| 摘要 | 地埋管地源热泵系统（Ground-Coupled Heat Pump systems，GCHPs）是随全球能源环境问题的可持续发展而逐渐兴起的一门节能环保技术。国内外对地埋管地源热泵系统的研究集中在地埋管换热器与周围土壤间的耦合关系以及地埋管换热器的合理设计上。
有关地埋管换热器的传热计算，迄今为止还没有普遍公认的模型和规范。本文汇总分析了现有的地埋管换热器传热模型和垂直U形地埋管换热器传热模型。地埋管换热器传热模型有解析方法和数值方法两类，解析方法包括Ingersoll方法、Hart和Couvillison方法、IGSHPA方法以及Kavanaugh方法；数值方法包括Eskilson模型、Rottmayer Beekman和Mitchell模型以及Shoader和Beck模型。垂直U形地埋管换热器的传热模型有钻孔外部分和钻孔内部分，这些模型各具特色，本文分别对其进行了总结。鉴于线热源理论在长期运行、小管径的情况下具有较高的准确性，因此本文以线热源理论为基础建立地埋管换热器传热模型。
在对现有地埋管换热器传热模型进行总结分析的基础上，本文建立了垂直U形地埋管换热器的解析模型。首先针对单个钻孔进行研究，对钻孔外和钻孔内分别提出了一维（径向）线热源瞬态传热模型和稳态传热模型。考虑到埋管换热器和土壤之间的换热是随时间变化的，本文将一系列脉冲热流转化成一系列阶跃热流，使用叠加原理推导得钻孔壁温度计算式。在单个钻孔传热模型的基础上，采用叠加原理建立了多个钻孔的传热模型。使用该模型计算出循环流体的出口温度，与实测值相比，平均相对误差为2.56%，相对误差范围为-5.52 ~ 3.69%。
以上述U形地埋管换热器传热模型为基础，本文提出了基于逐时分析的地埋管换热器设计方法。该方法在已知建筑物设计负荷的情况下，以典型气象年室外逐时干球温度为基础计算建筑物逐时负荷。本文将水源热泵机组的性能参数拟合成二次曲线，并通过与实际水源热泵机组性能参数的比较说明了其适用性。之后从土壤的热物性、管材的选择、防冻液的选择、钻孔参数的确定以及地埋管换热器的长度计算等方面详细地分析了影响地埋管换热器设计的各个因素，进而提出了地埋管换热器的设计方法和步骤。
本文将该设计方法和步骤编制成计算机软件以方便地埋管换热器的设计。该软件很好地实现了本文提出的地埋管换热器设计方法，并具有自定义输入、智能读取、多种输出方式等优点。 |
| Abstract | Ground-Coupled Heat Pump systems (GCHP) , which has been identified as the most efficient and environment-friendly heating and cooling systems, is one of leading technologies of international HVAC industry. There are some key problems about GCHP popularized and applied. One of them is how to perfect heat-transfer model for ground heat exchanger (GHE) so actual thermal behavior of GHE can be credibly simulated, and other is designing method of GHE, which is most important to actual use in projects. This paper mainly analysis above two aspects.
Up to now, there haven’t a universal recognized model and standard for the model of GHE. This paper summarizes and analysis existing GHE models and existing U-tube GHE models. There are two kinds of model of GHE. One is analysis method, and the other is numerical method. The analysis method includes Ingersoll method, Hart & Couvillison method, IGSHPA method and Kavanaugh method. The numerical method includes Eskilson model, Rottmayer Beekman & Mitchell model and Shoader & Beck model. There are two kinds of U-tube GHE model too, they are outside of borehole and inside of borehole. Because of the veracity of line-source theory in small diameter tube and long period running, this paper uses line-source theory to build heat transfer model of GHE.
For a single borehole, a transient one-dimensional line-source model outside borehole and a steady-state model one-dimensional inside borehole are presented. These models consider the time-varying loads using superposition solution by heat pulse analysis and also consider intermittent operations of heat pump. Based on a single borehole, multiple boreholes heat-transfer model is achieved by a superposition technique. Compared calculated values used these models with experimental results, average error is 2.56%, and the error scope is -5.52 ~ 3.69 %.
Base on the U-tube GHE model above, a by-hour GHE designing method is presented. The mathod uses by-hour dry-bulb temperatures of Typical Meteorological Year to calculate building by-hour loads. To water-loop heat pumps, the method uses fitting curve method. This paper gave detailed designing method of U-tube GHE, including load calculation, pipe layout, choice of tubes and its material, antifreeze method, calculation of length of GHE, etc, and presents the step of designing of GHE.
In the last part of this paper, computer software is developed base on the designing method above. The software implements above designing method, and has merits of custom input, intelligence reading and multi-way output. |
