Transient heat transfer model of a three-dimensional spiral heat source in an energy pile
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摘要: 將螺旋埋管等效為三維螺旋線熱源,考慮螺旋埋管能源樁的傳熱過程,運用格林函數和第一型曲線進行積分,推導給出了考慮時間、空間位置、埋管參數和巖土體熱物理性質4參數的螺旋埋管能源樁的溫度場解析解,建立高精度三維螺旋埋管能源樁的傳熱模型。并通過在數值模擬軟件中建立螺旋埋管能源樁三維模型,依據邊界條件,求解得出三維螺旋埋管能源樁溫度場數值解。對比結果表明:所建立的能源樁三維螺旋線熱源模型具有很高的解析精度。最后,基于解析模型討論了螺旋埋管能源樁換熱溫度場的空間分布和時間效應。Abstract: An energy pile is a new type of ground source heat pump system. A heat exchanger is casted into the concrete pile foundation of a building structure for the purpose of heating or cooling the building through heat exchange between the pile foundation and surrounding soil. An energy pile can be developed rapidly because of its high heat transfer efficiency and stable structure and because it requires no additional drilling requirements. In the long-term operation, energy piles have to bear both the overlying and thermal loads caused by changes in the temperature field. Thus, accurately evaluating the temperature field of an energy pile and its surrounding soil is one of the key problems in the design and application of energy piles. To improve the heat transfer efficiency of energy piles, U-type, W-type, spiral type, and similar types of coils have been developed to be casted into the energy pile. Results of thermal efficiency analysis show that the spiral type coil has the best heating and cooling performance and was nearly 150% more thermally efficient than the double U-type coil. Thus, a spiral coil is selected as the main coils’ form in the current practical application. However, due to the complex heat exchange structure of the spiral pipe, the present analytical model had to be simplified to accurately characterize the temperature field characteristics of a spiral pipe casted in an energy pile. In this paper, the spiral pipe was regarded as a three-dimensional spiral heat source. Considering the existing heat transfer model, an analytical solution of the temperature field was obtained by integrating green’s function and the first curve function; then, the high-precision, three-dimensional (3-D) heat transfer model of the spiral pipe was established considering the time, space, buried pipe parameters, and thermal property of host soil. In addition, a 3-D model of a spiral pipe casted in an energy pile was created in the numerical simulation software COMSOL; after simulation, the numerical solution of the temperature field was obtained. The contrastive results showed that the built 3-D spiral heat source model has high analytical accuracy. Finally, based on the analytical model, the spatial distribution and time effect of a spiral pipe casted in an energy pile were discussed.
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Key words:
- energy pile /
- spiral pipe /
- heat transfer model /
- temperature field /
- analytical solution
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表 1 數值模型參數
Table 1. Parameters of numerical simulation
Description Parameters Values Description Parameters Values Heat conductivity kiso/(W·m?1·K?1) 1.3 Burial depth Hspi/m 3 Thermal capacity Cp/(J·kg?1·K?1) 840 Helical pitch bspi/dm 3 Soil density rho/ (kg·m?3) 1460 Helical diameter rspi/dm 1 Calculated length Liso/m 4 Initial temperature Tcomp1/K 288.15 Calculated depth Hiso/m 4 Dirichlet temperature T0/ K 288.15 Calculated width Wiso/m 4 Heat consumption Ql/ W 20 Neumann boundary P0/ W 5 www.77susu.com -
參考文獻
