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《江苏建筑》2018,(5)
针对地源热泵系统中的竖直单U型换热器的传热问题,利用FLUENT软件对其传热特性进行了稳态数值模拟。计算了管内流速,回填物导热系数,支管间距等因素对竖直单U型地埋管换热器换热性能的影响。通过数值模拟发现,管内流速过小时,地埋管换热器会出现严重的热短路现象。对比分析得出管内最佳流速为0.6 m/s~0.8 m/s;进回水支管间距越大,地埋管换热器换热性能越好;回填物的导热系数是影响地埋管换热器换热性能的一个重要因素,其最佳值与管内流速和管间距有关。综合考虑上述3个因素对地埋管换热器换热性能的影响,得出了支管间距为86 mm,管内流速为0.6 m/s~0.8 m/s,回填物导热系数为土壤导热系数的1~2倍时,竖直单U型地埋管的换热性能最好的结论。 相似文献
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地源热泵以其环保特性越来越受到空调界的重视。地下埋管换热器是地源热泵研究的重点和难点之一,不同的地质条件会有不同的换热效果。因此,大连理工大学针对大连地区地质为岩石这一特点建立了地源热泵实验系统。由于单管换热特性足研究地源热泵地下埋管特性的基础,所以实验采用电加热器控制单管的进口水温,使其保持恒定,得出了75m埋深地下换热器夏季2小时内单独运行时在不同进口水温和水流量情况下的换热特性。 相似文献
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《Journal of Building Performance Simulation》2013,6(2):141-155
Common approaches to the simulation of borehole heat exchangers (BHEs) assume heat transfer in circulating fluid and grout to be in a quasi-steady state and ignore fluctuations in fluid temperature due to transport of the fluid around the loop. However, in domestic ground source heat pump (GSHP) systems, the heat pump and circulating pumps switch on and off during a given hour; therefore, the effect of the thermal mass of the circulating fluid and the dynamics of fluid transport through the loop has important implications for system design. This may also be important in commercial systems that are used intermittently. This article presents transient simulation of a domestic GSHP system with a single BHE using a dynamic three-dimensional (3D) numerical BHE model. The results show that delayed response associated with the transit of fluid along the pipe loop is of some significance in moderating swings in temperature during heat pump operation. In addition, when 3D effects are considered, a lower heat transfer rate is predicted during steady operations. These effects could be important when considering heat exchanger design and system control. The results will be used to develop refined two-dimensional models. 相似文献
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介绍了国内外地源热泵换热器技术的理论与试验研究现状,分析了地源热泵换热器传热基本理论,以及现有的各种常用传热设计理论和数值模型,并指出了确定性分析理论与设计方法存在的缺陷。针对地源热泵换热器的复杂实际工况,探讨了地源热泵换热器影响因素的随机特征,提出了地源热泵换热器的可靠度概念和定义、基于可靠性理论的地源热泵换热器研究方法,给出了地源热泵换热器设计步骤。 相似文献
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Development of a numerical model to predict heat exchange rates for a ground-source heat pump system
Ground-source heat pump (GSHP) systems can achieve a higher coefficient of performance than conventional air-source heat pump (ASHP) systems. For the design of a GSHP system, it is necessary to accurately predict the heat extraction and injection rates of the heat exchanger. Many models that combine ground heat conduction and heat exchangers have been proposed to predict heat extraction/injection rates from/into the ground in the research field of heating, ventilation and air-conditioning systems. However, most analysis models are inaccurate in their predictions for long periods because they are based on a thermal conduction model using a cylindrical coordinate model or an equivalent diameter model. In this paper, a numerical model that combines a heat transport model with ground water flow and a heat exchanger model with an exact shape is developed. Furthermore, a method for estimating soil properties based on ground investigations is proposed. Comparison between experimental results and numerical analysis based on the model developed above was conducted under the conditions of an experiment from 2004. The analytical results agreed well with the experimental results. Finally, the proposed model was used to predict the heat exchange rate for an actual office building in Japan. 相似文献
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随着近几年节能减排政策的不断出台,土壤源热泵的应用范围和项目规模不断扩大,但是由于设计、施工及运行中存在的各种原因,一些已经投入使用的土壤源热泵系统工程的节能效果并不如人意。因此,从系统的角度出发,全面分析土壤源热泵系统能效提升中需要把握的几个关键要素,包括:保证低位热源的能量平衡、提高机组自控级别、优化水力输配系统、减少热损失环节、因地制宜按质用能的配置辅助系统、选择适宜的"供冷高温化和供热低温化末端系统装置",以及加强运行监测管理及维护工作。通过这些对这些关键要素的把握,可以改善和提供土壤源热泵的能效情况,具有现实指导价值和意义。 相似文献
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主要针对土壤源热泵系统的垂直地埋管系统进行实际测试,从春夏秋冬4个季节分析单U管和双U管形式与土壤温度的关系,重点分析了土壤源热泵地埋管系统与土壤热平衡问题. 相似文献
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Foundation heat exchangers (FHXs) are an alternative to more costly ground heat exchangers utilized in ground-source heat pump (GSHP) systems serving detached or semi-detached houses. Simulation models of FHX are needed for design and energy calculations. This paper looks at two approaches used for development of simulation models for FHX systems: a simplified analytical model and a detailed numerical model. The analytical model is based on superposition of line sources and sinks. The numerical model is a two-dimensional finite volume model implemented in the HVACSIM+ environment. Both the analytical and numerical models have been validated again experimental results from a test house located in Oak Ridge, Tennessee. Six geographically diverse locations are chosen for a parametric study; results of the two models are compared, and differences between the results are investigated. 相似文献
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