外加磁場作用下具磁性奈米流體之脈衝式熱管熱傳性能研究

Study on the heat transfer performance of a pulsating heat pipe filled with magnetic nanofluids under an applied magnetic field

鍾佳瑋(CHIA-WEI CHUNG)

指導教授 ： 翁輝竹

中原大學/工學院/機械工程學系/碩士(2022年)

https://doi.org/10.6840/cycu202201554

摘要

本論文完成外加磁場作用下具磁性奈米流體之脈衝式熱管熱傳性能之研究，主要目的是透過實驗的方式，探討在不同輸入熱功率下，填充磁性奈米流體的脈衝式熱管在磁場作用下的熱傳性能；本研究首先利用化學共沉法及溶膠凝膠法製備出實驗所需之水基奈米流體，磁流體體積分率分別為0.5 %、1.5%、2.5%，熱管本身使用內徑2.2 mm的毛細銅管塑形而成，並且連接三通閥，完成熱管本身製作，接著將熱管抽真空至工作壓力135 mmHg，並且利用四通閥填充工作流體。在完成熱管本身製作後設計整體實驗系統，冷凝段選用鋁材加工，蒸發段選用熱傳導係數較佳的紅銅當作加熱媒介；實驗過程中冷凝段溫度控制在25oC，蒸發段熱源使用電源供應器，將輸入熱功率控制在15 W至65 W的區間，等待各點溫度達到穩定後紀錄並計算熱阻值；實驗中使用強力永久磁鐵於蒸發段及冷凝段加入非均勻磁場，並且觀測磁場對於整體熱傳效能的影響。
結果發現，使用磁性奈米流體做為工作流體，其最低熱阻值出現在φ=1.5%冷凝段架設磁場的情況下，比起純水下降約46.15%；而並非是濃度越高熱傳效果越佳，四個不同濃度的案例中體積分率φ=1.5%熱傳性能最佳，在輸入熱功率為65 W時熱阻值為0.4 ℃/W；在不同磁場架設位置的實驗結果發現，有加入磁場熱管熱傳性能皆會提升，其中磁場架設在冷凝端的效果又相對磁場架設在蒸發段效果較佳，在體積分率φ=1.5%輸入熱功率為45 W且磁場設置於冷凝段時，與純水的案例相比降低了51.92%的熱阻值；最後在磁場梯度效應的實驗中發現，在本次研究的範圍中，非均勻磁場梯度越強，對於熱傳性能影響越好。

關鍵字

脈衝式熱管 ； 鐵磁流體 ； 水基奈米磁流體 ； 非均勻磁場

並列摘要

This thesis has been completed for the study on the heat transfer performance of a pulsating heat pipe filled with magnetic nanofluids under an applied magnetic field. In this study, water-based nanofluids were first prepared by the chemical coprecipitation method and sol-gel method. The volume fractions of prepared magnetic nano fluids were 0.5%、1.5% and 2.5%. The capillary copper tube with a diameter of 2.2 mm was molded and connected with a three-way valve to complete the heat pipe. Then, the heat pipe was evacuated to a working pressure of 135 mmHg, and the four-way valve was used to fill a working fluid. The condensation section was made of aluminum, and the evaporation section was made of red copper, due to its better thermal conductivity. During the experiment, the temperature of the condensation section was controlled at 25oC, and in the heat source of the evaporation section, a power supply was used to control the heat input within the range of 15 W to 65 W. When the temperature of each location reaches steady state, the data can then be recorded and input to the formula to calculate the thermal resistance value. In the experiments, a strong permanent magnet was used to add a non-uniform magnetic field. The effect of the magnetic field on the overall thermal resistance and heat transfer performancecan then be further evaluated.
Experiment results showed that when using a magnetic nanofluid as the working fluid, the best heat transfer efficiency is about 46.15% higher than deionized water. It was also found that the higher the concentration doesn’t offer better heat transfer. In the four cases with different concentrations, the one with volume fraction φ =1.5% has the best heat transfer performance, and the thermal resistance value is 0.4 ℃/W when the input heat is 65 W. The experimental results at different magnetic field erection positions show that the heat transfer performance of the heat pipe with the addition of a magnetic field is improved. The effect of the magnetic field installed near the condensation section provides better performance than that installed near the evaporation section. In the best case, the heat transfer performance is increased by 51.92% compared with the case without the magnetic field. Finally, in the experiment on the magnetic field gradient effect, it is found that within the scope of this research, the stronger the non-uniform magnetic field strength, the better the effect is on heat transfer performance.

並列關鍵字

pulsating heat pipe ； water-based magnetic nanofluid ； non-uniform magnetic field ； magnetic field gradient

參考文獻

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