Borehole heat exchangers, especially deep ones, are usually drilled through different geological layers having varying properties. Homogeneous and layered models can be used for borehole performance predictions. The homogeneous model considers all layers as a single layer having effective properties while the layered model considers all layers separately and gives better accuracy, although it is more complicated and time consuming to calculate. In this study, by considering real geological structures, thermal performance predictions of a deep borehole are made using both homogeneous and layered models and the results are compared to examine how predictions differ from each other depending on the statistical characteristics of geological structures. An analytical expression is derived for the relation between statistical characteristics and deviations from the predictions of the homogeneous model. The magnitudes of deviations are very small and essentially depend on the variance of the difference for the thermal properties of the layers and a time decaying function. The results help to understand how horizontally layered geological structures influence borehole performance and when we need a layered model.

钻孔换热器，特别是深部换热器，通常在具有不同特性的不同地质层中钻孔。均质和分层模型可用于井眼性能预测。均质模型将所有层视为具有有效属性的单层，而分层模型将所有层分开考虑并提供更好的精度，尽管计算起来更复杂且耗时。在这项研究中，通过考虑真实的地质结构，使用均质模型和分层模型对深孔的热力性能进行了预测，并对结果进行了比较，以根据地质结构的统计特征检验预测之间的差异。为统计特征与均质模型预测的偏差之间的关系推导了解析表达式。偏差的大小非常小，并且基本上取决于层的热特性和时间衰减函数的差异的方差。结果有助于了解水平分层的地质结构如何影响井眼性能以及何时需要分层模型。