帮我润色下：GEDWs墙体的换热量是评价热泵系统中GHEs换热效果优劣的最直观指标在很大程度上决定着热泵机组的运行性能。在工程实践中墙体的单位面积平均换热量Q是设计师需要参考的重要数据精确的Q值有助于合理的设置GHEs的管道布局为热用户的基本冷、热量消耗提供保障。 图4a b c分别给出了时间温度边界TDTB与恒定温度边界FTB条件下不同墙体埋深10m 20m 35m的单位面积平均换热量与出口温度

The heat exchange capacity of GEDWs wall is the most intuitive indicator for evaluating the heat exchange performance of GHEs in a heat pump system, and largely determines the operational performance of the heat pump unit. In engineering practice, the unit area average heat exchange capacity (Q) of the wall is an important data that designers need to refer to. Accurate Q values help to set up GHEs' pipe layout reasonably, providing assurance for the basic cooling and heating energy consumption of the heat users. Figures 4a, 4b, and 4c respectively show the variations of the unit area average heat exchange capacity and exit temperature of different wall depths (10m, 20m, 35m) under the conditions of Time Temperature Boundary (TDTB) and Constant Temperature Boundary (FTB). It can be observed that: (1) Under different wall depths, the unit area average heat exchange capacity of both FTB and TDTB decreases with time, initially rapidly and then gradually stabilizes. This is a natural rule during the operation process of GHEs [4,13,20]. Regardless of whether the heat pump unit is storing heat in summer or extracting heat in winter, the temperature difference between GHEs and the surrounding environment gradually decreases, leading to a reduction in heat exchange capacity. (2) The unit area average heat exchange capacity under FTB is higher than that under TDTB, and the difference between the two increases with time, but this difference decreases with the increase of wall depth. Taking the end of the second heating season as an example, the difference between the two decreases from 27.87% (10m) to 7.38% (35m). This is because during the cooling season, the shallow ground temperature under TDTB is higher than the average ground temperature under FTB (14℃), while during the heating season, it is lower than the average ground temperature under FTB. This results in a smaller temperature difference between GHEs under TDTB and the surrounding environment, leading to less heat exchange, and increasing influence with time. However, the deep ground temperature is consistent with the average ground temperature (FTB), and the proportion of shallow ground decreases gradually with the increase of wall depth, leading to a gradual reduction in the disturbance to the heat exchange capacity. (3) The unit area average heat exchange capacity during the cooling season is higher than that during the heating season. This is because the temperature difference between the fluid in the heat exchange pipe and the surrounding environment is greater during the cooling season than during the heating season. (4) During the operation of the heat pump unit, the exit temperature of GHEs under FTB and TDTB is almost the same, with only significant differences occurring during the intermittent period of the heat pump operation. Therefore, it can be seen that compared with FTB, the seasonal variation of ground temperature (TDTB) has a significant impact on the heat exchange capacity of shallow GEDWs wall (<20m), leading to a significant decrease in heat exchange capacity. The maximum percentage difference between the two during the cooling and heating seasons can reach 17.00% and 27.87%, respectively. Therefore, when conducting engineering design and simulation calculations, the impact of seasonal variation on the heat exchange potential of shallow GEDWs needs to be considered. In addition, although the seasonal variation (TDTB) reduces the heat exchange capacity of GEDWs, the exit temperature of GHEs under FTB and TDTB is almost the same during the heat pump operation, indicating that the heat pump unit can still meet the users' needs under TDTB conditions and does not have a significant impact on the user experience.