請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/48804
標題: | 利用淺層溫能之外氣處理熱交換器性能研究 The Performance Analysis of Earth-Air Heat Exchangers Using Shallow Geothermal Energy |
作者: | Chien-Yeh Hsu 徐千曄 |
指導教授: | 陳希立 |
關鍵字: | 地下空氣熱交換器,淺層溫能,外氣處理,通風空調,筏式基礎, earth-air heat exchanger,shallow geothermal energy,air pretreatment,ventilation,raft foundation,mat foundation, |
出版年 : | 2016 |
學位: | 博士 |
摘要: | 地下淺層溫能空氣熱交換器(earth air heat exchanger)是一種使用穩定的地下溫度做為熱傳主體的低耗能外氣通風技術。無論是透過理論或是現地實驗,在全世界有非常多針對地下空氣熱交換器的研究,但在台灣,以現地實驗為主軸的研究可說是近乎為零。因此本論文主要由現地實驗方式出發,分別針對土壤式空氣熱交換器與水式空氣熱交換器進行研究。針對土壤式空氣熱交換器所進行的實驗主要設施包括了七支50m長、直徑為0.25m並埋於3m深度的PVC空氣管道,以及可提供6800 m3/h送風量之離心式風機,通風時間則設定為在11:00至13:00間啟動系統進行通風。研究結果顯示,土壤式空氣熱交換器的全年加熱潛力高於冷卻潛力,而中午間歇式的操作方式則可有效利用較多的冷卻潛力。於2015年5月至2016年1月間的最大冷卻、除溼熱傳率為40kW,加熱熱傳率為15kW。透過本論文所開發、可計算時間效應與質量傳輸的計算模式,發現操作持續時間的選擇及空氣濕度比對熱傳量影響很大。本研究藉由回歸分析方式提出了針對操作時間及濕度比對交換係數(exchange coefficient)影響的計算公式,可用來進行熱傳量的估計。進一步為了提高地下空氣熱交換器的性能,本論文並針對了以水為主體的水式地下空氣熱交換器進行了實驗研究,主要對象包括了水平放置於充填水的建築地下筏式基礎裡的四支PVC空氣管道,管道平均長度為40m,管徑為0.2m,通風量為1460 m3/h。研究結果顯示,在1.3m深度的筏基水具有與2m以下土壤深度相近的冷卻潛力,而透過對建築周圍土地進行表面處理應可使水溫更加穩定,以期增加冷卻潛力。實際運轉測試表明,出口空氣溫度可有效趨近筏基水的溫度,在接近夏季氣候的測試亦可提供1.5 kg/hour至2.8 kg/hour之除溼量,而冷卻熱傳量為3.36 kW及3.66kW。本論文亦提出了針對水式地下空氣熱交換器的簡化模型,可做為尺寸分析使用。最後,針對兩種系統的回收年限分析顯示,經過適當的尺寸設計,兩系統的回收年限可分別為:土壤式為5年,水式為4年。 The earth air heat exchanger (EAHE) is a low-energy ventilation technique using the stable temperature of the earth. In the past decade, many experimental studies deal with the performance evaluation of EAHE system worldwide; however, in Taiwan these kinds of in-situ applications are still not available. This thesis presents a systemic approach to the analysis of two EAHE systems with different heat transfer media: water and soil. The soil-based systems were studied by means of long-term monitoring in Nantou, Taiwan, and analytical simulation. The experimental setup for the soil-based EAHE consists of seven parallel PVC pipes with 50m length and 0.25m diameter, buried at 3m depth beneath the ground surface, and a centrifugal fan with airflow rate of 6800m3/h. The operating strategy is to turn on the fan at 11:00 and turn off at 13:00. The results demonstrate that the annual acceptable cooling potential of soil-based earth-air heat exchanger may lower than the heating potential, but the midday intermittent operating can reach the maximum use of the cooling potential. The maximum total heat transfer rate ranged from -15 kW for heating, humidify, to about 40 kW for cooling, or dehumidify, during the period from May 2015 to January 2016. This thesis also develops an analytical model counting into the time delay effect and air humidity ratio. Through the analytical investigation, it was concluding that the effect of operating duration and latent heat exchange on performance is significant because they influence not only the temperature changes with time but also the exchange coefficient of soil. Intending to calculate the effect, dimensionless correlations were developed. Furthermore, to develop alternative efficient heat transfer media of earth air heat exchanger, an investigation for water-based system was also conducted in this thesis by an in-situ experiment in Yilan, Taiwan. The objective for the water-based EAHE consists of four air pipes with 40m length, 0.2m diameter, immersed in the water-filled raft foundation of a three stories building. A centrifugal fan with airflow rate of 1460 m3/h circulating the air into the system. The investigation shows that the cooling potential of the water beneath a building of 1.3m during spring season was close to that of ground soil at 2 m depth or deeper. The effect of changing the media around the air pipe of EAHE is significant. In addition, a suitable treatment of the ground surface is also important to avoid extra heat added into the water in the foundation. The in-situ experiment in three selected dates showed the air temperature could be dampened close to the average water temperature in the foundation. The ability of dehumidification was around 1.5 kg/hour and 2.8 kg/hour during hot season, and the averages of total heat transfer rate in hot weather was 3.36kW and 3.66kW, which was approximately equal to 1RT. In order to carry out the dimensioning of water-based EAHE, an analytical model was developed. Finally, the thermal and economic comparison between water and soil EAHE was presented, indicating that the water-based EAHE costs less than the soil-based one. The evaluated ROI periods are 4 years for water-based EAHE and 5 years for soil-based EAHE. The initial costs have huge effect on the ROI period, therefore an appropriate dimensioning was recommended in real application. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/48804 |
DOI: | 10.6342/NTU201603669 |
全文授權: | 有償授權 |
顯示於系所單位: | 機械工程學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-105-1.pdf 目前未授權公開取用 | 4.45 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。