發(fā)布時間：2018-11-20 18:57

【摘要】：樁基埋管換熱器依托于建筑地下熱工結構,具有樁徑大、埋深較淺等特點,比傳統(tǒng)鉆孔埋管換熱器具有更為明顯的優(yōu)勢,如占地面積小、節(jié)省鉆孔費用及換熱器性能穩(wěn)定等,符合我國可持續(xù)發(fā)展戰(zhàn)略目標。其中,與樁基U型、W型等樁基埋管換熱器相比,樁基螺旋型埋管換熱器在同一樁基中不僅埋管長度較長、換熱面積更大,而且還可以防止氣體集聚在管道頂部。但是,樁基螺旋型埋管換熱器傳熱機理有異于傳統(tǒng)鉆孔埋管換熱器且?guī)缀谓Y構復雜,關于其傳熱性能的研究尚不夠充分。首先,本文利用ANSYS軟件建立樁基并聯雙螺旋型埋管換熱器三維動態(tài)傳熱的仿真模型,通過其對現場試驗的仿真復現以及與實心圓柱源熱源模型解析解的對比驗證了模擬結果的正確性。然后,由于不同埋管形式對換熱器與土壤換熱有重要影響,在管材、回填材料和土壤熱物性及邊界條件均相同的情況下,以實際尺寸的換熱器為原型,分別建立了樁基單螺旋型、并聯雙螺旋型與雙螺旋型埋管換熱器三維仿真模型,對以上模型在土壤中的非穩(wěn)態(tài)傳熱過程進行了模擬。結果表明:埋管形式不同,樁基埋管換熱器的換熱效果呈現差異,樁基雙螺旋型埋管換熱器的換熱性能最好,而單螺旋型優(yōu)于并聯雙螺旋型。然后,采用樁基單螺旋型埋管換熱器數值模型模擬了進口流速、進口水溫、土壤初始溫度、管徑及螺距對換熱器換熱性能的影響,得到各主要參數的傳熱變化規(guī)律。此外,結合建筑空調工程負荷特點,選定三種運停比,探討了各種間歇運行模式下樁基并聯雙螺旋型埋管換熱器的傳熱性能以及沿樁深和徑向不同位置樁基內部、樁壁及土壤溫度的變化規(guī)律,提出了以溫度恢復百分比為指標對樁基的溫度恢復特性進行定量評價的方法。最后,建立了樁基雙螺旋型樁基換熱器的熱濕耦合傳熱數值模型,利用該模型來研究地下水滲流作用下土壤溫度場分布情況及不同流速、土壤類型對周圍土壤的影響規(guī)律,并利用單位管長換熱量指標來評估滲流作用下樁基雙螺旋型換熱器的傳熱性能。本文的研究結果可為樁基螺旋型埋管換熱器實際工程設計及應用提供參考。
[Abstract]:The pile-base buried tube heat exchanger relies on the underground thermal structure of the building and has the characteristics of large pile diameter, shallow buried depth and so on. It has more obvious advantages than the traditional borehole buried tube heat exchanger, such as small area, low drilling cost and stable performance of the heat exchanger, etc. In line with the strategic objectives of sustainable development in China. Compared with the pile foundation U-type and W-type pile-embedded tube heat exchangers, the pile-foundation spiral buried tube heat exchangers not only have longer length and larger heat transfer area in the same pile foundation, but also prevent gas accumulation on the top of the pipe. However, the heat transfer mechanism of the pile-foundation helical buried tube heat exchanger is different from that of the traditional drilled buried tube heat exchanger and the geometry structure is complicated, so the research on its heat transfer performance is not enough. Firstly, the three-dimensional dynamic heat transfer simulation model of parallel double-helical buried tube heat exchanger with pile foundation is established by using ANSYS software. The correctness of the simulation results is verified by the simulation reappearance of the field test and the comparison with the analytical solution of the solid cylindrical heat source model. Then, because of the important influence of different buried tube forms on heat exchanger and soil heat transfer, the heat exchanger with actual size is used as prototype under the same conditions of pipe material, backfill material and soil thermal properties and boundary conditions. Three dimensional simulation models of single spiral parallel double helical and double helical buried tube heat exchangers are established respectively. The unsteady heat transfer process of the above models in soil is simulated. The results show that the heat transfer efficiency of pile based buried tube heat exchanger is different with different buried pipe types. The heat transfer performance of pile foundation double helical buried tube heat exchanger is the best, while that of single spiral heat exchanger is better than that of parallel double helical heat exchanger. Then, the effects of inlet velocity, inlet water temperature, soil initial temperature, pipe diameter and pitch on the heat transfer performance of the single spiral buried tube heat exchanger on pile foundation are simulated, and the heat transfer changes of the main parameters are obtained. In addition, combined with the load characteristics of building air conditioning engineering, three kinds of operation stop ratio are selected to discuss the heat transfer performance of parallel double-helical buried tube heat exchanger with pile foundation under various intermittent operation modes, as well as the different positions of pile foundation along pile depth and radial direction. Based on the variation of soil temperature and wall temperature, a quantitative evaluation method for the temperature recovery characteristics of pile foundation is put forward, which is based on the percentage of temperature recovery. Finally, a numerical model of heat and moisture coupling heat transfer in pile foundation double-helical pile heat exchanger is established. The model is used to study the distribution of soil temperature field and the influence of different velocity of flow and soil type on surrounding soil under the action of groundwater seepage. The heat transfer index of unit tube length is used to evaluate the heat transfer performance of double helical heat exchanger with pile foundation under percolation. The results of this paper can be used as a reference for the practical engineering design and application of spiral buried tube heat exchanger on pile foundation.
【學位授予單位】：西安建筑科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU83

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本文編號：2345703