Study on Performance Analysis of Multi-U type Borehole Heat Exchangers

• Main Authors: Hsin-Chen Yeh, 葉新晨
• Other Authors: Sih-Li Chen
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/90930814651237867846

碩士 === 國立臺灣大學 === 機械工程學研究所 === 105 === In recent years, greenhouse gas emissions and energy shortage crisis have caused renewable energy in much attention and one of among shallow geothermal energy is regarded as an effective method that can reduce greenhouse gases and therefore saving and cleaning green energy can be reached. Shallow geothermal energy is situated at the surface of the earth in 10 to 300 m range of low temperature energy. It cannot be influenced by the outside temperature and is considered as quite steady heat source or heat sink. In abroad, people have been used to grab heat from the surface of the earth by borehole heat exchanger for many years, the technology of which, therefore, is highly skilled. In addition, Taiwan has the advantage of developing shallow geothermal energy because of the soil rich in moisture, but currently there is only few application of shallow geothermal energy in Taiwan, so this research was focus on borehole heat exchanger in shallow geothermal energy. The study used Multi-U type Borehole Heat Exchangers (MUBHEs) that is made of PVC material tubes and the structure is almost similar to shell-tube heat exchangers. So, the study referred to Kern method of transitional heat exchanger theory model in which ho empirical equation is based on Res , and the correlation between ho and Res through experimental regression, ho = 30.127Res0.2196. Additionally, in an experiment, when the flow of Pump was 32.8 LPM, 13.2% heat dissipation was taken away from systems . If 32.8 LPM of flow of pump compared to no pumping, then saving initial drilling depth of system by 14.9 % was estimated. If using MUBHEs instead of cooling tower with 45 kW of cooling capacity in the same conditions, then at least 3 groups of MUBHEs were needed to cool the load.