【作者】 黄光勤；

【导师】 卢军；

【作者基本信息】 重庆大学 ， 供热、供燃气、通风及空调工程， 2014， 博士

【摘要】 土壤源热泵利用地下岩土作为热泵机组的低品位热源（汇），具有高效节能、环境友好的优点，但是由于传统垂直U型土壤源热泵系统钻孔费用较高，特别是重庆、成都等岩石地质结构，初投资高，经济性差，在技术推广过程中阻力较大。对于螺旋型地埋管换热器而言，由于其能够依托建筑基础，可较大程度节约钻孔费用，减少了系统初投资，有利于技术推广应用。但是由于螺旋型地埋管换热器几何结构较为复杂，且具有埋深浅、桩径大的特点，其传热机理与换热特性有异于传统垂直U型地埋管，传统的地埋管传热模型不能正确描述其传热现象；此外，土壤表面环境参数（空气温度、太阳辐射等）的动态变化对埋深较浅的螺旋型地埋管的传热过程具有较大的影响，但是目前描述螺旋型地埋管传热过程的物理模型未深入考虑上述影响，故在上述工程实际问题及研究现状的基础上，本文对螺旋型地埋管换热器的传热模型及换热特性进行了研究。首先，对螺旋型地埋管换热器的导热模型进行了研究，建立了区别回填料与岩土热物性差异的螺旋型地埋管换热器实心圆柱热源一维导热数值解模型及线圈热源二维导热数值解模型，并与忽略热物性差异的导热解析解模型做了定量对比，分析了一维及二维模型的温度空间分布特征及温度时间变化特征。其次，在研究导热模型的基础上，提出了螺旋型地埋管在柱坐标系统下的单元体离散方法，并在此基础上建立了动态环境作用下螺旋型地埋管换热器的三维数值传热模型，该模型了考虑了回填料与岩土热物性差异及动态土壤边界条件对传热的影响，采用visual studio程序开发平台中C#程序设计语言，编制了螺旋型地埋管换热器设计与动态模拟软件；利用提出的螺旋型地埋管三维数值传热模型，模拟分析了地埋管设计参数、运行工况、螺旋形式、覆土深度、初始温度分布对传热特性的影响，提出了螺旋型地埋管沿流动方向上的4个典型换热阶段：进口换热换热阶段、回填区域热短路换热阶段、小温差换热阶段及出口换热阶段，分析了设计参数与运行工况等因素对4个换热阶段换热特性的影响。然后，考虑管群作用对螺旋型地埋管换热效果的影响，将传热区域分为单桩传热区域与管群传热区域，采用导热解析解模型与三维数值解模型分别描述管群传热区域与单桩传热区域传热过程，提出“动态土壤径向边界热流”的概念，将单桩传热区域与管群传热区域进行耦合，从而建立了考虑管群作用下适合系统长期模拟的螺旋型地埋管换热系统的传热模型；另外，考虑机组负荷率、冷凝器水温及水量、蒸发器水温及水量等5个因素，建立了螺杆热泵机组变工况能效模型；在螺旋型地埋管换热系统的传热模型及机组能效模型的基础上，模拟分析了重庆气候条件下，无辅助散热措施情况下地埋管系统的典型月响应特性、过渡季节温度恢复特性及典型年动态响应特性；然后通过调整夏季负荷，模拟了考虑辅助散热措施情况下的地埋管系统响应特性。最后，以贵阳城乡规划展览馆螺旋型地埋管热泵系统为案例项目，进行了实验性测试，分析了系统原始工况的运行特性，并提出了优化运行模式，在次日对优化运行模式进行了测试，发现冷热源系统能效提高了26.1%。另外，基于本文提出的三维传热模型与原始工况测试数据，确定得出测试项目埋管区域的岩土热物性参数，利用得出的热物性参数，预测了螺旋型地埋管换热器在优化运行工况条件下的出水温度，预测结果表明：本文提出的螺旋型地埋管三维传热模型具有较高的精确度，能够可靠的预测地埋管水温变化情况。更多还原

