地埋管换热器动态热负荷下地层温度场的解析解

垂直地埋管换热器（borehole heat exchanger,BHE）是利用浅层地热能的主要换热装置,如何确定合理的地埋管间距对地源热泵系统（ground source heat pump system,GSHPs）的传热性能与经济性影响很大。以往工程应用中未考虑地埋管热负荷的动态变化,常采用最大延米热/冷负荷（即最不利情况下）的影响半径作为设计依据,使设计参数趋于保守,很难实现地源热泵系统的技术和经济优化,而考虑负荷变化的数值模拟方法耗时复杂,不便于工程应用。文章提出了一种在地埋管实际热冷负荷动态变化条件下,计算地埋管换热器影响半径的简单数学方法。该法首先推导了地埋管换热器在周期性热流边界条件下,井筒周围地层温度场的解析解,在此基础上将地面建筑物全年周期下的实际波动热冷负荷进行傅里叶级数近似展开,最后通过线性叠加每个周期函数对应的解析解,得到建筑物实际动态热冷负荷下的地层温度动态分布。提出的解析解实时耦合了地面建筑动态热冷负荷,计算结果接近实际应用,具有计算精度高、简单方便快捷的优点,便于在工程实际中推广应用。     

套管式地埋管换热器热短路及换热性能

套管式地埋管换热器是深层地源热泵系统常用的换热装置。基于流体流动换热方程,建立套管式地埋管换热器与周围岩体之间的传热模型。以第一个供暖季为例,分析内管导热系数和循环水流量对换热性能的影响,并引入换热器效能对热短路现象进行评估,研究结果显示:内管导热系数越大,热短路现象越显著;热短路使内外管中循环水温差降低,管内出现热堆积,导致换热器换热功率降低;套管式地埋管换热器的换热功率随循环水流量的增大逐渐增大;内外管之间存在热短路时,出口水温随循环水流量的增大先升高后降低,随着流量增大,换热器效能增大。研究成果可为深层地源热泵系统中地埋管换热器的设计提供借鉴。      

山东省鲁北地区浅层地热能资源评价

鲁北地区于2001年已陆续开始应用热泵技术开发浅层地热能,但区内的浅层地热能资源评价工作却严重滞后,制约了区内浅层地热能资源的开发和合理利用。为促进鲁北地区浅层地热能的开发利用,省政府拿出专项资金,开展了鲁北地区浅层地热能的资源评价工作,前期在调查区域内开发利用现状和摸清地质条件的基础上,采用层次分析法,分别对地下水换热方式和地埋管换热方式进行了开发利用适宜性分区,采用热储体积法对该区的浅层地热容量进行了计算,得出鲁北地区浅层地热容量为29．386×10^15 kJ/℃;并根据适宜性分区结果,分别对地下水式和地埋管式地源热泵适宜区、较适宜区可利用换热量也进行了计算,得出地下水式地源热泵200 m以浅可利用换热量为0．8489×10^10kW·h,地埋管式地源热泵200m以浅可利用换热量为6．5261×10^12kW·h。     

Effect of thermal-hydrogeological and borehole heat exchanger properties on performance and impact of vertical closed-loop geothermal heat pump systems

Ground-source geothermal systems are drawing increasing attention and popularity due to their efficiency, sustainability and being implementable worldwide. Consequently, design software and regulatory guidelines have been developed. Interaction with the subsurface significantly affects the thermal performance, sustainability, and impacts of such systems. Reviewing the related guidelines and the design software, room for improvement is evident, especially in regards to interaction with groundwater movement. In order to accurately evaluate the thermal effect of system and hydrogeological properties on a borehole heat exchanger, a fully discretized finite-element model is used. Sensitivity of the loop outlet temperatures and heat exchange rates to hydrogeological, system and meteorological factors (i.e. groundwater flux, thermal conductivity and volumetric heat capacity of solids, porosity, thermal dispersivity, grout thermal conductivity, background and inlet temperatures) are analyzed over 6-month and 25-year operation periods. Furthermore, thermal recovery during 25  years after system decommissioning has been modeled. The thermal plume development, transport and dissipation are also assessed. This study shows the importance of subsurface thermal conductivity, groundwater flow (flux > 10^?7 m/s), and background and inlet temperature on system performance and impact. It also shows the importance of groundwater flow (flux > 10^?8 m/s) on thermal recovery of the ground over other factors.     