[1] Cheng C J. Study on the Thermo-mechanical Properties of Concrete and Heat Transfer Behaviors of Energy Piles [Dissertation]. Wuhan: China University of Geosciences, 2016程超杰. 能源樁樁身材料熱−力學特性及換熱性能研究[學位論文]. 武漢: 中國地質大學, 2016 [2] Zhang P F. The general developing situation of ground-source heat pump at abroad and an initial inquisition into its application prospect to China. Refrigerat Air-condition, 2003, 3(3): 12 doi: 10.3969/j.issn.1009-8402.2003.03.004張佩芳. 地源熱泵在國外的發展概況及其在我國應用前景初探. 制冷與空調, 2003, 3(3):12 doi: 10.3969/j.issn.1009-8402.2003.03.004 [3] Brandl H. Thermo-active ground-source structures for heating and cooling. Procedia Eng, 2013, 57: 9 doi: 10.1016/j.proeng.2013.04.005 [4] Morino K, Oka T. Study on heat exchanged in soil by circulating water in a steel pile. Energy Build, 1994, 21(1): 65 doi: 10.1016/0378-7788(94)90017-5 [5] Pahud D, Fromentin A, Hubbuch M. Heat exchanger pile system for heating and cooling at Zurich airport. IEA Heat Pump Centre Newsletter, 1999, 17(1): 15 [6] Zhao Q, Chen B M, Liu F. Study on the thermal performance of several types of energy pile ground heat exchangers: U-shaped, W-shaped and spiral-shaped. Energy Build, 2016, 133: 335 doi: 10.1016/j.enbuild.2016.09.055 [7] Hamada Y, Saitoh H, Nakamura M, et al. Field performance of an energy pile system for space heating. Energ Buildings, 2007, 39(5): 517 doi: 10.1016/j.enbuild.2006.09.006 [8] Sekine K, Ooka R, Hwang S, et al. Development of a ground-source heat pump system with ground heat exchanger utilizing the cast-in-place concrete pile foundations of buildings. ASHRAE Trans, 2007, 113: 558 [9] Shiba Y, Ooka R, Sekine K. Development of high-performance water-to-water heat pump for ground-source application. ASHRAE Trans, 2007, 113(2): 122 [10] Omer A M. Ground-source heat pumps systems and applications. Renewable Sustainable Energy Rev, 2008, 12(2): 344 doi: 10.1016/j.rser.2006.10.003 [11] Farabi-Asl H, Chapman A, Itaoka K, et al. Ground source heat pump status and supportive energy policies in Japan. Energy Procedia, 2019, 158: 3614 doi: 10.1016/j.egypro.2019.01.902 [12] Liu H L, Kong G Q, Wu H W. Applications of energy piles and technical development of PCC energy piles. Chin J Geotech Eng, 2014, 36(1): 176 doi: 10.11779/CJGE201401018劉漢龍, 孔綱強, 吳宏偉. 能量樁工程應用研究進展及PCC能量樁技術開發. 巖土工程學報, 2014, 36(1):176 doi: 10.11779/CJGE201401018 [13] Zarrella A, Carli M D, Galgaro A. Thermal performance of two types of energy foundation pile: Helical pipe and triple U-tube. Appl Therm Eng, 2013, 61(2): 301 doi: 10.1016/j.applthermaleng.2013.08.011 [14] Zhao Q. Study on the Heat Transfer of Spiral-Tube Heat Exchangers in Energy Piles [Dissertation]. Jinan: Shandong University, 2018趙強. 螺旋埋管能量樁換熱器的傳熱研究[學位論文]. 濟南: 山東大學, 2018 [15] Eskilson P, Claesson J. Simulation model for thermally interacting heat extraction boreholes. Numer Heat Transfer, 1988, 13(2): 149 [16] Kavanaugh S P. Simulation and Experimental Verification of Vertical Ground-Coupled Heat Pump Systems [Dissertation]. Oklahoma: Oklahoma State University, 1985 [17] Diao N R, Fang Z H. Ground Source Heat Pump Technology. Beijing: Higher Education Press, 2006刁乃仁, 方肇洪. 地埋管地源熱泵技術. 北京: 高等教育出版社, 2006 [18] Zeng Y H, Fang Z H. A heat transfer model for double U-tube geothermal heat exchangers. J Shandong Inst Architect Eng, 2003, 18(1): 11曾義和, 方肇洪. 雙U型埋管地熱換熱器的傳熱模型. 山東建筑工程學院學報, 2003, 18(1):11 [19] Shi L, Zhang F F, Lin Y, et al. The 2-D thermal analysis of the coil ground heat exchanger inside piles. J Shandong Jianzhu Univ, 2010, 25(2): 177 doi: 10.3969/j.issn.1673-7644.2010.02.018石磊, 張方方, 林蕓, 等. 樁基螺旋埋管換熱器的二維溫度場分析. 山東建筑大學學報, 2010, 25(2):177 doi: 10.3969/j.issn.1673-7644.2010.02.018 [20] Wu D. Study on Heat Transfer Model for Pile Ground Heat Exchangers [Dissertation]. Jinan: Shandong Jianzhu University, 2009武丹. 樁埋管換熱器傳熱模型的研究[學位論文]. 濟南: 山東建筑大學, 2009 [21] Li X, Fang L, Zhao Q, et al. Coil heat source model and analytical solution of spirally buried tube heat exchanger. J Eng Therm Energy Power, 2011, 26(4): 475李新, 方亮, 趙強, 等. 螺旋埋管地熱換熱器的線圈熱源模型及其解析解. 熱能動力工程, 2011, 26(4):475 [22] Man Y, Yang H X, Diao N R, et al. Development of spiral heat source model for novel pile ground heat exchangers. HVAC&R Res, 2011, 17(6): 1075 [23] Yang S M, Tao W Q. Heat Transfer. 4th Ed. Beijing: Higher Education Press, 2006楊世銘, 陶文銓. 傳熱學. 4版. 北京: 高等教育出版社, 2006 [24] Hou Z B, He S J, Li S X. Solid Heat Conduction. Shanghai: Shanghai Science and Technology Press, 1984侯鎮冰, 何邵杰, 李恕先. 固體熱傳導. 上海: 上海科學技術出版社, 1984 [25] Zou G D, Shen Y F. A new method of temperature field calculation—the virtual heat source method. Mech Pract, 1993, 15(5): 49鄒廣德, 沈玉鳳. 溫度場計算的一種新方法——虛設熱源法. 力學與實踐, 1993, 15(5):49 -