Numerical Analysis for the Performance of Horizontal Ground Heat Exchangers

• Main Authors: Hsien-Yu Wu, 吳顯佑
• Other Authors: 陳發林
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/2w7anm

碩士 === 國立臺灣大學 === 應用力學研究所 === 106 === 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.