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標題: | 垂直埋設式U型管淺層土壤溫能熱交換器之熱傳增強研究 Investigation of Thermal Performance Enhancement on Soil Heat Storage using Borehole Heat Exchangers |
作者: | Hsuan-Shih Kuo 郭軒志 |
指導教授: | 陳希立 |
關鍵字: | 土壤熱交換器,U型管,流場模擬,熱傳增強,最佳化,Fluent, Borehole Heat Exchangers,CFD,Fluent,Heat Coupling,Air-Conditioner,Soil,Geothermal Heat Pump, |
出版年 : | 2009 |
學位: | 碩士 |
摘要: | 使用垂直式U型管土壤熱交換器作為空調系統冷卻或取熱目的之技術在已開發國家盛行已久,如何在鑽井的設計上改良突破使得昂貴的初始架設能夠得到最大之效果,乃為一重要課題。本論文主要針對垂直式U型管土壤熱交換器系統的性能以及設計策略進行分析研究,首先建立由橫截面熱阻為主要構想之穩態數學理論模式之軟體進行分析,配合國外的實驗論文詳細資料進行正確性的驗證之後,以此為基準對影響最大的設計參數如最佳鑽井深度、回填土熱傳導性質、工作流體質量流率等進行最佳化分析。
同時,使用電腦軟體Fluent的模擬方式研究熱交換器以及土壤本身的熱擴散現象並與實驗數據進行正確性的驗證,確實正確無誤後便利用模擬方式研究各種熱傳增強策略對系統的影響;如入出口對調之交替式運轉,以及在固定鑽井尺寸之下改變管間距所帶來的系統暫態響應。 在本研究的案例模擬分析之下,在暫態的響應方面出口溫度在增加管間距最高可以有攝氏1度的溫降,在系統趨於穩態之後亦有超過攝氏0.5度的溫差。在其他的案例方面,雖然無法得到顯著的成效,但歸功於全三維的系統模擬分析,吾人可以對土壤熱交換器內的熱傳行為以及各散熱增強策略對系統內部細部影之影響有一全面的了解,作為往後研究改良的基礎。 The use of vertical U-shaped borehole heat exchangers for air-conditioning purposes has been widely practiced in the developed nations for a long time. The objective of maximizing system performance by an optimized design for borehole heat exchangers is of significant importance, for it’s hardly changeable after initial installation. Current thesis conducted thorough analysis and investigated several design strategies on borehole heat exchangers, First by setting up computer programs for steady mathematical analytic model for borehole heat exchangers for further analysis. After verifying the accuracy of the mathematical model by comparing with foreign experimental studies, the experimental settings is then to be used as a baseline for optimization on dominant design parameters such as optimal borehole depth, grout thermal conductivity and mass flow rate of working fluid. Also, the studies regarding the heat conducting behavior and characteristics inside and outside the borehole heat exchangers is conducted using Fluent, a commercial computational fluid dynamics software. After the simulation results are verified to be correct, further thermal enhancement strategies is then studied using simulation method to observe the effect on transient response of the system, such as oscillating operation, and inlet/outlet pipe spacing adjustment of single U-tube borehole heat exchangers. The results of simulation described in the thesis, the transient response of outlet temperature can be reduced by a maximum if 1degree Celsius, and after the system reaches equilibrium the outlet temperature is still reduced by 0.5degree Celsius. Although there is no significant improvement using other strategies, the full 3D flow & energy field analysis still enable us a whole view of the detailed thermal behavior inside the borehole for future reference of improvement. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/43765 |
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顯示於系所單位: | 機械工程學系 |
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