臺灣博碩士論文加值系統

傳統空調系統大多採用冷卻水塔的散熱模式，不僅造成大量的能源耗費，其排放到外氣的廢熱也引發熱島效應。本論文旨在探討筏基水淺層溫能的應用，除了建立應用模式的理論模型，也與實際案例比較，探討其取代冷卻水塔的可能性。首先由熱傳分析來建立筏基水應用於空調散熱時的溫度變化模型，並與實測結果比對。經分析後的結果顯示，以總容量法預測的水溫與實驗數據幾乎吻合，誤差在3%以內，惟在筏基補水期間，因水溫的不均勻性提高而產生約10%的誤差。其次，考量溫度分層效應，以多個控制體積的能量分析來建立儲水槽的散熱模型。模擬結果顯示，當自來水補入流率為循環水流率的10倍時，儲水槽在接收約960 kW(≈273 RT)的空調負荷下能使水溫僅增加0.5℃左右。
本研究以熱阻分析得知筏基水自然散熱的速率受土壤側較大阻力影響，因此降溫速度不如前人預期，但若藉由補排水的流動機制仍能使筏基水溫低於主機的入水溫度限制。藉由CFD軟體的模擬驗證，以經驗公式計算的熱阻誤差約2%，在使用上是可接受的。另外，筏基水上方空氣層的熱傳率會因自然對流機制而提高，因此在設計上可進一步考量此現象是否會影響室內人員的舒適度。最後，在分析各案例的節能效益後可知，以筏基水溫能為空調系統的散熱模式節電率達21%，且每年可減少29,066公斤的碳排放量；而以儲水槽為空調系統的散熱模式節電率達24.6%，且每年可減少183,874公斤的碳排放量。

Most traditional air-conditioning systems use cooling towers to dissipate heat from cooling water to ambient air, which not only consumes lots of energy but also increases urban heat island effect. This thesis aims to investigate the application of raft foundation water shallow geothermal energy. By theoretically establishing a mathematical model and comparing it with experimental results, the possibility of replacing cooling towers with raft foundation system was evaluated. First, a model for predicting the temperature variation of raft foundation water was created and analyzed. The result showed good agreement between the predicted value and the experimental data, with an average error of 3%. However, during the time when fresh water was poured into raft foundation, due to the increasing non-uniformity of water temperature, the error went up to 10%, but still within acceptable range. Second, considering stratified phenomenon, a model based on analysis of multiple control volumes was created to predict the temperature variation within a huge water storage tank. The simulation results indicated the tank could receive cooling load of approximately 960 kW with little variation of water temperature when the flow rate of incoming tap water was 10 times as large as that of the circulation water.
Through heat transfer analysis, this research showed the heat dissipation rate from raft foundation water to surrounding soil was affected by the relatively high thermal resistance in soil, hence the cooling rate was not that fast compared with the former research. In addition, the thermal resistance calculated by empirical correlations was validated through CFD simulation, with only 2% relative error. Also, it was found that the heat transfer rate through the air enclosure on top of the raft foundation water was increased due to natural convection mechanism. As a result, more attention should be paid to determine whether or not this amount of heat dissipation would have significant impact on the residential quality. Finally, through energy saving assessment, it was shown that the usage of raft foundation water thermal energy could save up to 21% electricity and reduce carbon dioxide emissions by 29,066 kg per year ; and the usage of water storage tank system could save up to 24.6% electricity and reduce carbon dioxide emissions by 183,874 kg per year.

目錄
致謝 I
摘要 II
Abstract III
目錄 V
圖目錄 VIII
表目錄 XII
符號說明 XIV
第一章 緒論 1
1.1 前言 1
1.2 文獻回顧 4
1.2.1 土壤溫能 4
1.2.2 水溫能 7
1.2.3 筏基水溫能 7
1.3 研究動機與目的 8
第二章 基礎理論 10
2.1 筏基水溫變化之理論模型 10
2.2 熱阻分析 15
2.2.1 熱阻簡介 15
2.2.2 筏基水溫模型的熱阻計算 17
2.3 計算流體力學軟體Fluent簡介 22
2.3.1 統御方程式 22
2.3.2 紊流方程式 23
2.4 Fluent計算程序 25
2.5 Fluent數值方法 26
2.5.1 主要架構 26
2.5.2 網格系統 27
2.5.3 離散方程式 28
2.5.4 離散差分演算法 29
2.5.5 S.I.M.P.L.E. 演算法則 31
2.5.6 收斂標準 32
第三章 研究方法 33
3.1 筏基水溫實測 33
3.1.1 實驗設備 34
3.1.2 實驗步驟 36
3.2 筏基水溫模擬 37
3.3 理論模型之誤差分析 41
3.3.1 幾何建立 42
3.3.2 網格設定 44
3.3.3 Fluent求解器 48
3.4 儲水槽水溫模擬 52
3.5 節能效益分析 58
第四章 結果與討論 59
4.1 筏基水溫實測 59
4.2 筏基水溫模擬 61
4.3 理論模型之誤差分析 64
4.3.1 補水流率 65
4.3.2 筏基水溫的均勻性 67
4.3.3 筏基水上方的空氣層熱傳 69
4.3.4 筏基水側至土壤側熱阻 74
4.4 儲水槽水溫模擬 78
4.4.1 不同負載率 80
4.4.2 不同空調負載 83
4.5 節能效益分析 94
4.5.1 筏基水溫能散熱應用 94
4.5.2 儲水槽散熱應用 97
第五章 結論與建議 100
5.1 結論 100
5.2 建議 101
參考文獻 102

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