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頁籤選單縮合
題名 | 共軛梯度法於結霜厚度之預測 |
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作者 | 黃正弘; 林浩暉; | 書刊名 | 成大造船工程學報 |
卷期 | 26 民90.01 |
頁次 | 頁18-39 |
分類號 | 440.12 |
關鍵詞 | 共軛梯度法; 結霜厚度; 反算問題; Inverse problem; |
語文 | 中文(Chinese) |
中文摘要 | 當冷凍系統蒸發器盤管之表面在0℃以下,且低於入口處空氣之露點溫度時,則空氣中所含之水蒸汽就會分離附著於蒸發器表面形成霜。若霜的厚度很薄,對盤管的熱傳有所助益,但太厚,則有如在蒸發器表面加上一層絕熱材料般,對熱傳有很大的傷害,而且隨著霜厚度的增加,空氣流道會變窄,風量會變少,冷凍能力及吸氣壓力會下降,壓縮機效率也會惡化。嚴重時,風扇表面會結冰以致風扇卡死,造成送風馬達燒毀。由此可知,結霜對整個冷凍循環造成相當不良的影響。對於超低溫冷凍庫而言,此種情形更是敏感,因為無論單段或是二段式壓縮系統,其巨大的溫度降需要相當大的壓縮費用,結霜所造成的負面影響更形顯著。 本研究之目的即在利用“反算問題”(Inverse Problem)之技巧藉著溫度之量測來預測霜之厚度。“反算問題”目前來講是解決許多複雜工程問題最常見的方法之一,它的優點在於所預測之未知量並非僅解某些數學統御方程式,而是配合了一些“量測資料”來對問題做最佳化之計算。因此藉由反算問題之技巧,吾人不但可以預測得較真實的物理量,往往也同時可將問題更進一步的簡單化。 |
英文摘要 | Measurement of surface water waves with subsurface pressure transducer has been employed over the last five decades. However adequate pressure transfer function relating wave and pressure amplitudes is required to yield accurate results. Previous formulas of pressure transfer function are reviewed first in this paper and important characteristics of pressure transfer function are delineated. Among these characteristics, we show a strong dependency of pressure transfer function on the frequency parameter and also on pressure transducer submergence parameter, i.e., the pressure transfer function is a function of both relative depth and transducer submergence parameter. This is contrary to the conclusion of Kuo and Chiu (1994) where the empirical formula for the pressure transfer function is independent of transducer submergence parameter. Alternative noise correction method are also studied in this paper in order to avoid excess high-frequency wave spectrum components when converting from the pressure spectrum. Field pressure data are then used to calculate the wave spectrum using linear and nonlinear transfer functions, linear transfer function with correction factor, and empirical formula of Kuo and Chiu (1994). Considerable and unreasonable difference exists between empirical formula and the other three theoretical formulations. We therefore recommend that the empirical transfer function should be grouped in small range of transducer submergence parameter as suggested by Baqerizo and Losada (1995). |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。