多U型地埋管熱交換器溫度解析模型建立與性能分析

Abstract

地埋管熱交換器應用於地源熱泵系統是一種常見的淺層溫能運用方式，其具有較好的永續性以及穩定性。針對各種不同型式的地埋熱交換器，如單U形、雙U形、能量樁等已有人進行過解析模型的建立與推導。本研究室設計出一與殼管式熱交換器運作模式相近的垂直式多U型地埋管熱交換器，透過殼側抽水進行強制對流來提升熱交換效果。本研究欲建立一溫度解析模型，並配合實驗對此熱交換器進行性能分析。 本研究建立之溫度解析模型對應到一垂直式多U型地埋管金屬熱交換器能有效的計算出穩態時，殼側的流體溫度分層，以及地埋管周遭的淺層土壤溫度分布情形，同時可以求得殼側抽水和土壤的散熱量，其與實驗值的誤差小於2%。另外對於另一垂直式多U型地埋管PVC熱交換器，本研究透過熱阻分析，找出一修正參數α_f，對使用Kern method計算得出的殼側對流熱傳係數修正，使其與實驗值相符，且誤差小於6%。

The use of ground-coupled heat exchangers in ground source heat pump systems is a common way of shallow geothermal energy application, which has good sustainability and stability. For various types of buried heat exchangers, such as single U-shaped, double U-shaped, energy piles, analytical models have been established and derived. A vertical multi-U type borehole heat exchanger, which has similar operation mode to the shell-and-tube heat exchanger was designed. Forced convection through shell side pumping enhances heat exchange. This study wants to establish a temperature analysis model and perform experiments on this heat exchanger for performance analysis. The temperature analysis model established in this study corresponds to a vertical multi-U type borehole metal heat exchanger that can effectively calculate the steady state temperature stratification of the shell side and the shallow soil temperature distribution around the buried pipe. Simultaneously, the amount of heat transfer rate of the shell side and the soil side can be obtained. The error against the experimental value is less than 2%. In addition, for another vertical multi-U type borehole PVC heat exchanger, in this study, through thermal resistance analysis, a correction parameter α_f was found. The shell-side convective heat transfer coefficient calculated by using the Kern method was corrected to match the experimental values, and the error is less than 6%.