不同土壤类型与含水率对水平埋管换热性能影响数值分析

为揭示地源热泵系统水平埋管换热器在不同土壤类型中的换热性能,基于土壤毛管水理论知识,结合数值模拟的研究手段,探讨了蓄能不同类型土体内(砂土、壤土、黏土)三相组成的差异对水平埋管换热器换热特性的影响规律。结果表明,在通入308.15 K制冷工况下,水平管在壤土中的出水温度降低至303.3 K,进出口水温差为4.9 K,埋管单位延米换热量37.1 W/m,水平管在壤土中的制冷换热效益显著;不同土壤(砂土、壤土、黏土)在经历相同制冷周期下,水平管的换热过程对壤土的温度场分布影响最小,管体在壤土中运行时热堆积风险系数最低。研究表明,水平管与土壤的换热性能同时受土壤比热容与土壤导热系数的影响,提高土壤导热系数比提高土壤比热容获得的效益更加显著。可以通过压实回填、减少土壤孔隙率、提高固相回填材料导热系数、加大布管深度以提高回填材料含水率等方法来强化埋管的换热性能。      

花岗岩粗糙单裂隙对流换热特性的数值模拟

在干热岩储层中开采地热能,往往需要对储层进行人工水力压裂以形成贯穿的换热通道。然而,热储中的对流换热对干热岩的采热率有重要影响,经过人工刺激的储层会形成几何形态各异的裂隙面,而裂隙粗糙程度的不同则会引起换热性能的显著差异。因此,选取4条Barton的经典岩石裂隙粗糙度曲线,在试验室条件下建立一个单裂隙对流换热模型。详细分析了花岗岩粗糙裂隙中热工质的换热特性。结果表明：局部对流换热系数沿着裂隙长度方向逐渐降低;节理粗糙系数JRC值越大,平均对流换热系数就越大,表明换热性能越好;局部对流换热系数的分布与JRC曲线的几何轮廓形态有很好的相关性,波峰波谷的变化趋势相一致;相对于温度而言,高流速对局部对流换热系数具有放大效应,流速越大,局部对流换热系数波动越大。     

中深层地热单井换热数值计算

中深层地热单井换热是一种"取热不取水"开发地热能的技术,该技术具有不破坏地下水环境、取热量大等优势,但目前就深度3 000 m以上的单井换热数值计算研究较少,本文针对西安地区地热地质条件,采用数值法计算了不同井型结构（L型定向井、丛式定向井）的中深层地热单井在连续运行一个采暖季情景下的换热量。计算结果表明:同一流速及地温梯度下,在系统连续运行120 d后,L型定向井的出口温度、单位时间取热量及延米取热量高于丛式定向井;同一流速下,地温梯度越大其出口温度越高,单位时间取热量及延米取热量也越大;同一地温梯度下,流速越大其出口温度越低,单位时间取热量及延米取热量越大。丛式定向井井斜30°的出口温度、单位时间取热量及延米取热量高于井斜45°,随着流速的增加,两种井斜下的出口温度、单位时间取热量及延米取热量的差异逐渐减小。从出口温度、单位时间取热量及延米取热量角度考虑,L型定向井的换热效率优于丛式定向井;从钻井施工的难易程度角度考虑,丛式定向井优于L型定向井;丛式定向井的两种井斜结构中,井斜30°的丛式定向井优于井斜45°。所得不同工况的计算结果,可为中深层地热的开发与利用提供参考依据。      

