1、分类号： 密 级： UDC： 中 国 地 质 大 学博 士 学 位 论 文地埋管地源热泵水热耦合模拟与浅层地温能适宜性评价学 号：博 士 生：学科专业：水文与水资源工程指导教师：教授所在学院：环境学院年 月学校代码： 研究生学号： 中 国 地 质 大 学博 士 学 位 论 文地埋管地源热泵水热耦合模拟与浅层地温能适宜性评价博 士 生：学科专业：水文与水资源工程指导教师：教授年 月地埋管地源热泵水热耦合模拟与浅层地温能适宜性评价摘 要浅层地温能作为一种清洁能源，因为它的高效、无污染性，越来越多地被应用于城市居民的供暖与制冷当中。浅层地温能资源赋存于地表以下 200m 深的范围以内，具有分布广、储
2、量大的特点，现今的开发利用状况与它庞大的资源储量相比还有很大的开发空间。现今制约地埋管地源热泵技术发展的因素有很多，其中最主要的原因是由于对地埋管换热器与岩土体间的热量传递认识不全面，导致在前期盲目地设计，以至于换热器换热性能发生大幅下滑，给地埋管地源热泵的技术推广带来很大阻碍。因此，本文主要针对有、无渗流条件下地埋管地源热泵换热特性展开分析，就地埋管换热器与周围岩土体之间的换热过程进行更深层次的探究，并从区域尺度和场地尺度对浅层地温能的开发利用进行适宜性评价。 通过前期理论分析和福州地区实地的原位试验，利用数值模拟软件建立了无渗流和存在地下水渗流两种机制下地埋管换热器换热过程的数值模型。通过
3、引入换热器换热能效系数、有效换热持续时间及单位深度换热量三个参数，对地埋管换热器的换热特性及换热能力进行量化分析。分析了有渗流和无渗流作用岩土体中换热器换热性能的差异，并讨论了不同地埋管结构、岩土体性质以及冬夏不同热负荷特性条件下群管换热器换热性能的变化。针对多层型岩土体展开讨论，研究其单层岩土体中存在渗流流动时换热器换热特性的差异，并就热弥散作用对换热的影响展开初步探究。利用层次分析法对浅层地温能进行进行区域尺度的评价；采用数值模拟的方法针对实际工况对浅层地温能进行场地尺度的评价，主要得到以下结论：1.在无渗流条件下，热量以圆形辐射状向外部进行传输，容易产生热量的堆积，换热器在运行 10 年
4、后仍未达到局部热平衡；在有渗流流动（110 -6m/s）的条件下，热量在地下水上游的传输受到抑制，在水流下游的传输得到促进。渗流作用能有效减弱热量堆积的不利影响，且换热器在运行的第 100 天就能达到局部换热平衡状态。同时，渗流流动能提高地埋管换热器的换热能力，在连续运行的第 10 年，同比无渗流工况，换热器单位深度换热量增加了约 68%（060m 均存在渗流流动） 。2.在有无渗流两种条件下，岩土体初始温度的改变都不影响换热器换热能效系数的变化特征；但对于制冷工况，初始温度越低，地埋管换热器进出口温差会越高，有效换热持续时间也会越长。因此，对于有制冷需求大于制热需求的区域，岩土体温度越低越有
5、利于地埋管换热器长期高效地运行。3.地埋管换热器长度的增加能提高换热器换热能效特性及有效换热持续时间，但不意味着地埋管换热能力的增大。单位深度换热量是由总换热量及换热器深度 H 所共同决定的。在实际设计中要综合考虑换热器的数量及其深度大小。4.埋管管内循环流体须保持为紊流流态，在保证循环泵正常运行的前提下，流速越大换热器换热能力越大，但流量增大到 45m3/d（支管内径 0.031m）时，单位深度换热量相比流量为 35m3/d 的工况增加不足 5%，且流速过大对循环泵的要求也就越高。因此，应保证换热能力的同时兼顾运行费用的经济性，循环流体流量控制在 3545m3/d 之间。5.通过无渗流条件下
6、群管换热器运行的可持续性研究，可知浅层地温能也是有一定使用限度的，我们应该把浅层地温能看作“蓄能体”进行开发利用。6.相同运行工况条件下，渗流型群管换热器的运行可持续性明显优于无渗流条件下群管换热器的运行可持续性。7.埋设于多层型岩土体中的地埋管换热器，一般只在岩土体某一区段存在较明显的地下水渗流流动，渗流流速越大越有利于换热的进行。连续运行 100 天，可采用修正的Peclet 数对渗流换热的相对强弱进行判别：当修正 Pe 数=0.0041 时，换热器换热量同比无渗流时增大约 5%；当修正 Pe 数=0.1291 时，换热器换热量同比无渗流时增大约 30%。8.通过强制渗流的热渗耦合热响应试
7、验，对地埋管换热器进出口温度及处于渗流区段岩土体温度监测点的模拟值与实测值进行了比较，发现模拟值与实测值之间的误差在工程应用允许的范围内。说明本文所建立的渗流流动作用下的地埋管换热器换热模型是合理的，是可应用于工程设计当中的。9.根据区域性浅层地温能评价的结果，福州地区适宜和较适宜浅层地温能开发利用的地区主要集中于第四系海积平原和盆地周围第四系残坡积较为发育的地区，上述地区有易于钻进、含水层富水性好、径流交替强烈等特点。10.福州地区在场地尺度下要使得换热系统较为持续的运行，较为适宜的冷热负荷不平衡率应该不大于 45%。关键词：地埋管换热器 FEFLOW 水热渗耦合热响应试验 适宜性评价 He
8、at transfer modelling of the Borehole Exchanger under the groundwater flow and shallow geothermal energy suitability evaluationABSTRACTGeothermal heat is a viable source of energy and its environmental impact in terms of CO2 emissions is significantly lower than conventional fossil fuels. Shallow ge
9、othermal systems are increasingly utilized for heating and cooling buildings and greenhouses. However, their utilizations inconsistent with the enormous amount of energy available underneath the surface of the earth. Projects of this nature are not getting the public support they deserve because of
10、the uncertainties associated with them, and this can primarily be attributed to the lack of a comprehensive acquaintance with the heat transfer process between the Borehole Exchanger (BHE) and the surrounding soil. This shortage cause an arbitrary design for the BHEs, which would lead to the serious
11、 drop in performance of BHE. The uncertainties of the performance of the BHE would bring great barriers of the promotion of the new technology. For this energy field to have a better competitive position in the renewable energy market, it is vital that engineers acquire a proper understanding about
12、the Ground Source Heat Pump (GSHP). This article aims at obtaining a deeper understanding about the process of the heat transfer between the BHE and surrounding soil which is under the behavior of the groundwater seepage and suitability evaluation on development and utilization of shallow geothermal
