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为了确定地源热泵工程中地埋管换热器管群的最优排列方法和管间距,建立了热渗耦合下的地埋管换热器管群三维传热模型。利用Fluent软件通过数值方法模拟了不同排列方法、不同管间距下的换热器出水口温度,着重研究了存在地下水渗流时管群排列方法对换热能力的影响,并且提出了管群单位面积换热量这一评价指标。研究结果表明,叉排管群的换热能力要高于顺排管群,地下水的渗流作用使之更加明显。无论是叉排还是顺排,管群的换热能力都和地下水渗流方向密切相关。 相似文献
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为研究单U和双U地埋管换热器运行性能的影响因素,运用能耗模拟软件TRNSYS建立地埋管换热器模型对其运行特性进行仿真模拟后,与实际工程数据对比,验证模型有效性,继而以换热器能效系数为评价指标,分别对钻孔深度、U型管两管间距和回填材料导热系数等影响因素进行分析研究,得到:双U地埋管换热器的单位延米换热量为106.72 W/m,单U地埋管换热器的单位延米换热量为86.39 W/m;适当增加钻井深度、埋管间距和回填材料导热系数对整体换热效果有促进作用,且在双U埋管情况下促进作用更显著的结论. 相似文献
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本文用数值的方法对地源热泵系统中垂直单U形地埋管换热器的稳态导热进行了计算,通过对不同管材和不同U管间距的计算,发现管材的导热系数对整个传热影响较大,且两U形管之间的间距增大会强化换热。经对数值计算结果与相应设计规范的比较发现,设计规范推荐公式可满足换热需要。 相似文献
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结合岩土热响应试验,对岩土初始平均温度和综合导热系数的不同获取方法进行对比分析,结果表明无功循环平均温度及现场热响应试验得出导热系数值作为系统设计参数更为接近实际工况。分析对比不同埋管形式、不同管径的地埋管换热器换热性能,换热器采用单U形式时,DN40管较DN32管的换热性能提高约30%;不同换热器形式,DN32双U管换热性能较单U管提高约80%;DN32双U换热器的换热能力较单U40提高近40%。DN32双U换热器的换热能力远远优于其单U换热器和DN40单U换热器,可作为实际工程中优先选用的埋管形式。 相似文献
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为改善竖直地埋管换热性能,提高钻井换热效率和减少热回流损失,提出多供一回中心回水管竖直埋管形式。使用Gambit软件建立单U、双U及多供一回竖直埋管换热器与周围岩土体换热的物理模型并进行网格划分,用Fluent软件进行数值计算,对比分析不同流速下单U、双U及多供一回中心回水管竖直埋管换热器的换热性能,结果表明:多供一回换热器换热效果较单双U有较明显提高;在适宜流速下多供一回换热器可代替单双U换热器;多供一回换热器更适合间歇运行工况。 相似文献
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Huai Li Katsunori Nagano Yuanxiang Lai 《International Journal of Heat and Mass Transfer》2012,55(15-16):4404-4414
A spiral heat exchanger was applied in a ground source heat pump (GSHP) system that is primarily used for residential indoor heating. Studies that have been performed on the heat transfer of spiral heat exchanger have focused on field measurements and numerical analysis; however, theoretical research on the subject is absent in the literature. In this study, a methodology is proposed to analyze the heat performance of a spiral heat exchanger. A ring source model was established and solved analytically to describe the temperature variation of the ground caused by a spiral heat exchanger. The validity of the model was examined by an experiment on the soil temperature variation with a spiral heater. The virtual ring tube surface temperature response of unit ring circle was calculated by a superposition of the contributions of the ring source itself and adjacent ring sources. Furthermore, a fast algorithm was created to compute the average tube surface temperature resulting from the dimensionless temperature rise at a point far from the ring source that is constant when the non-dimensional distance is less than 0.13. The author confirmed that the calculation time of this proposed algorithm decreased by a factor of 100 compared with the traditional integration method. A system designer will find this algorithm helpful when determining the size of a heat exchanger under a required heating load, particularly for different arrangement of spiral heat exchangers. 相似文献
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V. R. Tarnawski 《国际能源研究杂志》1989,13(2):137-148
A one-dimensional model of ground heat storage is used to simulate complex heat and moisture processes in the vicinity of double-and single-layer ground heat exchangers. Simulated results indicate that a ground heat pump with the double-layer heat exchanger has certain advantages over the single-layer system in terms of a higher seasonal performance factor, smaller ground area, and reduced ecological risk in the soil subsurface region. Solar energy injection into the ground improves the seasonal performance factor both in the single and in the double layer heat exchanger system. Latent heat released by the freezing of soil moisture is an important component in the total amount of heat extracted from the ground when a phase change takes place. 相似文献
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The imbalance of heat extracted from the earth by the underground heat exchangers in winter and ejected into it in summer is expected to affect the long term performance of conventional ground source heat pump (GSHP) in territories with a cold winter and a warm summer such as the middle and downstream areas of the Yangtze River in China. This paper presents a new multi-function ground source heat pump (MFGSHP) system which supplies hot water as well as space cooling/heating to mitigate the soil imbalance of the extracted and ejected heat by a ground source heat pump system. The heat transfer characteristic is studied and the soil temperature around the underground heat exchangers are simulated under a typical climatic condition of the Yangtze River. A