臺灣博碩士論文加值系統

本研究為討論空調機於停機時所產生之水氣回吐造成室內人員不舒適之濕度條件的缺失，利用數值模擬改變排列方式、變蒸發器入口風速、鰭片間距、管間距以、管徑及管壁表面溫度的方式，試圖找出將冷凝水氣盡可能留在蒸發盤管上，進而減少壓縮機停機時回吐至室內之總量的最佳設計方式。
因此本研究先以實驗的方式分別利用A及B兩台冷氣機，量測於壓縮機運轉時與停機時出回風口的空氣狀態及盤管表面的溫度變化，並分析計算由空調機出風口回吐至空調區的冷凝水量。經計算後，發現較新的A冷氣機，由於盤管表面有親水性處理，所以回吐至室內的冷凝水氣幾乎只有微量，但仍可獲得進出口空氣狀態平衡時間約需30分鐘的重要結果。而B冷氣機為屬較舊的冷氣機，所以於壓縮機停機時段內，在送風量為193.810CFM，30分鐘的空氣狀態平衡時間下，可獲知停機時期初期最大回吐空氣之總熱回吐量約佔19﹪的空調負荷。
最後，本研究即針對B冷氣機於壓縮機停機時段作計算流體力學之數值模擬，由模擬結果可知，當交錯排列方式改為對齊排列方式時，可獲得0.3﹪的抑制率，而風速由傳統高速1.182m/s減小為0.4m/s時，出口空氣濕度比最大可增加1.1﹪，另外在相同入口風速下改變鰭片間距（FPI）由14FPI改為10FPI時，出口空氣濕度比最大可減少1.5﹪，而降低管壁溫度至-8℃可減少80﹪屬最具顯著抑制水氣回吐效果者。而改變管間距及管徑時，對出口空氣濕度比影響則不明顯。

This research is to investigate the defect of an air conditioner that evaporates and blows the moisture on the cooling coil back to the room space during compressor off cycle. This results are in thermal discomfort owning to the rising of humidity inside conditioned space. Experiments and numerical simulations were performed with changing various parameters such as coil layout, supply air velocity, fin pitch, evaporator coil spacing tube diameter and its surface temperature. In order to reduce the moisture blowing back to the minimal extend.
Two window-type air conditioners A and B were tested and the temperatures on cooling coil and air side, air flow rate as well as power consumptions under various conditions were obtained. The experimental results show that the amount of condensate on coil evaporating back to room space is very small using the newer air conditioner A for the hydrophilic coating of evaporator coil. It is also found that the refrigerant equilibrium time needed upon compressor sheeting down is about 30 minutes. On the other hand, the moisture blowing back to the space makes the cooling load rising about 19﹪ at supply air flow rate 193.8 CFM during the 30 minutes of equilibrium time when using the order air conditioner B.
A 3D simulation model was also established based on computational fluid dynamics to evaluate this phenomena. The numerical results using B as benchmark shows that, the restrain of total heat blowing back when off cycle under various conditions. When the coil layout was changed from staggered type to in-line type, the air velocity decreased from 1.182m/s to 0.4m/s, the fin pitch was changed from 14FPI (fin per inch) to 10FPI, tube surface temperature was changed are 0.3﹪, 1.1﹪, 1.5﹪and 80﹪ respectively. While the effects of changing evaporator tube spacing and diameter on reducing the total heat blowing back are very small.

摘 要..................................................iii
Abstract..................................................iv
目 次..................................................vi
圖目錄..................................................ix
表目錄..................................................xiii
符號說明..................................................xiv
第一章 緒論.........................................1
1.1 研究背景.........................................1
1.2 熱質傳現象與分析................................1
1.3 水氣回吐之意義.........................................6
1.4 研究動機及目的.........................................7
1.5 文獻探討.........................................8
第二章 研究方法與內容................................10
2.1 研究內容.........................................10
2.2 實驗方法.........................................10
2.3 數值模擬.........................................11
第三章 實驗設計與進行步驟................................12
3.1 實驗設計.........................................12
3.2 實驗設備與儀器.........................................14
3.3 實驗步驟.........................................16
3.4 實驗數據分析.........................................17
3.4.1濕度比之計算.........................................17
3.4.2 風量之計算.........................................18
3.4.3熱焓值之計算.........................................18
3.5 結果與討論.........................................18
第四章 理論模式與數值方法................................28
4.1 物理模型.........................................28
4.2 基本假設.........................................30
4.3 系統之統御方程式................................31
4.4 紊流模式.........................................32
4.5 牆函數概述.........................................33
4.6 統御方程式之數值方法................................33
4.6.1 軟體簡介.........................................34
4.6.2 結構性網格.........................................34
4.6.3 離散方法.........................................34
4.6.4 SIMPLE演算法則................................34
4.6.5 鬆弛因子.........................................37
4.6.6 收斂條件.........................................38
第五章 水氣回吐之影響分析................................39
5.1 影響蒸發器水氣回吐之重要因素.......................39
5.2 邊界條件.........................................40
5.2.1 空氣入口之溫度................................41
5.2.2 空氣入口之濕度比................................41
5.2.3 鰭片效率.........................................42
5.2.4 管壁與鰭片上之溫度與濕度比方程式..............43
5.3 格點獨立性.........................................44
5.3.1 空間格點獨立性................................46
5.3.2 時間格點獨立性................................51
5.4 監測面之設定.........................................52
5.5 數值模擬與實驗結果比較................................53
5.5.1 與傳統空調機正常控制模式之比較.......................53
5.6 空氣之氣流、溫度及濕度分佈情形.......................56
5.7 各因素對水氣回吐之影響................................62
5.7.1 排列方式之影響................................62
5.7.2 變風速之影響.........................................68
5.7.3 鰭片間距之影響................................73
5.7.4 管間距之影響.........................................78
5.7.5 管徑之影響.........................................83
5.7.6 管壁表面溫度之影響................................88
5.8 結果與討論.........................................93
第六章 結論與未來展望................................95
6.1 研究結論.........................................95
6.2 貢獻成果.........................................96
6.3 後續研究建議.........................................97
參考文獻..................................................98

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