深层垂直井同轴换热能力数值模拟分析

针对中深部（1 500~4 000 m）地热资源深井同轴“保水取热”科学评价问题,以COMSOL Multiphysics多物理场耦合数值计算软件为模拟平台,构建垂直单井岩-水耦合传热模型,以西安地区地层与地温特征为模拟背景,计算分析2种地温梯度（0.027、0.030℃/m）与4种注水口流速（0.25、0.50、0.75、1.00 m/s）工况下深层（3 500 m）地热单井套管换热能力。同时,建立5种井间距下的群井数值模型,分析不同井间距下群井中心井的出口温度变化规律。模拟结果显示:地温梯度越大,进出口温差越大,单位时间换热量与单位延米换热量越大;入口注水流速越大,进出口温差越小,但单位时间换热量与单位延米换热量越大,即地温梯度、流速越大,深层垂直钻孔套管换热的效率越高;西安地区3 500 m井深工况下,相邻地热井的间距为30 m时能够保证其地层温度不会相互干扰。研究结论可为深层地热开发利用提供科学参考。移动阅读      

地埋管热泵换热系统热影响半径分析

地埋管热泵换热系统是一种在开发利用浅层地热能过程中应用非常广泛的热交换系统。本文依托山东省国土资源厅实施的聊城市浅层地温能调查评价项目,对聊城市某小区内的地埋管热泵换热系统安装温度自动采集监测装置,2016年采集一个完整制冷期的地温变化数据,通过监测地埋管热泵系统换热孔和周边一定距离内监测孔内温度变化,绘制换热孔和监测孔一定时间范围内温度随时间和距离的关系变化曲线,分析换热孔在吸收热量后温度通过土壤介质的传播速率和最大影响半径,从而为实际地埋管热泵换热系统工程设计提供了依据。     

中深层地热井下同轴换热器长期换热性能研究

中深层地热井下同轴换热器具有取热量大、出口水温高的特点,近年来受到供热行业的高度关注。目前的研究主要是对单个供热周期内的中深层地热井下同轴换热器的换热性能进行分析,缺乏对其长期换热性能的相关研究。本文根据中深层地热井下同轴换热器供暖季供热、非供暖季停歇运行的特点,基于能量守恒方程建立换热器的数值换热模型,并采用有限体积法对模型进行离散,通过Matlab平台数值分析其在长期运行过程中换热性能的变化规律。结果表明:换热器的换热性能随着运行年份逐渐下降,且下降程度逐年减小,最终达到准稳态。其中,次年平均换热量的下降比例最大,且换热器埋深越大,换热量的下降比例越小。埋深为2 000、2 500、3 000 m换热器的次年平均换热量的下降比例依次为4.00%,3.78%和3.56%,第30年的平均换热量较第1年分别下降13.7%、13.1%、12.4%。岩体温度逐年下降,其受干扰半径逐年增加。在30 a运行期间,埋深2 000 m的换热器在每年供热季结束时的岩体温度受干扰半径从13 m增加至105 m。此外,换热器深度越大,其周围岩体温度受干扰半径越大。本研究结果阐明了中深层地热井下同轴换热器在长期取热过程中换热性能的变化规律,对换热器长期取热的设计具有指导意义。      

基于高导热材料填充漏失构造的深井换热器性能分析

地热供暖可有效缓解北方雾霾天气。干热岩虽然储量丰富,但增强型地热技术由于开发费用较高,裂隙控制以及避免诱发地震的技术尚不成熟,现阶段还不能商业化应用。水热型地热开发技术虽较成熟,但受资源条件的限制,开发规模较小。对于大多地区,受地质构造和资源禀赋的控制,单井产水量较低或者回灌难,开发经济效益较差。深井换热器(DBHE)技术是开采地热水低产区或回灌难地区热能的有效方式,但受制于岩石导热系数低,单井输出功率小,投资回收期长。为提高DBHE的输出功率,本文提出了增强型深井换热器(EDBHE),通过主动将高导热性能的复合填充剂流进漏失构造的方式提高岩石的导热性能,通过调节回压、密度和黏度来控制漏失量。研究结果表明,单井EDBHE十个采暖季的平均取热功率为1002.34 kW,是DBHE(424.45 kW)的2.36倍。而双井EDBHE十个采暖季的平均取热功率更是达到了27501.61 kW,且热输出稳定,每年的衰减率0.95%。EDBHE技术有效利用了出水量低或回灌难的水热型热储,大幅提高了其出力,扩大了地热供暖的应用范围。     

