竖直埋管地热换热器钻孔内的传热分析

准三维模型为竖直埋管地热换热器的结构优化提供了较为精确的理论基础。利用准三维模型对竖直埋管地热换热器进行分析与研究得出，不同的行程布置对双U型埋管地热换热器的传热性能有较大影响。就钻孔内热阻的对比，双U型埋管比单U型埋管钻孔内的热阻低，因而双U型埋管地热换热器较单U型埋管地热换热器更为合理。     

地源热泵系统施工技术

推广地源热泵技术对建筑供热和空调系统的节能有重要意义，经济合理地设置地热换热器是应用地源热泵技术的关键。重点介绍了竖直埋管地热换热器施工技术，特别对地热换热器的钻孔、下管和回填的技术要点和设备进行了详细阐述。     

地源热泵竖直埋管换热器的设计

本文论述了地源热泵竖直埋管换热器的设计方法,重点阐述了地热换热器各部分的设计要点,主要包括地热换热器设计中的类型选择、平面布置、埋管的管径与长度、埋管的连接方式、回填材料及循环液的选取等。     

竖直埋管地热换热器的设计

为优化地热换热器的设计，利用地源热泵地热换热器设计专用软件，结合实际工程，对竖直U型埋管地热换热器设计的不同方案作了比较，对主要影响因素进行了分析，从技术和经济两方面阐明了地热换热器设计时应考虑的主要因素及设计方法。     

竖直埋管地热换热器的设计

为优化地热换热器的设计，利用地源热泵换热器设计专用软件，结合实际工程，对竖直U型埋管地热换热器设计的不同方案作了比较，对主要影响因素进行了分析，从技术和经济两方面阐明了地热换热器设计时应考虑的主要因素及设计方法。     

地热换热器U型埋管的传热模型及热阻计算

讨论了地源热泵地热换热器竖直U型埋管钻孔内的二维稳态传热模型。基于钻孔内的温度场的二维解析解，得出钻孔热阻表达式。分析了影响钻孔热阻的几个相关因素，通过与一维简化模型得到的钻孔热阻相比较，认为采用二维模型可以为工程设计提供更准确可靠的热阻数据。     

竖直双U型埋管地热换热器支管间热短路分析

采用地热换热器准三维传热模型和数值计算的方法,对竖直双U型埋管地热换热器支管间的热短路进行了分析,讨论了管间距和回灌材料的导热系数对热短路的影响,并提出了减少热短路的措施。     

形状因子法在垂直U型埋管传热分析中的应用

竖直U型埋管热交换器是地源热泵系统的重要组成部分。文章以能量平衡为基础,采用传热学中的形状因子法,针对某一常用结构形式的地埋管换热器热阻和换热量进行了数值计算。在此基础上,重点分析了钻孔深度、孔内的管间距、地埋管进水温度和土壤温度对换热器热阻和换热性能的影响,旨在为竖直U型地埋管换热器的设计和工程应用提供必要的参考。     

土壤源热泵竖直埋管换热器钻孔外传热模型综述

介绍了土壤源热泵竖直埋管换热器钻孔外的传统的无限长线热源模型,无限长圆柱模型,有限长线热源模型以及改进后的热湿传递的线热源模型,变热流的线热源模型,土壤分层的线热源模型。分析了各种模型之间的联系、区别以及优缺点。提出了完善土壤源热泵竖直埋管换热器钻孔外传热模型需进一步研究的内容。     

连续与间歇运行工况下地埋管换热器的换热特性研究

为了研究地埋管换热器在变负荷下连续运行与间歇运行的换热性能,基于有限长线热源渗流模型建立竖直地埋管钻孔外准三维非稳态传热模型,应用叠加原理计算钻孔群中钻孔壁温度场及地埋管内流体温度场。在存在地下水水平渗流的情况下,研究了变负荷连续运行模式下不同渗流速度、不同运行工况及不同钻孔位置对地埋管换热器的换热性能的影响。结果表明,在连续运行模式下,边缘位置的钻孔及较大的渗流速度能够增强地埋管换热器的换热性能;在间歇运行模式下,地埋管换热器的运行份额越小,其制冷效果越好,反之,制冷效果越差;在间歇运行工况下,土壤温度能在系统间歇期内得到一定程度的恢复,从而更好地提高地热能的利用率。     

