垂直U型埋管换热器准三维热渗耦合模型及其实验验证

为了探讨热渗耦合对土壤源热泵地埋管换热的影响,基于多孔介质传热传质及地下水渗流理论,通过耦合竖直方向一维流体模型与水平面内土壤二维非稳态热渗耦合模型,建立了考虑地下水渗流影响的准三维U型埋管热渗耦合模型。基于模型的数值求解,探讨了土壤热物性及地下水渗流对埋管换热特性的影响。结果显示:土壤导热系数与比热容的增大均有利于加强埋管的换热,且地下水渗流的存在有利于强化地下埋管与周围土壤间的换热能力,提高土壤源热泵系统的运行效率。实验验证表明,所建模型具有一定的预测精度,可为地下埋管换热器传热特性的研究提供理论基础。     

地源热泵系统非平衡冷热负荷运行特性研究

建立地埋管传热模型和系统能耗模型,对非平衡冷热负荷条件下地源热泵系统运行特性进行模拟计算。当建筑空调冷负荷大于热负荷,且供冷时间较长时,地源热泵系统从冬季初始运行,到达夏季时段,地温比夏季初始运行低,更加有利于夏季地源热泵系统节能。地源热泵系统运行7a后,采取夏季和冬季初始运行两种方案的地埋管钻孔壁年平均温度与土壤初始温度相比,分别上升3.10和5.12℃,导致机组耗功率逐年增加,应考虑采用复合式地源热泵系统间歇运行或增设地埋管设置分区运行策略,平衡土壤传热量。     

地源热泵空调机组连续运行过程仿真与经济性分析

对1台额定供冷量为5 kW的地源热泵空调机组进行数学建模,并将其用于地源热泵空调机组夏季连续稳定制冷运行过程的仿真研究,以揭示地下埋管传热特性对地源热泵空调机组运行经济性的影响。研究结果表明,地源热泵空调机组的能耗和COP始终处于变化之中,大致分为急变、过渡和趋稳3个阶段,各个阶段的能耗和COP差别显著,但仍总是优于空气源热泵空调机组。对于该工况下运行的地源热泵空调机组,应以趋稳阶段的能耗和COP作为选型的依据。     

广州地区土壤温度场对U型埋管换热性能的影响

针对广州地下50m以内土壤温度分布来研究广州地区地温的分布特性和变化规律,建立了垂直u型地埋管地下换热区域温度场的三维稳态和瞬态传热模型.同时就该系统在冬季和夏季运行分析了不同工况下埋管区域土壤温度场的分布情况以及进一步确定了热泵机组连续和间歇运行对地埋管换热性能、埋管区地温恢复状况的影响.最后,通过对某别墅工程的动态负荷计算,选用ASHRAE推荐的地埋管地源热泵设计模拟软件GLHEPRO 3.0进行30a运行模拟,分析得到了地下埋管区域土壤热平衡对埋管换热性能的影响程度,从而为华南地区推广使用地埋管地源热泵系统的长期高效运行提供理论参考.     

土壤源热泵U型埋管换热器传热的非稳态数值模拟

本文基于能量平衡方程,建立了土壤源热泵U型埋管换热器周围土壤的非稳态传热模型,用所建立的传热模型对土壤源热泵冬季取热过程进行了动态模拟.研究了不同物性土壤温度及U型埋管出口流体温度的变化规律,分析了土壤物性对换热器换热性能的影响,采用间歇运行方式提高了换热器换热能力.通过建立数学模型得出的结果,可供设计参考.     

