竖直埋管换热器热响应半径计算方法
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浙江省自然基金项目(LY12D02001),浙江农林大学人才项目(2010FR099)


Calculation method of thermal response radius for vertical borehole heat exchangers
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    摘要:

    随着能源压力的日益增大,世界各国都十分重视可再生能源的利用与开发,地源热泵技术作为一种清洁、高效的可再生能源,近年得到了较快的发展。该文利用无限长线热源传热计算模型,讨论了介质内过余温度场的分布特性。结果表明:介质内温度响应在孔壁处最大,随离孔壁距离的增加呈指数衰减,随时间的增加而增大;热传播区域随时间的增加而增大,随介质的热扩散系数的增加而增大。针对工程中群埋管换热器情况,利用叠加原理计算群埋管的孔壁温度,定义换热器的热响应半径为其他钻孔引起的过余温度影响系数≤5%时相邻钻孔中心线之间的垂直距离。在大量计算分析基础上,提出了竖直埋管换热器热响应半径计算方法。计算结果表明该文方法具有较好的计算精度,竖直埋管换热器的热响应半径随岩土热扩散系数增大而增大,随持续运行时间增加而增大,随钻孔排数增加而增大,随着钻孔孔径增大而增大;钻孔布置方式不同对钻孔热响应半径的影响较明显,相同布置方式下钻孔直径对其热响应半径的影响较小。针对工程中常见的115和135 mm 2种孔径,绘制了不同岩土介质下钻孔单排、双排和三排以上布置时热响应半径-运行时间的关系曲线。工程算例表明该文方法简单方便,为工程设计提供了便利。

    Abstract:

    Abstract: At present, energy and environmental issues have become one of the most principal factors affecting the development of modern society. Energy conservation, exploitation of green renewable energy and environment protection has become urgent tasks in China. With the utilization of renewable energy sources and protection of environment, more and more researchers in the world pay attentions to the thermal environment of the geotechnical engineering. Some environment protection and energy saving technologies can cause the changes of soil temperature or even chemical contaminants diffusion, such as the development and utilization of shallow geothermal energy, nuclear waste disposal, landfill construction, thermal storage. Changes in the mechanical properties of the soil that caused by soil temperature field may lead to soil deformation, falling of ground stability and bearing capacity. Therefore, the research on heat transfer characteristics of rock and soil media has important theoretical values and practical significance in the development of geothermal resources, nuclear waste disposal, energy storage, landfill, heating pipe design and other aspects. The ground-source heat pump (GCHP) technology, as a clean and efficient renewable energy, has developed rapidly in recent decade. The distribution characteristics of the excess temperature in the soil medium were studied with the infinite line source heat transfer model in this paper. The results showed that the temperatures response at the surface of the borehole wall was the biggest in the soil medium around the ground, and heat exchanger which decayed exponentially with distance from the wall of the borehole, increased with operating time of the system. The heat transfer area also increased along with the thermal diffusion of medium and running time of the system. For the group of ground heat exchangers in the engineering, the temperature on the borehole wall of the group buried pipe was calculated according to the superposition principle, it was defined that the thermal response radius of the ground heat exchangers was the vertical distance between the adjacent borehole center when the excess temperature impact factor caused by other boreholes was less than or equal to 5%. With numerical analysis, the calculation method of the thermal response radius of the vertical ground heat exchangers was proposed. The calculating results showed that this method had better precision. The thermal response radius of the vertical ground heat exchanger increased along with the growth of the thermal diffusivity of the ground, duration of working time, borehole row numbers and borehole diameter, and was influenced significantly by the layout of the ground heat exchangers, and less by the borehole diameter under the same layout of the ground heat exchangers. In the case of common borehole diameter in the engineering, such as 115 and 135 mm, the graph of thermal response radius along with running time could be presented with different soil media of a single row, double rows and more than three rows drilling layout in this paper. The engineering examples showed that the method was simple and convenient for engineering design.

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李晓星,胡夏闽,张正威.竖直埋管换热器热响应半径计算方法[J].农业工程学报,2015,31(17):248-253. DOI:10.11975/j. issn.1002-6819.2015.17.033

Li Xiaoxing, Hu Xiamin, Zhang Zhengwei. Calculation method of thermal response radius for vertical borehole heat exchangers[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE),2015,31(17):248-253. DOI:10.11975/j. issn.1002-6819.2015.17.033

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  • 收稿日期:2015-01-30
  • 最后修改日期:2015-07-24
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  • 在线发布日期: 2015-09-01
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