An energy pile is a special form of vertical ground heat exchanger that couples the roles of structural support and heat transfer. Modeling the transient heat transfer process inside an energy pile has importance; however, available analytical models either have insufficient calculation accuracy or are computationally demanding. Based on three existing models, this paper proposes a novel short-term hybrid composite-medium line-source (HCMLS) model, which is not only efficient in computation but also more accurate than most traditional analytical models. The model is suitable for ground heat exchangers of various radii. Comparisons between the hybrid analytical model and a numerical model are made for energy pile cases with different parameters, including the thermal properties, borehole radii, relative positions of tubes, and number of tubes. In general, the hybrid composite-medium line-source model gives credible prediction after 100 min. The new model is further validated by the infinite composite-medium line-source (ICMLS) model, which is currently the most theoretically complete short-term model. Moreover, the new model is applied to thermal response tests (TRTs). The least dimensionless test duration for interpretations based on the modified hybrid composite-medium line-source (C-HCMLS) solution is Fo > 1.7. This study renders the application of in situ TRTs to energy piles with large diameters feasible.

能量堆是立式地面换热器的一种特殊形式，它结合了结构支撑和传热的作用。对能量堆内部的瞬态传热过程进行建模非常重要。但是，可用的分析模型要么计算精度不足，要么对计算的要求很高。基于现有的三个模型，本文提出了一种新颖的短期混合混合中线源模型（HCMLS），该模型不仅计算效率高，而且比大多数传统分析模型更准确。该模型适用于各种半径的地面热交换器。针对具有不同参数（包括热特性，井眼半径，管的相对位置和管数）的不同能量桩情况，对混合分析模型和数值模型进行了比较。通常，混合复合介质线源模型在100分钟后给出可靠的预测。新模型通过无限复合介质线源（ICMLS）模型进一步验证，该模型是目前理论上最完整的短期模型。此外，新模型还应用于热响应测试（TRT）。基于改进的混合复合介质线源（C-HCMLS）解决方案的解释的最小无量纲测试持续时间为Fo  > 1.7。这项研究使原位TRT在大直径能量桩上的应用成为可能。