垂直埋管热湿传递线源模型的建立及其计算条件

现有的土壤传热模型忽略了水分迁移对传热的影响,根据质量与能量守恒原理,在原有的垂直埋管土壤源热泵一维线源模型上发展了传热传湿数学模型,并对模型中土壤的各参数进行了分析,为下一步的数值模拟计算以及进一步研究土壤含水率对传热影响奠定基础。     

竖埋螺旋管地热换热器理论模型及实验研究

对竖埋螺旋埋管地热换热器建立了传热模型，分析了流量、土壤传热系数对热输出的影响，并计算了等效传热系数、竖埋螺旋埋管换热器对土壤温度场的影响情况。在理论计算的基础上，对一竖埋螺旋管地源热泵系统进行了实验研究，对比分析了理论计算值和实验测试值，并分析了热泵系统的性能。     

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。     

U型管桩埋换热器稳态传热模拟研究

采用能量平衡的方法建立了土壤层内U型管桩埋换热器稳态传热模型，并以天津市一地源热泵实际工程为背景，模拟计算了管脚热影响因子、土壤导热系数等对U型管桩埋换热器的传热特性的影响。     

冬季工况下埋管换热器换热特性实验与模拟对比分析

利用土壤源热泵实验系统,进行不同埋管间距下冬季连续运行实验。采用FLUENT模拟软件建立竖直U型埋管的等效传热模型,对不同实验工况进行了数值模拟,将获得的实验数据与模拟结果进行对比分析。通过分析,得到了不同埋管间距对土壤源热泵系统性能的影响,土壤温度场变化对地埋管换热器换热性能的影响规律。     

提高地能利用的强化传热试验研究

以太阳辐射积聚大量能量和冷热良性循环蓄集巨大能量的地下是一个庞大的可再生能源库，也是一项可充分利用的自然能量资源。该文介绍了在地源热泵系统中开展的地下100m和200m竖直井闭式循环传热的研究工作，提出利用地下螺旋芯管束新方法，加强旋流流动，提高地下换热能力。试验表明，在放热和吸热过程中，传热均得到显著提高。所提出的可控制间歇过程，将充分发挥换热井的换热能力，实现最少的井数布置，保证良好的地源热泵机组运行工况。     

Evaluation of estimation method of ground properties for the ground source heat pump system

Technology directed at geothermal energy, one of our renewable energy sources, to heat and air-condition buildings has become very attractive in recent years following the significant developments in ground-source heat pump (GSHP) systems. In general, although the energy efficiency of GSHP systems is far superior to conventional air-source heat pump (ASHP) systems, GSHP system is still expensive. Therefore, GSHP system employs the foundation pile of buildings as heat exchanger is introduced in order to reduce the initial cost. When designing a GSHP system (especially in case of the energy pile system), it is necessary to accurately predict the heat extraction and injection rates of the heat exchanger. The thermal and hydraulic properties of the ground are very important to accurately predict heat transfer between the ground heat exchanger and the ground. In particular, those are the most important design parameters because energy pile system is installed only a few tens of meters deep. In this paper, an estimation method is suggested in order to determine the thermal and hydraulic properties of the ground for design the heat exchanger of energy pile system base on geotechnical investigation for the design the building's foundations. The use of results from generally applied geotechnical site investigation methods to estimate ground thermal and hydraulic properties was evaluated.     

A study on the performance of a geothermal heat exchanger under coupled heat conduction and groundwater advection

Being environmental friendly and with the potential of energy-efficiency, more and more ground-source heat pump (GSHP) systems are being widely used. However, the influence of groundwater advection on the performance of the geothermal heat exchanger (GHE) in a GSHP is not still clearly known. In this paper, the configuration of a vertical dual-function GHE used in an integrated soil cold storage and ground-source heat pump (ISCS&GSHP) system, which charged cold energy to soil at night and produced chilled water in daytime in summer, and hot water for heating in winter, is firstly presented. This is then followed by a report on a mathematical model for the GHE considering the impact of the coupled heat conduction and groundwater advection on the heat transfer between the GHE and its surrounding soil. The GHE model developed was then integrated into a previously developed simulation program for an ISCS&GSHP system, and the operating performances of the GHE in an ISCS&GSHP system having a vertical dual-function GHE have been studied by simulation and reported. These simulation results, firstly seen in open literature, are much helpful to the design of a GHE buried in soil and widely used in GSHP systems or ISCS&GSHP systems.     