Research on the characteristics and influencing factors of terrestrial heat flow in Guizhou Province

Terrestrial heat flow is an important physical parameter in the study of heat transfer and thermal structure of the earth and it has great significance in the genesis and development and utilization potential of regional geothermal resources. Although several breakthroughs in geothermal exploration have been made in Guizhou Province. The terrestrial heat flow in this area has not been properly measured, restricting the development of geothermal resources in the province. For this reason, the terrestrial heat flow in Guizhou was measured in this study, during which the characteristics of heat flow were determined using borehole thermometry, geothermal monitoring and thermal property testing. Moreover, the influencing factors of the terrestrial heat flow were analyzed. The results show that the thermal conductivity of rocks ranges from 2.0 W/(m·K) to 5.0 W/(m·K), with an average of 3.399 W/(m·K); the heat flow varies from 30.27 mW/m² to 157.55 mW/m², with an average of 65.26 ± 20.93 mW/m², which is slightly higher than that of the average heat flow in entire land area in China. The heat flow in Guizhou generally follows a dumbbell-shaped distribution, with high values present in the east and west and low values occurring in the north and south. The terrestrial heat flow is related to the burial depths of the Moho and Curie surface. The basaltic eruptions in the Emeishan led to a thinner lithosphere, thicker crust and lateral emplacement, which dominated the basic pattern of heat flow distribution in Guizhou. In addition, the dichotomous structure of regional active faults and concealed deep faults jointly control the heat transfer channels and thus influence the terrestrial heat flow.     

胶东半岛不同构造单元深部热流分流聚热模式

中生代、新生代时期地壳剧烈运动将胶东半岛划分为胶北隆起、胶莱凹陷、胶南-威海隆起三大构造单元,其中隆起山地区广泛分布花岗岩、变质岩,凹陷盆地区主要分布砂岩沉积地层,胶北隆起区与威海隆起区相对于胶莱凹陷盆地区具有更高的大地热流值.为系统分析胶东半岛大地热流值分布特征及其形成机理,本文在分析胶东半岛构造-热发展史、地热地质...     

可再生浅层地热能资源开发利用关键技术问题

浅层地热能开发利用是一门多学科的综合技术,涉及地质、钻探、热交换、制冷、暖通空调、建筑材料学等多学科的知识,其关键技术问题是岩土体的热性能测试、地下换热器的优化设计、地下水渗流对地下管换热性能的影响、地下热交换场特征、浅层地热能分布规律及开发利用方式。只有在解决上述关键技术问题的基础上,进行科学规划、合理开发、优化设计,才能使该行业步入健康发展的轨道。     

Estimation of groundwater flow from temperature monitoring in a borehole heat exchanger during a thermal response test

To estimate the groundwater flow around a borehole heat exchanger (BHE), thermal properties of geological core samples were measured and a thermal response test (TRT) was performed in the Tsukuba upland, Japan. The thermal properties were measured at 57 points along a 50-m-long geological core, consisting predominantly of sand, silt, and clay, drilled near the BHE. In this TRT, the vertical temperature in the BHE was also monitored during and after the test. Results for the thermal properties of the core samples and from the monitoring indicated that groundwater flow enhanced thermal transfers, especially at shallow depths. The groundwater velocities around the BHE were estimated using a two-dimensional numerical model with monitoring data on temperature changes. According to the results, the estimated groundwater velocity was generally consistent with hydrogeological data from previous studies, except for the data collected at shallow depths consisting of a clay layer. The reasons for this discrepancy at shallow depths were predicted to be preferential flow and the occurrence of vertical flow through the BHE grout, induced by the hydrogeological conditions.     