13、 energy from the regional scale and field scale.,.Through theory analysis, the model of the borehole exchanger under conduction manners and heat infiltrates coupling manners was established with FELOW. The energy efficiency, heat transfer endurance and heat transfer in the unit depth were introduced
14、 to quantify the energy efficient and the endurance period. The performance of a BHE in soil with and without groundwater seepage was analyzed of heat transfer process between the soil and the working fluid. Basing on the model, the varied regularity of energy efficiency performance an heat transfer
15、 endurance with the conditions including the different configuration of the BHE, the soil properties, thermal load characteristic were discussed. Focus on the heat transfer process in multi-layer soil which one layer exist groundwater flow. And an investigation about thermal dispersivity was also an
16、alyzed its influence of on heat transfer performance. Evaluation of shallow geothermal energy for regional scale by using the analytic hierarchy process, Evaluation the practical working condition of shallow geothermal energy by simulation.Ultimately, some conclusions were reached as below：1.On the
17、condition of non-seepage, heat diffuse radially in the shape of circle which is easy to cause the accumulation of heat. It takes long time for Borehole exchangers to reach local thermal equilibrium (over 10 years). On the condition of seepage(110-6m/s), heat transfer through the upstream of groundwa
18、ter would be inhibited, but heat transfer through the downstream can reach a longer distance which can weaken the negative effect caused by heat accumulation and shorten the time the borehole exchangers reach the local thermal equilibrium. Meanwhile, the groundwater flow can improve the transfer eff
19、iciency of the Ground Source Heat Pump(GSHP).When the borehole exchangers run continuously ten years, its heat transfer power for per unit depth will increase 68%（060m exists seepage flow）comparing with the condition of non-seepage.2.On the condition of seepage and non-seepage, the changing of initi
20、al temperature of rock and soil mass has no effect of heat transfer efficiency. However, in terms of refrigerate condition, the lower the initial temperature, the higher the temperature difference between the import and export water of the borehole exchanger. And the time the borehole exchanger run
21、at high level will be lasting for a longer time. Lower soil temperature will be better for the running of borehole exchangers in the area where refrigeration is needed.3.If the length of borehole exchanger increased, the heat transfer power will be enhanced and the time the borehole exchanger runnin
22、g at high level will be longer, but it does not mean that the ability of heat transfer can be reinforced. Per unit of the heat transfer power is determined by the total amount of heat transfer and the depth of borehole exchanger. Before designing, we should consider the amount and the depth of the B
23、HE.4.The velocity of circulating fluid in the buried pipe must be maintained in turbulence flow. Under the premise the heat pump working in order, the quicker flow velocity, the bigger the capacity of heat transfer. But the BHE which have a large flow velocity demands more powerful circulating pumps
24、. So it is necessary for us to make a balance between the capacity and the cost, the circulating liquid rate of flow should be controlled between 35 m3/d to 45m3/d（The inner diameter of pipe is 0.031m）.5.By the thermal condition BHEs operation sustainability research, that shallow geothermal energy
