水平式地埋熱交換器之性能計算分析研究

Numerical Analysis for the Performance of Horizontal Ground Heat Exchangers

吳顯佑(Hsien-Yu Wu)

指導教授 ： 陳發林

國立臺灣大學/工學院/應用力學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201800108

摘要

近幾年來，能源與氣候變遷等議題開始受到重視，各國家陸續發展綠能與實施節能減碳之措施，在能源使用之設備中，冷暖空調系統為占耗能的大宗，因此對於減少空調系統負載，在節能方面應有不錯的效果，地埋熱交換器與配合空調系統之使用是一種降低系統耗能的方式。
地埋熱交換器是由地層端地埋管與空調系統端所組成，是一獨立運作之系統，目的是為了與冷暖空調所排出之冷熱氣體熱交換，避免直接排放至空氣中浪費掉，藉由與地埋熱交換器管內之工作流體熱交換後帶入地底地層，地層全年之溫度變化幅度較地表上溫度變化小，在夏季時地層溫度低於地表空氣溫度，可將空調排出的熱存放在地層，當冬季時地層溫度高於地表空氣溫度，當空間需要暖房時，地層的熱藉由地埋熱交換器分擔空調的暖房負載，達到減少耗能之目的。
在本研究中，針對地埋管之熱傳性能進行分析，並改變其設計追求更好的熱交換性能，本研究設計了U型管及螺旋管並在外層加入不鏽鋼套管，及同心管式地埋管，模擬外加套管前後與不同流量條件及不同地層熱傳係數之結果，並針對各項結果進行優劣性比較及討論。
不同樣式之地埋管模擬結果，U型管與螺旋管在夏季與冬季模擬的熱交換熱能為螺旋管式較佳，在不同地層熱傳係數的條件，U型管與螺旋管結果隨著熱傳導傳係數增加而增加，增加的斜率為螺旋管較大；加了外套管前後之結果，性能的提升以U型套管增加幅度較大，不同地層熱傳係數的條件，在較低的地層熱傳外加套管之熱交換熱能較佳，但地層熱傳係數增加後，套管式的設計由於增加了回填材料，導致熱交換效果受到影響，模擬之結果為未加套管性能較佳；同心管式的設計因為可容許的工作流體流量較大，當流量增加時熱交換性能也隨之增加，在夏季時熱交換表現介於U型管與螺旋管之間，但在冬季的熱交換表現U型與螺旋式地埋管優於同心管。透過模擬結果可知依據裝置條件選擇合適的地埋管模型，對於系統運作的性能與效率才會有好的結果。

關鍵字

地埋熱交換器 ； 地源熱泵 ； 水平式地埋管 ； 地層熱能

並列摘要

In recent years, the issue of energy and climate change has received the attention. The policies of green energy and implementing energy saving with the carbon reduction in each country are gradually developed. In the energy use of equipment, heating and cooling air conditioning system are important. Therefore, to reduce air conditioning system load, we should have good results in energy saving, and the use of ground heat exchangers and air conditioning system is a way to reduce the energy consumption of the system.
Ground heat exchanger system composed of ground pipe and air conditioning system, and it is an independent system of operation. The purpose of Ground heat exchanger system is to exchange heat and cold gases from the air conditioning system, and avoid the direct air emissions. Heat energy is brought into the stratum by the heat exchange of fluids with the ground heat exchanger tubes, and the temperature change of the stratum is less than the surface temperature. In the summer, the stratum temperature is lower than the surface temperature. Stratum can store the thermal energy from the air conditioning system; in the winter, the stratum temperature is higher than the surface temperature. When the space needs heating, we can use stratum thermal energy of the ground heat exchanger to share air conditioning system load to achieve the purpose of reducing energy consumption.
In this study, the heat transfer performance of ground tubes was analyzed, and to change its design to have a better heat exchange performance. To design a U-type tube , spiral tube and the stainless steel casing is added to the outer layer, the results of simulation of stainless steel casing with different flow conditions and different ground thermal conductivity are compared and discussed in the results.
Different ground pipe simulation results of the U-type tube and spiral tube in summer and winter can show us that spiral tube is better than U-type. In different formation thermal conductivity conditions, U-type tube and spiral tube simulation results for thermal energy increase with the thermal conductivity. The increase of the slope of spiral tube results is larger than U-type; in addition to the results of stainless steel casing, the increase of U-type performance is larger than spiral tube. Different conditions of thermal conductivity can let us know that in the low thermal conductivity condition, the thermal energy of the casing is better, however, the thermal conductivity increases, casing design because of the addition of filler material. If reduce the heat exchange effect, the result of simulation is that no casing type performance is better; double pipe design allows a larger flow, when the flow rate increases, heat exchange performance also increases. In the summer, heat exchange performance is between the U-type tube and spiral tube, but in the winter, heat exchange performance of U-type and spiral pipe are better than double pipe. According to the simulation results, select the appropriate ground pipe model, we can have the best performance and have more efficiency of the system.

並列關鍵字

ground heat exchanger ； ground source heat pump ； horizontal buried tube ； ground thermal energy

參考文獻

[21]葉新晨, "多U型地埋管熱交換器之性能分析研究", 國立臺灣大學機械工程碩士論文, 2016.

[4]Florides, Georgios, and Soteris Kalogirou. "Ground heat exchangers—A review of systems, models and applications." Renewable energy 32.15 (2007): 2461-2478.

[5]Omer, Abdeen Mustafa. "Ground-source heat pumps systems and applications." Renewable and sustainable energy reviews 12.2 (2008): 344-371.

[7]Mihalakakou, G., Santamouris, M., Lewis, J. O., & Asimakopoulos, D. N. "On the application of the energy balance equation to predict ground temperature profiles." Solar Energy 60.3-4 (1997): 181-190.

[9]吳清吉, & 許武榮. "台灣土壤溫度分析和土壤熱擴散系數推估." 大氣科學 31.2 (2003): 115-130.