three-dimensional model was constructed with the commercial computational fluid dynamics software FLUENT based on the inner heat source theory. Temperature distribution and variation trend of a tube cluster of the underground heat exchanger are simulated for the long term performance. The results show that the soil temperature around the underground tube keeps increasing due to the surplus heat ejected into the earth in summer, which deteriorates the system performance and may lead to the eventual system deterioration. The simulation shows that MFGSHP can effectively alleviate the temperature rise by balancing the heat ejected to/extracted from underground by the conventional ground source heat pump system. The new system also improves the energy efficiency. 相似文献
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地热能作为一种非碳基能源,具有储量丰富、清洁可再生等特点,开发利用地热能有助于碳达峰的实现。在中深层地源热泵领域,我国主要以单井同轴管为主,而相对高效的中深层地热U型井地埋管案例屈指可数。为了了解中深层地热U型井地埋管换热性能及井下换热参数变化,完成了新型的U型井地埋管换热器工程,并在此基础上进行了实验研究。首先,开展了地温测量,确定了研究区的地层温度,根据热储的物性条件选取了水平井段及对接位置;其次,分析空载循环试验工况下循环水的流量及井下温度的变化情况,研究了负载工况下供回水温度、流量、换热量、不同井段对换热的贡献率、井下温度的动态变化、U型井的恢复能力等因素。实验结果表明,中深层U型井地埋管换热器井底温度会随运行时间增长而降低,流量大且回水温度较低的情况下,换热器的换热量比较高,最高为1336.8kW;回水井对换热量的增加有限,每百米增加0.12℃,实际工程中可以考虑减小口径,降低建设费用。U型井地埋管换热器的地温恢复能力较强,停止运行24h左右井底温度与初始温度差为-13℃。研究结果有助于研究人员对中深层U型井地埋管换热器有更进一步的认识,从而推动中深层地热能的健康可持续发展。 相似文献
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《Applied Thermal Engineering》2007,27(2-3):430-441
This paper presents the results of experimental measurement and numerical simulation of the performance of a heat pump system designed to make use of rainwater and ground as heat sources/sinks. The system was tested under laboratory conditions. A refrigerant was circulated through a closed loop heat exchanger to transfer heat between the heat pump and rainwater in a storage tank and another heat exchanger made of solid bars or heat pipes to transfer heat between the stored rainwater and surrounding soil. Physical and thermal properties of soil such as water content, density, specific heat, thermal diffusivity and thermal conductivity were determined. Numerical simulations were also carried out for a rainwater storage tank installed under ground for domestic application of the heat pump with different operating modes, heating loads and the sizes and types of heat exchanger. 相似文献
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Huai Li Katsunori Nagano Yuanxiang Lai 《International Journal of Heat and Mass Transfer》2012,55(23-24):6819-6831
Groundwater flows at approximately 1–3 m under the ground surface in a given region. If groundwater flow is present, the performance of a horizontal ground heat exchanger (HGHE), buried in a shallow trench, is enhanced. Nevertheless, owing to the general depth at which groundwater is present, research regarding the heat transfer of a ground heat exchanger (GHE) under conditions with groundwater flow has mainly focused on vertical GHE systems. To the authors’ knowledge, no such studies have addressed HGHEs. From a system design perspective, a prediction tool is needed to consider the groundwater flow, optimize the size of the horizontal heat exchanger, minimize the initial cost and maximize the operational efficiency. Therefore, in this study, a moving ring source model was established and solved analytically to describe the temperature response of a spiral heat exchanger with groundwater flow. In addition, experiments were carried out to study the soil temperature variation during the operation of a spiral heater with different water velocities. The validity of the proposed model was proven by the good agreement between the experimental and calculated results. The average virtual tube surface temperature variations of single ring sources in two different configurations are discussed. Furthermore, the average virtual tube surface temperatures of multiple ring sources extending from single arrangements were computed and approximation algorithms were introduced to reduce the calculation time. The approximation approach has been proven to run thousands of times faster than the initial method, and the calculation results are in 97% agreement with those of the initial method. In summary, this study provides a useful tool for the design of spiral heat exchangers. 相似文献
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为探究相变温度对相变材料回填地埋管换热器传热性能的影响,建立管内流体换热、回填区域相变换热及土壤换热的三维耦合传热数值模型,利用焓-多孔介质模型对相变区域相变问题进行处理,研究夏季间歇运行工况下不同相变温度回填材料对埋管换热器传热性能的影响。结果表明:添加PCM,可有效提高换热量,短期内缓解埋管周围热积聚,利用相变温度18℃的PCM回填,单位井深换热量至少比普通材料回填提高49.54%;在间歇运行初期,换热量随相变温度的升高逐渐减小,低相变温度的PCM可明显改善埋管换热量,但随着时间的进行,较高相变温度PCM回填对换热器换热量的改善效果优于前期低相变温度。此外,在运行期间,不同相变温度的PCM表现出不同的熔化、凝固特性,当PCM的熔化、凝固过程交替进行时,可减缓土壤温度在运行期间内波动幅度。 相似文献