳穩態電流，再以此狀態輸入脈衝，分析過冷特性。穩態下，單階段致冷器熱電模組不影響致冷溫差，但材料面積增加，使致冷功率上升。爾後在單階段外跨接熱電模組形成兩階段致冷器，隨著第二階段材料增加，致冷溫差增加。施加脈衝之暫態分析下，單階段致冷器過冷溫度與維持時間都劣於二階段致冷器，但過衝溫度與回覆時間卻是相反，這是由於模組愈多造成的焦耳熱回流冷端影響。最後進行微致冷器於熱負載下的應用模擬分析，結果顯示穩定熱負載下使用脈衝致冷不如預期。但若是應用於瞬態熱點的冷卻能有效抑制熱點，避免加熱元件。上述本文模擬考慮於理想情況，未來可加入接觸阻抗與熱應力場分析其致冷性能之影響，並製作致冷器實驗輔以佐證。 ;As the size of mobile devices become smaller and high power output causes difficulties to thermal management, micro thermoelectric coolers(TEC) are a potential solution. The input of stable current to the vertical TEC is a major research project, and pulsed current can also be aimed at making the temperature lower than that in steady state, which is advantageous for transient hot spot cooling. However, there is a lack of information about current pulse applied on a planar TEC. Therefore, this paper uses numerical simulation and couple multiple physical fields. Thermal diffusion and charge conservation equations are solved and thermoelectric effects is considered to discuss the influence of thermoelectric module configuration on single and two-stage of supercooling characteristics of the cooler. First, we confirmed the optimum steady-state current about the maximum temperature difference which TEC can reached, and then input pulse current to TEC to analyze the supercooling. In steady state, TE modules in single-stage cooler don’t affect the cooling temperature difference, but cooling power. Afterwards, TE modules are connected after first stage to form a two-stage cooler. The more modules in the second stage is, the larger the cold side temperature difference is. Under the transient analysis, the supercooling temperature and holding time of the single-stage cooler are both inferior to the two-stage refrigerator, but the overshoot temperature and the recovery time are opposite. This is due to the joule heating of additional TE modules to lead more heat flux flow back to cold side. Finally, we simulate the micro-cooler under heat loading, and the results show that the pulsed cooling under stable heat loading is not as expected. But if it’s applied on the cooling of transient hot spots, it can effectively suppress the hot spots and avoid heating elements. The simulations in this article are based on ideal conditions. In the future, contact resistances and thermal stress fields can be added to analyze the influence of its cooling performance, and can be verified with the experiment of fabricating TECs
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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