【Abstract】 Ground source heat pump utilizes the soil as the low grade heat source/sink, whichhas the advantages of energy saving and environmental friendly. However, thetraditional U-type ground source heat pump has high initial cost duo to the expensivedrilling cost such as Chongqing and Chengdu, and the technology promotion is difficult.For ground heat exchanger with spiral coils, because it would be installed on thebuilding foundation and reduce the drilling cost greatly, the initial cost of the systemwould be decreased, which is conducive to the technology promotion in the practicalengineering. However, duo to the complex geometric construction of helix ground heatexchanger and the characteristics of shallow buried depth and bigger pile diameter, theheat transfer process is difference from traditional U-type ground heat exchanger andthe heat transfer model of the traditional wouldn’t present the heat transfer phenomenonaccurately. Besides, the dynamic change of ground surface boundary conditions (airtemperature and solar radiation) would affect the heat transfer because of the shallowburied depth. The existed heat transfer models don’t consider the above influencefactors. Therefore, based on the above practical engineering problems and researchstatus, the heat transfer model and characteristics of ground heat exchanger with spiralcoils under effects of dynamic environment are studied.Firstly, the conduction models of the helix ground heat exchanger are studied, andthe one-dimensional conduction numerical model based on solid cylinder heat sourcemodel and the two-dimensional numerical model based on ring-coil source model arepresented, which have considered the thermal property difference between the soil andthe grout. A comparison between numerical model and analytical solution model hasbeen carried out quantificationally and the spatial distribution and time variation of theground temperature for one-dimensional and two-dimensional model are discussed.Secondly, a new discretization method for helix ground heat exchangerincylindrical coordinatesystem is proposedbased onthe investigation ofheat transfermodels.And a dynamic three-dimensional numerical heat transfer model of helix groundheat exchanger is presented, which considers the impacts of thermal propertydifferences between the pile grout and the surrounding ground as well as the dynamicground boundary conditions on heat transfer. A dynamic couplingsimulationdesignsoftwarefor helix ground heat exchanger is developed using c#programming language on visual studio application development platform with theproposed three-dimensional numerical heat transfer model, the impacts of designparameters of underground heat-exchangers, operating conditions, forms of spiral,covering depth and initial temperature distribution on the heat transfer performance aresimulated and analyzed, which is supposed to providesupports for engineering design.Besides, four heat exchange stages of helix ground heat exchanger are proposed and theinfluences of design parameters and operating conditions on the four stages are studied.Then, considering the multi-pile effect on heat exchange of helix ground exchanger,the heat transfer area is divided into one pile region and multi-pile region. The heattransfer processes for the two regions are described respectively by analytical solutionmodel and numerical solutionmodel and the concept of dynamic ground radial boundaryheat flux is proposed and used to connect the one pile heat transfer region and multi-pileregion, which makes the model applicable to long-term simulations under the multi-pileeffect. Also, an energy efficiency model for heat pump units under variable conditions isestablished considering5factors, including:load rateof unit, condenser watertemperature and flow rate, evaporator water temperature and flow rate. Based on thethree-dimensional numerical heat transfer model with spiral coils and theenergyefficiency model for heat pump units, ground heat-exchange systems with and withoutshelter are simulated under the climate condition of Chongqing and without auxiliaryheat dissipation, and the response characteristics of typical months, temperaturerecovery features of transition seasonand dynamic response characteristics of typicalyear are analyzed. In addition, the system response characteristics is also studied undercondition of auxiliary heat dissipation by adjusting the summer cooling load.Finally, the helix ground heat exchanger heat pump system of Guiyang UrbanPlanning Exhibition Hall is taken as a case study and anexperimental test was carried.The operating characteristic of original working condition is analyzed and an optimizingoperation model is proposed and tested in the next day. The test results find that thesystem efficiency of the optimizing operation model increases by26.1%. Besides, basedon the developed three numerical heat transfer model and the test data obtained byoriginal operating condition, the soil thermal property was determined used to predictthe water temperature of the helix ground heat exchange system in the test period. The results of prediction indicate that the proposed three numerical heat transfer model ofhelix ground exchanger has high accuracy characteristic and it would reliably predictthe change of water temperature of the helix ground exchanger.更多还原