渦流管為安裝方便之小體積冷卻組件，不須使用冷媒及電源即可將壓縮空氣分離為冷與熱兩股氣流，因此適用於如機械加工之局部冷卻需求；本研究結合數值模擬、3D列印製作、幾何參數分析執行渦流管的冷卻性能優化，接著製作最佳化模型實體模型供測試，並量測驗證優化渦流管之性能。首先選定渦流管參考模型進行數值流場模擬，觀察其內部溫度與壓力分佈並計算其性能參數，包括空氣消耗流率、冷端流率與溫度、及能源效率；接著使用田口法分析各幾何參數對渦流管性能之貢獻度，考量參數包括冷端管徑、入口面積、及渦流管長與管徑，並依貢獻度系統化地分析其對性能之影響，進而完成性能最佳化之渦流管設計。為確認渦流管數值模擬之可信度，利用3D列印製作實體模型以供進行其性能量測，並將此實驗數據與模擬預估結果交互比對，以驗證此數值所得之渦流管最佳化結果。
數值與實驗之數據比對結果顯示，空氣消耗量差異約在5%內，而冷、熱端溫度差異值也都在3°C之內，可見本研究之數值模擬有一定的可信度。數值分析的結果顯示，最佳化模型於各操作壓力的空氣消耗流率皆遠低於原始模型，而冷端流率除不適用的低操作壓力外，皆能產生相同甚至更高之流量，這代表消耗較少能源便可獲得更高的冷卻性能。在操作壓力60 psig時，其冷端溫度由6.9°C降至5.5°C，且能源效率由0.0491提升至0.0697(41.9%)；而操作壓力80 psig時，冷端溫度由6.6°C降至6.4°C，能源效率由0.0485提升至0.0698(43.9%)，在兩個常使用操作點之各項性能皆大幅提升，清楚呈現出最佳化後的性能改善結果。最後藉由無因次分析推導渦流管性能對應的無因次函數式，接著將上述模擬所得資料，據以找出正確之無因次關係式；此關係式可用於設計出不同尺寸的渦流管，並可輕易計算出其預估的冷端流率與溫度，可供作為渦流管重要且方便的設計工具。

Vortex tube (VT) is a small mechanical device with no moving part for separating the high-pressure airflow into hot and cold streams without using refrigerant and power input. Due to the features of simple configuration, easy installation, and free maintenance, it becomes the perfect localized cooling choice for machining process, and the topic of this thesis. This integrated CFD, mockup fabrication, and experiment research aims to optimize the cooling performance of VT by analyzing key geometric parameters systematically. First, referred to previous researches, a VT model is constructed and used to execute numerical calculation for yielding its thermal/velocity distributions, flow patterns, and performance variables, mainly including the compressed air consumption, the temperature and flow rate at cold stream outlet, and the energy efficiency. In addition, Taguchi method is applied to evaluate the corresponding performance contribution of important parameters, which include the inlet area of nozzle, the cold-outlet diameter, the dimension of main tube. It is found that the dominant parameters are the cold-exit diameter and the VT length. Accordingly, a comprehensive parameter analysis is carried out within the framework of CFD codes Fluent to identify the corresponding performance influence of each variable, which can be used to attain the design guideline and the optimized model of vortex tube.
Afterward, mockup of the optimum VT is manufactured via the 3D printing technology for measuring its performance characteristics. As a result, an acceptable 5% air consumption and 3℃ temperature differences between test and CFD outcomes are recorded to validate the reliability of numerical model. Generally, CFD results show that the optimized model has a much lower air consumption than that of the original VT while the cold flow rate is maintained at the same or higher level for the practical operating pressures. It follows that a superior cooling performance can be achieved with a smaller energy consumption. Furthermore, significant performance improvements of this optimized VT are obtained at the frequently-used operating points. At operating pressure of 60 psig, the cold-end temperature drops from 6.9°C to 5.5°C while energy efficiency increases from 0.0491 to 0.0697 (i.e., 41.9% increase). For the higher operating pressure 80 psig, the cold-end temperature decreases from 6.6°C to 6.4°C while energy efficiency enlarges from 0.0485 to 0.0698 (i.e., 43.9% growth). Moreover, to generalize this optimal research, the dimensional analysis is applied on the vortex tube to generate the corresponding nondimensional performance parameters. And, with the aids of CFD results, their functional relations are determined with an accurate 5% deviation. In conclusions, the accomplishment of this work provides a systematic design scheme for constructing the optimized vortex tube to meet the specific requirements in the practical applications. Also, the nondimensional formular offers a ready-to-use design tool for creating different sizes vortex tube in a convenient manner.

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