Deep-borehole heat exchangers (DBHE) are generally coaxial pipes installed in deep boreholes and has become an alternative approach to utilize geothermal energy. Since the performance of the DBHE system can be affected by several parameters, it is important to optimize the design of parameters for the DBHE. In this paper, based on the analytical method, we carried out the sensitivity analysis of DBHE design parameters, including outer pipe diameter, inner pipe diameter, flow rate, outer pipe materials, grout materials, and borehole depth during continuous operation for 4 months. The sensitivity analysis results indicate that the heat extraction rate can be significantly affected by outer pipe diameter, borehole depth, and flow rate. The effects of grout materials, inner pipe diameter and outer pipe materials are of second-order. Finally, an optimization method based on the lowest Average Energy Cost index was proposed to optimize these DBHE design parameters under different geological conditions. Given the cost in this study, a combination scheme of all the optimal parameters is given for different depth wells under different geological conditions.

中文翻译：

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深孔换热器利用率的优化

深孔热交换器（DBHE）通常是安装在深孔中的同轴管，已成为利用地热能的另一种方法。由于DBHE系统的性能会受到多个参数的影响，因此优化DBHE的参数设计非常重要。本文基于分析方法，对连续运行4个月的DBHE设计参数进行了敏感性分析，包括外管直径，内管直径，流量，外管材料，灌浆材料和井眼深度。敏感性分析结果表明，热量吸收率会受到外径，管径和流速的显着影响。灌浆材料，内管直径和外管材料的影响是二阶的。最后，提出了一种基于最低平均能源成本指数的优化方法，以优化不同地质条件下的DBHE设计参数。考虑到本研究的成本，给出了在不同地质条件下针对不同深度井的所有最佳参数的组合方案。