【作者】 李军；

【导师】 王庆超；

【作者基本信息】 哈尔滨工业大学 ， 动力工程， 2013， 硕士

【摘要】 随着超（超）临界机组技术的不断成熟，其作为一种高效的洁净煤技术被应用到越来越多的场合。而超临界锅炉作为超临界机组中至关重要的部分，其水冷壁特性的研究一直是各个国家重点研究的课题。研究锅炉内部水冷壁的传热特性、水动力特性以及阻力特性是提高超临界锅炉运行特性的关键。但是由于超临界压力下的试验对设备要求极高，并且由于试验本身的局限性使得试验研究管内换热存在很大的不足，而数值仿真方法的实现可以在一定程度上弥补试验的缺陷。因此选取合适的数值模拟方法对超临界水的管内换热进行研究意义重大。近几年计算机能力不断提高，数值仿真方法也是逐渐增多。如何根据物理过程选择合适的计算方法吸引了诸多学者的注意力。本文已垂直管内超临界水的对流换热过程为研究对象，就不同的湍流模型对数值模拟的影响、计算结果的可靠性、复杂工况下的数值模拟精度以及管内换热的特性等进行了以下的研究，得出一些结论。本文通过分析实验台设备，根据实验数据建立了超临界水管内换热的三维模型，并确认边界条件。对比不同湍流模型之间的区别，比便了解不同湍流模型可能带来的计算结果和误差。之后根据数值模拟的物理过程选取合适的湍流计模型。同时分析水在超临界压力下的物性变化规律，如比热值，导热系数，动力粘度等，比便设定材料物性。利用已经建立的模型，对三种湍流模型进行网格无关性验证,分析网格精度对计算结果的影响。根据计算结果选取合适的网格进行数值模拟。将使用不同的湍流模型得到的计算结果与实验结果进行对比，分析数值模拟方法的精度和可靠性。同时由于管内存在剧烈的物性变化，会对管内的流动和换热产生影响，因此管内参数变化规律需要进行分析计算。通过对比，选取计算精度较高的湍流模型对复杂工况下的垂直管内水的流动换热进行数值模拟。将计算结果与已有的实验数据进行对比，分析该湍流模型在复杂工况下计算结果。提取轴向和径向的物性参数，通过分析其变化规律研究其对换热的影响，比便管内换热特性的研究；管内换热会存在明显的温度梯度，因此提取轴向和纵向的温度云图，分析温度场的变化规律，寻找其对于管内流动和换热的影响。更多还原

【Abstract】 As one kind of the clean coal technology,the Ultra Supercritical (USC) unitConstruction has being used widely in recent years. The water-wall of thesupercritical coal-fired boilers which is a vital part of the Ultra Supercritical (USC)unit Construction has been paid a lot attention of every contry. Researching the heattransfer characteristics, hydrodynamic characteristics, resistance characteristics ofthe boiler water wall can improve the capability of supercritical coal-fired boiler.However, due to test equipment is extremely demanding in the supercriticalpressure, and the own limitations of the test makes experimental studies filled withgreat insufficient. But the numerical simulation method can offset some defects in acertain extent. So select the appropriate numerical simulation method ofsupercritical water heat transfer is significant.In recent years, as improving of the computer, the numerical simulationmethod is also gradually increasing. According to the physical process, how toselect the appropriate numerical simulation method has attracted the attention ofmany scholars. In this paper, in order to seek out the appropriate numericalsimulation method and the heat transfer characteristics of the supercritical waterheat transfer in vertical pipe, studies about the influencing of different turbulencemodels and the parameter of heat transfer are carried out.Through analyzing the experimental device, a three-dimensional model basedon experimental data is builded with analysising boundary conditions; Then,comparing the differences between different turbulence models is to help select theappropriate turbulent models; The analysis of physical properties of water atsupercritical pressures, such as specific heat, thermal conductivity, dynamicviscosity, etc..With the already established model，the grid-independent using three differentturbulence models is accomplished to reveal the impact on the results and select theappropriate grid. The numerical results applying three different turbulence modelswill be compared with the experimental results, According to the result, numericalsimulation accuracy can be analysised. After the simulation, the physical propertiesinside the tube should be analysised to grasp the heat transfer characteristics.Based on the above calculation and analysis, the turbulence models with ahigher accuracy will be selected for the simulation of complex heat transferconditions. With the calculation results, the applicability of the selected model willbe evaluated.Then, analyzing shaft and radial physical parameters is to understand the affect on the heat transfer.Some study indicates that therie is temperature gradient inside the tube whichimpact the heat transfer. To analyze the effect of temperature gradient, thecharacteristics of temperature field will be analysised throughing extractingtemperature cloud picture.更多还原