本研究與威技電器股份有限公司(NWT)合作進行，優化公司目前現有除濕機內部之扇葉幾何，以提升除濕機之出口風量表現，並期望未來能實際應用於公司之除濕機產品中，進而提高除濕機效率。台灣因地理位置與氣候條件長年處於高濕度的環境，在梅雨季節尤為明顯，使得除濕機已成為維持居家環境舒適與防霉抗濕的重要家電，提升效能則可有效改善能源使用效率與產品競爭力。為了達成以上目標，本研究首先針對現有除濕機機台進行實驗量測，獲得其扇葉轉速與出口風量，作為數值模擬之依據。接著在模擬方面，根據理論與實際運作情況建立統御方程式與邊界條件，建構一套含有熱交換器流阻條件之流場數值模型，利用計算流體力學方法模擬不同扇葉幾何對除濕機風量的影響。
在研究中先透過原型扇葉之實驗量測結果進行模擬驗證，並延伸採用前人所建立之NACA翼型扇葉與刀片型扇葉幾何進行模擬分析。結果顯示，在加入熱交換器後，各扇葉出口風量皆顯著下降，顯示熱交換器的流阻對整體性能影響甚鉅，且刀片型扇葉在出口風量表現上最為優異。然而，考量扇葉的製造限制，刀片型扇葉前緣之尖角結構不具製造可行性。故本研究以其為設計基礎，導入最小製造可行的圓角半徑0.3 mm，發展為導圓角刀片型扇葉。針對此幾何進行三項幾何參數(內徑r_i、葉片角度β、葉片數量N)之逐步組合優化，並優先將r_i值最佳的扇葉幾何進行模型製作與實驗驗證，其誤差結果小於2%。最後在參數組合為r_i=73 mm、β=-5°、N=45，得出風量最佳的導圓角刀片型扇葉，風量為0.0355 m3/s，此結果仍低於原型扇葉與刀片型扇葉。因此進一步針對葉片前緣圓角半徑進行探討，結果顯示，當圓角半徑由0.3 mm縮小至0.1 mm時，出口風量可提升為20%，顯示葉片前緣幾何為影響除濕機性能的關鍵設計因素之一。

Because of the high-humidity climate in Taiwan, particularly during its “plum rain season”, dehumidifiers are widely used in this country, and thus improving their performance is crucial for energy efficiency and product competitiveness. So, in collaboration with New Widetech Electric Co., Ltd. (NWT), this study aims to optimize the geometry of the fan blade in a dehumidifier to enhance its outlet airflow rate and overall efficiency. To that end, initial experiments were carried out on an existing dehumidifier to measure its airflow rate at various fan speeds, which are then used to validate the numerical results of the computational model developed in this work. Specifically, our computational model not only consists of the standard governing equations and boundary conditions of fluid dynamics, but also employs a simplified geometrical model to incorporate the flow resistance due to the heat exchanger (with more complex geometry) in the dehumidifier. Once validated, the computational model is used to examine how the fan blade geometry affects the airflow rate of the dehumidifier.

Technically, to aid in the optimization of blade geometry, first the prototype fan blade geometry is approximated by the NACA airfoil profile, and the resulting airflow rate at various fan speeds agree well with that of the actual prototype geometry and the experimental measurements. A systematic parameter study then is carried out. And the results indicate that the presence of the heat exchanger significantly reduced the airflow for all blade designs (as expected). Moreover, it transpires that the “knife-type” fan blade geometry would give the best performance. However, since its sharp leading edge posed significant manufacturability issues, we proceed to calculate and maximize the airflow rate of “rounded-tip knife-type” fan blades with a 0.3 mm fillet radius. And the results of our parameter study shows that when the blades have an inner radius r_i = 73 mm, a blade angle of β = -5°, and total blade number N = 45, the maximized airflow rate of 0.0355 m³/s can be achieved. But that unfortunately is lower than the original blade design. Nevertheless, further numerical results show that if the fillet radius at the blade tip can be reduced to 0.1 mm, an improvement (over the original blade geometry) in airflow rate of 20% still can be achieved. This finding emphasizes the importance of the leading-edge geometry of the blades in dehumidifier performance.

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