地热储层单裂隙岩体渗流传热数值模拟研究

研究地热储层裂隙岩体中的渗流传热过程对干热岩地热资源的开采具有重要的意义。本文以干热岩地热工程为背景,采用COMSOL Multiphysics数值模拟软件对地热储层单裂隙岩体中渗流传热机理进行了研究,并分析了流体注入速度和温度对岩体温度场的影响及其对干热岩地热工程的影响。研究发现流体参数对岩体温度场的影响主要体现在两个方面：一方面是对岩体温度场受扰动区域以及幅度的影响,另一方面是对岩体温度场达到稳态所需要时间的影响。流体注入速度的提升会降低系统的寿命和寿命期的出口法向总热量值,当考虑出口法向总热通量时,存在最佳流体注入速度,本研究中最佳流体注入速度为0.011m/s。流体注入温度的提升会增加系统的寿命和系统的出口法向总热通量和总热量。研究为干热岩自热资源的开发与利用提供了理论依据,为工程运行参数的设计提供了参考依据。     

热交换桩的作用机制及其应用

将常规桩与地源热泵技术结合起来形成了一种新型基桩--热交换桩。首先介绍了热交换桩的概念和工作机制,并对其进行了总结和分类。桩体中埋设换热器并与地表管路连接,通过换热器中的交换液体与桩体、桩周土-地基土及地下水系统进行热交换,形成封闭的地源热泵的地热交换器,使得热交换桩具有常规基桩和地源热泵预成孔直接埋设换热器的双重作用。最后分析了热交换桩目前国内外的应用现状,指出了实际应用关键技术问题及其研究的方向。分析后可以看出,热交换桩是一种经济、环保、节能的新技术,值得推广使用。     

中深层套管换热器短期无干扰名义取热量计算解析方法

从地下传热基本原理出发,考虑地温梯度影响,建立了中深层套管换热器进出口流体平均温度解析解和长时间近似解,推导了中深层套管换热器短期无干扰名义取热量计算解析公式,并通过与文献中结果对比进行了验证。研究结果表明,中深层套管换热器短期无干扰名义取热量是地温梯度的线性函数。短期无干扰名义取热量计算解析公式简单实用,可以实现中深层套管换热器短期换热性能快速评价。     

地埋管换热器钻孔长度计算方法研究

地埋管换热器钻孔长度计算是土壤源热泵系统设计的核心。为规范地埋管换热器钻孔长度计算,从《地源热泵系统工程技术规范》基本要求出发,以合肥市某土壤源热泵工程为例,进行了地埋管换热器钻孔长度计算和校核模拟计算。研究表明,热干扰对地埋管换热器钻孔长度有较大的影响,不考虑热干扰影响的钻孔长度计算结果偏小;由于热堆积的影响,地埋管换热器流体平均出口温度呈现逐年上升趋势。校核模拟计算结果表明地埋管换热器钻孔计算长度能够满足规范的要求。     

Discussion on heat source mechanism and geothermal system of Qinghai Gonghe-Guide Basin

The Qinghai Gonghe-Guide Basin together with the alternatively distributed mountainous region shows characteristics that the conductive geothermal resource of the basin has high geothermal gradient, the granite occurs in the bottom of borehole for geothermal exploration, and the convective hot springs in the basin-edge uplift fracture are in zonal distribution and with high-temperature geothermal water. There are still some divergences about the heat source mechanism of the basin. In this paper, queries to the view of mantle-derived heat source have been put forward, coming up with geochemical evidences to prove that the radiogenic heat of granite is the heat source within the mantle. Additionally, temperature curve is drawn based on the geothermal boring and geochemical geothermometer has been adopted for an estimation of the temperature and depth of the geothermal reservoir, it has been found that the surrounding mountains belong to the medium-temperature geothermal system while the area within the basin belongs to the high-temperature geothermal system with the temperature of borehole bottom reaching up to 175-180 ℃. In this paper, discussions on the problems existing in the calculation of geothermal gradient and the differences generated by the geothermal system have been carried out.