25、is not sustainability , we should regrade the shallow geothermal energy as “Energy storage “ to develop.6.In the same condition, the seepage type BHEs sustainability is obviously better than thermal conductivity type BHEs sustainability.7.The borehole exchanger which is buried in multilayered rock a
26、nd soil mass, usually only exists groundwater seepage in one layer. The quicker seepage flow velocity the better for heat transferring. The modifiable Peclet number was summarized to judge the intensity of heat transfer by convection. When the modifiable Peclet number is 0.0041, the amount of heat t
27、ransfer power will increase 5% comparing with non-seepage case. And when the modifiable Peclet number is 0.1291, the amount of heat transfer power will increase 30% comparing with non-seepage case.8.According to the Thermal Response Test (TRT) with forced groundwater seepage, a contrast was given ou
28、t between the circulating temperature of the borehole exchanger and the emulation temperature value. And the area where the seepage flow exist was also investigated. The comparison result shows that the error between the emulation value and the actual value can be accepted within engineering permiss
29、ible error range. The final result proves that the model of heat infiltrates coupling model established in this context is reasonable，which can be applied to engineering design.9.According to the area of shallow geothermal energy assessment, the Fuzhou area suitable for the development and utilizati
30、on of shallow geothermal area mainly concentrated in the quaternary marine plain and residual slope area, the area are easy drilling, conductivity of aquifer, groundwater run off alternating strong.10.In Fuzhou area, at the site scale to make heat exchange system sustainable.The cold load and heat l
31、oad imbalance rate should be no more than 45%.Keywords: Borehole Exchanger (BHE); FEFLOW;Groundwater and Heat infiltrates coupling model; Suitability evaluation目 录第一章 绪论 .11.1 选题目的与意义 .11.2 国内外研究现状及分析 .31.2.1 地埋管换热器纯导热模型的研究 .31.2.2 地埋管换热器在含水层中的换热模型研究 .31.2.3 浅层地温能适宜性评价研究 .41.2.4 待解决的问题 .51.2 创新点 .51
32、.3 主要研究内容和技术路线图 .5第二章 地埋管地源热泵工作原理分析 .72.1 传热基本理论 .72.2 浅层岩土体系统热动态均衡分析 .72.2.1 浅部圈层热动态均衡分析 .72.2.2 浅部地热能资源分布及温度场分布 .82.3 饱和多孔介质的传热分析 .92.3.1多孔介质中物质和热量的输运 .92.3.2 岩土体热物性参数 .92.4 钻孔换热器内部的传热分析 .122.5 水热耦合模拟方法 .14第三章 原位热响应试验 .163.1热响应试验理论基础 .163.1.1热响应试验简介 .163.1.2 理论公式推导 .173.1.3 测试孔内传热理论 .213.1.4 热响应试验
33、传热理论 .253.2福州地区原位热响试验 .263.2.1 福州市基本概况 .263.2.2 试验区场地概况 .263.2.3 典型场地热物性参数计算 .31第四章 无渗流型地埋管地源热泵换热特征分析 .374.1 物理模型与数学模型 .374.1.1 物理模型 .374.1.2 数学模型 .374.1.3 初始条件与边界条件 .375.2无地下水渗流作用的热响应试验验证与分析 .384.3 无渗流条件下数值计算模型条件 .414.4 无渗流型地埋管地源热泵换热分析 .424.5 无渗流型地埋管地源热泵换热影响因素分析 .454.5.1地下岩土体性质的影响 .454.5.2地埋管自身特性的影
34、响 .494.6 无渗流条件下群管的换热特征分析 .544.6.1 无渗流条件下群管换热过程分析 .544.6.2 无渗流条件下群管运行的可持续性研究 .574.7 本章小结 .61第五章 渗流型地埋管地源热泵换热特征分析 .635.1 物理模型与数学模型 .635.1.1 物理模型 .635.1.2 数学模型 .635.1.3 初始条件与边界条件 .645.2 有地下水渗流作用的热响应试验验证与分析 .645.2.1 试验系统与试验流程 .665.2.2 试验结果分析 .675.3 渗流型地埋管换热器换热计算模型条件 .705.4 渗流型地埋管地源热泵换热特性分析 .705.5 渗流型地埋管
35、地源热泵换热影响因素分析 .725.5.1地下岩土体性质的影响 .725.5.2地埋管自身特性的影响 .765.6 渗流条件下下群管运行的换热特性分析 .805.7 渗流条件下系统运行的可持续性研究 .835.8 多层岩土体地埋管换热器换热特性分析 .905.9 本章小结 .94第六章 浅层地温能适宜性评价 .956.1 区域性地埋管地源热泵适宜性评价 .956.1.1区域性地埋管地源热泵适宜性分区评价的原则与依据 .956.1.2区域性地埋管地源热泵适宜性的评价 .966.1.3区域地埋管地源热泵适宜性分区评价的验证 .1016.2 场地尺度下的地埋管地源热泵适宜性评价 .1036.2.1 场地评价模拟的初始条件及换热器运行策略 .1036.2.2小型办公场地（小）负荷特性下地源热泵系统适宜性评价 .1046.2.3中型宾馆场地（大）负荷特性下地源热泵系统适宜性评价 .1086.3 本章小结 .111第七章 结论与建议 .1137.1 结论 .1137.2 建议 .114致 谢 .115参考文献 .116