Efficiency of Vertical Geothermal Heat Exchangers in the Ground Source Heat Pump System

Taking the fluid temperature distribution along the borehole depth into account, a new quasi-three-dimensional model for vertical ground heat exchangers has been established, which provides a better understanding of the heat transfer processes in the geothermal heat exchangers. On this basis the efficiency of the borehole has been defined and its analytical expression derived. Comparison with the previous two-dimensional model shows that the quasi-three-dimensional model is more rational and more accurate to depict the practical feature of the conduction of geothermal heat exchanger, and the efficiency notion can be easily used to determine the inlet and outlet temperature of the circulating fluid inside the heat exchanger.     

地源热泵竖直埋管的有限长线热源模型

对地热换热器竖直埋管的非稳态传热模型进行了分析讨论。采用虚拟热源和格林函数法给出了半无限大介质中有限长线热源产生的非稳态温度场的解析解表达式。与稳态温度场的解进行比较,讨论了温度场达到名义上的“稳态”所需的时间,同时对于达到稳态时的温度场也进行了分析,指出了现行教科书中关于该问题的错误,提出了稳态时两个地热换热器孔壁代表性温度的定义,并对两者进行了比较,进而给出了可供工程应用的简化计算公式,并对两者进行了比较,进而给出了可供工程应用的简化计算公式。基于以上分析,进一步讨论了全年冷热负荷不平衡对地热换热器长期性能的影响。     

利用地下水填充钻孔的埋管换热器性能分析

地下水填充的井下换热器（GFBHE）是一种不需要灌浆,利用地下水填充钻孔进行换热的地热换热器。针对GFBHE建立了瞬态三维数值模型进行模拟,并与利用普通灌浆材料进行回填的埋管换热器进行对比。数值模型通过将孔隙型岩层等效为饱和多孔介质的方法将钻孔外部的自然对流现象考虑在内。研究了包括渗透系数、地温、钻孔孔径在内的关键因素对GFBHE性能的影响。结果表明,当含水层渗透系数大于1×10^-4 m/s时,GFBHE性能明显优于利用灌浆填充钻孔的地热换热器,在富水区域利用GFBHE取代后者是可行的。GFBHE的换热性能随着钻孔孔径、含水层渗透性的增大以及地温的升高而提升。     

深层地埋管换热器换热性能模拟及稳定性研究

以深层地源热泵地埋管换热器为研究对象,对其换热特性进行数值模拟和实验研究。建立考虑轴向地温梯度的深层地埋管换热器传热模型并进行模拟计算,通过示范工程现场测试数据验证该模型的正确性。对深层地埋管换热器换热的性能稳定性进行研究,发现深层地埋管换热器连续长期运行及间歇长期运行下换热性能基本稳定。当按不同运停比运行时,岩土温度恢复效果良好。研究结果表明深层地源热泵有较好的换热性能及运行稳定性,为深层地热能的开发利用提供了新思路。     

Heat exchanger optimization for geothermal district heating systems: A fuel saving approach

One of the most commonly used heating devices in geothermal systems is the heat exchanger. The output conditions of heat exchangers are based on several parameters. The heat transfer area is one of the most important parameters for heat exchangers in terms of economics. Although there are a lot of methods to optimize heat exchangers, the method described here is a fairly easy approach. In this paper, a counter flow heat exchanger of geothermal district heating system is considered and optimum design values, which provide maximum annual net profit, for the considered heating system are found according to fuel savings. Performance of the heat exchanger is also calculated. In the analysis, since some values are affected by local conditions, Turkey's conditions are considered.     

