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首页> 外文期刊>International Journal of Heat and Mass Transfer >A new analytical heat transfer model for deep borehole heat exchangers with coaxial tubes
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A new analytical heat transfer model for deep borehole heat exchangers with coaxial tubes

机译：具有同轴管的深孔换热器的新型分析传热模型

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摘要

Deep borehole heat exchangers (DBHE) provide an effective solution for ground coupled heat pump (GCHP) systems in cold climate region where heating is dominant. Concerning the analytical heat transfer models, the simplification that borehole wall temperature is constant along the depth of ground heat exchangers (GHE) which the existing quasi-three-dimensional models have assumed in the application of shallow borehole GHE, can no longer be accepted in the application of DBHE due to the geothermal gradient in deep ground. Making this simplification cannot give the real temperature distribution of circulating fluid along the depth of DBHE. Therefore, this paper developed a new analytical model for DBHE with coaxial pipes by successfully addressing the increasing borehole wall temperature using the convolution theorem, so that the widely employed quasi-three-dimensional models for shallow borehole GHE is extended for DBHE with coaxial pipes for the first time. The new analytical model is validated by comparing with an existing numerical model. Using the newly developed analytical model, the trends revealing the relationships between thermal performance of DBHE and various parameters are firstly plotted. Because of the high accuracy and quick calculation, this new analytical model can be used as a benchmark for numerical models. More importantly, the proposed analytical model can be an effective tool for the design and optimization of DBHE, since current numerical models are always calculation-demanding, time-consuming and difficult for engineers and designers to use. Also, the method this paper proposed to address the varying borehole wall temperature can certainly be employed to improve the existing quasi-three-dimensional models for shallow borehole GHE so that they can be applicable in some other cases, for example, GHE installed in layered soils, or affected by underground seepage flow in partial depth. (C) 2019 Elsevier Ltd. All rights reserved.
机译：深孔换热器（DBHE）为以热量为主导的寒冷气候地区的地面耦合热泵（GCHP）系统提供了有效的解决方案。关于解析传热模型，现有的准三维模型在浅井GHE的应用中假设的井壁温度沿地面换热器（GHE）的深度恒定的简化不再被接受。 DBHE在深层地热梯度中的应用。进行这种简化不能给出沿DBHE深度的循环流体的实际温度分布。因此，本文通过使用卷积定理成功解决了井壁温度升高的问题，为同轴管道的DBHE开发了一种新的分析模型，从而为浅孔GHE广泛采用的准三维模型扩展了同轴管道DBHE的解析度。第一次。通过与现有数值模型进行比较来验证新的分析模型。使用新开发的分析模型，首先绘制了揭示DBHE热性能与各种参数之间关系的趋势。由于高精度和快速计算，这种新的分析模型可以用作数值模型的基准。更重要的是，建议的分析模型可以成为DBHE设计和优化的有效工具，因为当前的数值模型始终需要计算，费时且工程师和设计人员难以使用。同样，本文提出的解决变化的井壁温度的方法当然可以用来改进现有的浅孔GHE准三维模型，以便将其应用于某些其他情况，例如分层安装GHE土壤，或受部分深度的地下渗流影响。 （C）2019 Elsevier Ltd.保留所有权利。

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