Theoretical study on the performance of an integrated ground-source heat pump system in a whole year

Being environmental friendly and with the potential of energy-efficiency, ground-source heat pump (GSHP) systems are widely used. However, in southern China, there exists large difference between cooling load in summer and heating load in winter. Thus the increase of soil temperature gradually year-by-year will decrease the COP of the GSHP system. In this paper, the configuration of a vertical dual-function geothermal heat exchanger (GHE) used in an integrated soil cold storage and ground-source heat pump (ISCS&GSHP) system, which charged cold energy to the soil at night and produced chilled water at daytime in summer, and supplied hot water for heating in winter, is presented. This is then followed by reporting the development of the mathematical model for the GHE considering the impact of the coupled heat conduction and groundwater advection on the heat transfer between the GHE and its surrounding soil. The GHE model developed was then integrated with a water-source heat pump and a building energy simulation program together for a whole ISCS&GSHP system. Then the operation performance of the ISCS&GSHP system used for a demonstration building is studied. These simulation results indicated the system transferred 71.505% of the original power consumption at daytime to that at nighttime for the demonstration building. And the net energy exchange in the soil after one-year operation was only 2.28% of the total cold energy charged. Thus we can see the feasibility of the ISCS&GSHP system technically.     

湿土壤含湿特性对传热影响研究

针对于地源热泵地能换热系统在具有热源条件下土壤热湿迁移现象,进行了初步分析和实验,并对模拟计算应用可行性进行了认证。土壤含水静态传热实验,目的在于探讨土壤含湿程度对传热能力的影响,以及地下含水程度对换热区域换热性能的影响。研究土壤不同含水率情况下的传热性能,从而推断含水率在工程中的影响程度。为进一步研究地源热泵应用中关于土壤含水的传热问题奠定基础。     

土壤源热泵埋地换热器的简便计算

土壤源热泵是利用土壤作为吸热和排热源的一种高效、节能、环保的热泵技术,近年来得到了快速的发展。本文介绍了一种简化的土壤与埋地换热器的传热数学模型,并利用Foxpro编制了简便、快速的计算程序。     

北方地区岩土导热系数及换热量的测试研究

岩土导热系数是地源热泵地埋管换热器的重要设计参数;测井单位深度换热量是地埋管换热器系统的设计依据。掌握工程区域岩土的热物性及换热性能,是保证地源热泵系统高效、稳定运行的关键。文章建立了现场测试岩土导热系数及换热量的方法,并结合沈阳浑南高新技术产业开发区某地源热泵工程,测试分析了岩土导热系数和测井单位深度换热量。结果表明,该区域的岩土具有较好的导热能力,适合采用地埋管地源热泵系统;在特殊地理条件下设计地源热泵系统方案前,应对拟建区域的地质条件进行全面勘探,以优选工程区域,为岩土热响应测试结果的可靠性提供保障。     

Experimental study of heat transfer of buried finned pipe for ground source heat pump applications

Ground heat exchangers have vital importance for ground source heat pump applications. Various configurations tried to improve heat transfer in the soil. A new kind of aluminium finned pipe buried in the soil for this aim. In order to compare effectiveness of the Al finned pipe over the traditional PPRC pipe an experimental study carried out. The experimental GSHP system was installed at Y?ld?z Technical University Davupasa Campus on 800 m² surface area with no special surface cover. Temperature data were collected using thermocouples buried in soil horizontally and vertically at various distances from the pipe center and at the inlet and the outlet of the ground heat exchanger. Experimental results were compared with results from analytical study. To compare effectiveness of the Al finned pipe and PPRC pipe a new parameter defined as transferred amount of heat per unit mass of working fluid per unit time for this aim. It is found that Al finned pipe has higher heat transfer values than the traditional PPRC pipe.     

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。     

地源热泵换热器可靠性设计方法研究

介绍地源热泵换热器传热模型和设计方法的研究现状,分析地源热泵换热器传热影响因素的随机特征,提出地源热泵换热器的可靠度分析方法,讨论采暖热能指标及设计值的变异性。结合工程实例提出基于可靠性理论的地源热泵换热器设计与分析方法。