Numerical and experimental study of transient conjugate heat transfer in helical closed-loop geothermal heat exchangers for application of thermal energy storage in backfilled mine stopes

The geothermal potential available from deep underground mines has yet to be utilized. However, stope-coupled heat exchangers (SCHE) are aiming to take advantage of the unused low-grade geothermal energy. Backfilled stopes provide a unique opportunity to install nonlinear heat exchangers, as the geometry is not limited to the shape of a borehole. Helical pipes deliver superior fluid mixing and heat exchange compared to straight pipes, due to the effect of the secondary flow within the helical pipe. The helical closed-loop geothermal heat exchanger enables the backfilled stopes of the mine to be repurposed as thermal energy storage units. This article delves into the experimental results from a unique state-of-the-art laboratory scale helical closed-loop heat exchanger with varying thermophysical parameters. Additionally, a novel conjugate numerical model is developed and its results are validated against the base case of the experimental studies. Additionally, the numerical model is validated in a spatial-temporal sense with thermocouple data from the experimental rig. The numerical model is also applied to a helical SCHE situated within a backfilled stope for the first time. The results of the numerical model suggest that the pumping rate through the SCHE has a significant effect on the heat exchange rate and the overall energy transfer between the SCHE and the backfill. Additionally, the temperature contours from the numerical model suggest that a decreased pitch/helical diameter will increase the storage capacity of the helical SCHE. Overall, an average of 2.5 MW can be stored over the first 4 days of geothermal charging with the investigated full-scale SCHE, boasting a pseudo-steady-state storage rate of 1.7 MW.     

中深层同轴换热器充填材料热性能研究

地热能作为分布广、储量大的可再生能源,在节能减排和促进碳中和方面具有重要作用。同轴换热器在开采中深层岩土体热量方面优势明显,可以进行无干扰式“取热不取水”开发。作为换热器与地层岩土体的传热媒介,充填材料对热性能的影响至关重要。采用数值模拟方法分析5种充填材料对流体温度、岩土体温度和作用范围的影响。结果表明,充填材料水的热阻是细砂-膨润土的1.5倍;采用高导热的充填材料（细砂-膨润土）后,出口流体温度升高了1.81℃,环空流体随深度增加呈非线性演化;换热器短期（4个月）和长期（20年）运行模式下井底（2 000 m）影响范围分别是深度500 m的1.5倍和7倍;细砂-膨润土作为充填材料的换热器在短期和长期运行模式下,井底影响范围可分别达到5.2 m和36.5 m。     

Thermal analysis of indirect geothermal district heating systems

Low- and moderate-temperature geothermal resources have been discovered in many areas of the world, and are being used increasingly for district heating. Due to the corrosive action of some geothermal waters, heat exchangers are used to avoid circulating the geothermal fluid directly through the district heating systems, in what are called Indirect Geothermal District Heating Systems (IGDHS). In this case, the geothermal water acts as a heat source directly heating the network fluid through a heat exchanger. However, it is different from that of conventional systems in which hot water from a fossil fuel boiler is used directly. In the former (IGDHS), the geothermal water is regarded as a heat source with constant temperature, and in the latter the boiler is considered a heat source with variable heat flux. This paper presents a thermal analysis of a simple IGDHS, and discusses the selection of heat exchangers and optimum operating conditions.     

单U、双U型埋管换热器换热性能与经济性研究

结合实际工程建立单U型与双U型埋管换热器实验系统,进行夏季排热和冬季取热实验。以单位井深换热量为评价指标对不同埋管方式的换热性能进行分析比较,得出排热和取热工况下,双U型埋管单位井深换热量均高于单U型。同时,分析了单U与双U型埋管换热器的经济成本构成,采用投资成本指标、静态投资成本差值和投资成本比数等参数,从换热性能和经济成本两方面对地下埋管换热器进行综合评价。