The deep borehole heat exchanger (DBHE) coupled ground source heat pump (GSHP) system is widely developed in recent years to extract geothermal energy for building heating. However, its operating mechanism and energy flows within different components have not been comprehensively investigated. Meanwhile, the high outlet temperature of DBHE has the potential to meet the direct heating requirement but may exceed the GSHP’s temperature threshold. Therefore, this study first presented a hybrid DBHE heating system transient model with direct heating and coupled GSHP approaches using TRNSYS and MATLAB software. The novelty of this system is that DBHE was also coupled with a heat exchanger (HEX) to realize direct heating. Taking a residential building in Xi’an and DBHE with the depth of 2000 m as a scenario, the operation behavior and energy performance of the system were analyzed. The results showed that HEX will operate for several days before operating GSHP at the beginning of heating season, and annual HEX operating time gradually decreases from 27.1 days to 8.8 days over 10 years. Annual energy fraction of heat extracted from the soil by the HEX and GSHP in the total heating demand gradually decreases from 0.14 to 0.05 and increases from 0.72 to 0.78 over 10 years, respectively. Further, the importance of HEX in system performance was evaluated. Compared with the hybrid system, the GSHP’s COP will be overestimated by 11.3 % and the heat extraction amount will be significantly underestimated when HEX is not designed in the DBHE system. Moreover, the effects of different building heating load characteristics (including actual load and constant load) on system performance were discussed. It was found that the minimum inlet temperature of DBHE during the heating season under constant load will be overestimated, with a maximum deviation of 8.4 °C. Dynamic building load also results in a parabolic soil temperature isotherm at the end of heating season.

近年来，深孔热交换器（DBHE）耦合地源热泵（GSHP）系统被广泛开发，以提取地热能用于建筑供暖。然而，其运行机制和不同组件内的能量流尚未得到全面研究。同时，DBHE 较高的出口温度有可能满足直接加热要求，但可能超过地源热泵的温度阈值。因此，本研究首先使用 TRNSYS 和 MATLAB 软件提出了一种采用直接加热和耦合地源热泵方法的混合 DBHE 加热系统瞬态模型。该系统的新颖之处在于DBHE还与热交换器（HEX）耦合以实现直接加热。以西安某住宅楼和深度为2000 m的DBHE为场景，分析了系统的运行行为和能量性能。结果表明，在采暖季开始运行地源热泵之前，HEX 将运行几天，并且每年 HEX 运行时间从 27.1 天逐渐减少到 8.8 天超过 10 年。HEX 和 GSHP 从土壤中提取的热量在总供暖需求中的年能量分数在 10 年内分别从 0.14 下降到 0.05 并从 0.72 上升到 0.78。此外，还评估了 HEX 在系统性能中的重要性。与混合系统相比，在DBHE 系统中未设计HEX 时，地源热泵的COP 将被高估11.3%，而取热量将被显着低估。而且，讨论了不同建筑供暖负荷特性（包括实际负荷和恒定负荷）对系统性能的影响。研究发现，定负荷下采暖季DBHE的最低进风温度会被高估，最大偏差为8.4℃。动态建筑负荷也会导致供暖季节结束时的抛物线土壤温度等温线。