【作者】 宋伟；

【导师】 姚杨；

【作者基本信息】 哈尔滨工业大学 ， 供热、供燃气、通风及空调工程， 2014， 博士

【摘要】 单井循环地下换热系统作为一种新型的地下水源热泵系统热源井，目前共有三种形式，即循环单井、抽灌同井和填砾同井。它们均将抽水管和回水管置于一口井内，在井的下部抽水，上部回水。循环单井是在基岩层中直接开孔，大部分水在井孔之内循环，与井壁发生热量交换；少部分水进入井孔，并进入含水层与其进行原水交换；抽灌同井在井孔内部加设了隔板，将热源井分为三个部分，上部为回水区，中间为隔断区，下部为抽水区；填砾同井的形式和抽灌同井类似，不同之处在于，填砾同井的井孔较井管的直径要大很多，其空隙采用分选性较好的砾石进行回填。本文针对以上三种热源井开展了相关的理论和实验研究工作，主要研究工作及结果如下：设计并搭建了单井循环地下换热系统的物理模拟砂箱实验台，选取了实验测量仪器和数据采集系统，计算了实验误差。结果表明，所搭建实验台的测量误差在可接受的范围之内，能够准确真实地反映物理现象。通过更换不同的预制井来实验模拟三种类型热源井的特性。针对三种不同的热源井，分别进行不同抽回间距、不同初始地温和不同负荷的实验研究。并对循环单井和填砾同井进行了不同排放比例的实验研究。研究表明，增大抽回间距能够显著改善三种热源井的抽水温度、提高换热量。三种热源井中循环单井承担负荷的能力最低，抽回水温度变化最大，热影响范围最小。在取热工况下，排放能够提高循环单井和填砾同井的抽水温度及取热量，小排放比对于提高热源井承担负荷能力的效果较好，随着排放比的增加，这种改善效果减弱。针对不同运行模式下抽灌同井特性进行实验研究，按照三个具有代表性的地区——北京、沈阳和上海采暖期和空调期时间分配来设计实验。实验包括四种工况，即连续取热、连续放热、先夏后冬和先冬后夏。研究表明，抽灌同井在寒冷地区运行过程中，系统在该实验条件下，仅靠自然恢复期内的恢复，地下含水层不能使自身恢复至最初状态。必须采用辅助设备，对地下含水层进行热量补给，保证系统长期可靠的运行。在冷热负荷相当的地区，采用先夏后冬的运行模式，可以提高系统运行的稳定性；在寒冷地区应先进行放热工况，继而进行取热工况，保持热源井的抽水温度处在较高水平。相反，在较暖和地区则应先进行取热工况，保持热源井的抽水温度处在较低水平。建立了多区域耦合CFD仿真模型。通过纳维-斯托克斯方程和伯努利方程对多孔介质中运动方程进行分析推导，得到了多孔介质内的流动模型，并通过实验确定了该流动模型中的经验系数。利用单井循环地下换热系统砂箱实验台测得的实验数据对数值模拟结果进行了对比，验证了仿真模型的准确性。针对三种热源井进行了不同孔隙度、不同初始地温及不同抽水流量三个方面的仿真研究，并分析了三种热源井含水层的流场以及不同流量下的温度场变化情况。研究表明，孔隙度对含水层参与换热较多的抽灌同井和填砾同井影响稍大，对循环单井的影响则较小，但总体上看孔隙度对三种热源井的特性影响不大。抽水流量对单井循环地下换热系统的影响较大，增大抽水流量使得三种热源井的抽水温度变化加大，并能显著提高热源井的热影响范围。初始地温的变化并不影响含水层温度的变化趋势，抽水温度的变化趋势也几乎相同，只是各工况间存在一定温差。但提高初始地温能够显著提高热源井的平均抽水温度和累计取热量，可见初始地温是影响单井循环地下换热系统的关键因素之一。本文为国家自然科学基金“单井循环地下换热系统多流态流动与传热耦合机理研究”(41002085)的部分研究内容。本文的研究工作，为全面的掌握单井循环地下换热系统的运行特性、为该系统的设计及应用提供了重要的理论基础和技术储备。更多还原

【Abstract】 Currently, as a new kind of groundwater heat pump system, single well cycling ground heat exchanger system (SWCGHES) contents three forms of thermal well, e.i. standing column well (SCW), pumping and recharging well (PRW), and pumping and recharging well filled with gravel (PRWFG). Their pumping and injection pipes are placed in a same well, which is pumping water in the low part and recharging water in the top part. The SCW needs to drill hole in the bedrock directly, and then most of the water circulates in the well bore and the heat exchange take place in the well wall, while small part of the water goes out of the borehole and exchanges the heat with aquifer raw water. There are some clapboards in PRW that the thermal well is divided into three parts, i.e. injection zone (in the top part), seals zone (in the middle part), and production zone (in the low part). The PRWFG has similar form with PRW. The difference between them is that the diameter of borehole in PRWFG is longer than the one in PRW. Moreover, the gap of borehole in PRWFG is filled with sorted gravel. In this paper, relative theoretical and experimental researches on these three thermal wells have been carried out. The main research work and results are as follows:A physical simulation experiment table of SWCGHES has been designed and set up, while the experimental testing system and data collecting system have been selected. Additionally, the error of this experiment has been calculated. The results show that the measurement error of the experiment table is within an acceptable range, which can accurately reflect the actual physical phenomena.Different characteristics of three thermal wells have been simulated by replacing the prefabricated inserts. In SWCGHES relative experimental research has been carried out, such as distances between pumping and injection screens (DPIS) variations, initial aquifer temperature variations, and load variations. Additionally, the bleed experiment has been developed in SCW and PRWFG. The results show that with increasing the DPIS, the outlet water temperature and heat transfer quantities of these three thermal wells can be improved significantly. Among these three thermal wells, SCW’s load capacity is the least and temperature variations between inlet and outlet water is the maximum, while its thermal influence scope is the smallest. Moreover, in heating condition the bleed can improve the outlet water temperature and heat absorption quantities of SCW and PRWFG. Smaller bleed rate can improve the heat load capacity of the thermal well significantly. However, with increasing the bleed rate, this kind of improvement effect is weaker.The research on PRW system in different operating modes has been carried out. Time of operating condition has been distributed by heating season and air-conditioning season of three representative regions, e.i. Beijing, Shenyang, and Shanghai, respectively. These experiments include four conditions, e.i. continuous heating condition (CH), continuous cooling condition (CC), summer and winter condition (SW), and winter and summer condition (WS). The results show that in the operation of PRW in cold region the system can not restore in recovery period under the experimental condition. Additionally, the underground aquifer can not make their own return to the original state. Auxiliary equipments must be used for the heat supply of the aquifer, in order to ensure the system in a long-term reliable operation. In the cooling and heating load considerable area, using the SW operation mode can improve the stability of the system. However, in cold area SW operation mode should be used, so that it can keep the outlet water temperature at a higher level. On the contrary, in warm area WS operation mode should be used, while it can maintain the outlet water temperature at a lower level.The multi-zone coupling CFD simulation model has been established. The motion equation in porous media has been analyzed and derived by N-S equation and Bernoulli equation, while the flow model in porous media has been developed. In addition, the experience factors in the derived equation have been determined by experiments. Moreover, the experimental results of SWCGHES are compared with the simulation results, while the accuracy of the simulation model has been validated.Three aspects of simulation study have been carried out that include porosity variations, initial aquifer temperature variations, and outlet water flow rate variations. In these three thermal wells, the aquifer flow field and aquifer temperature field with outlet water flow rate variations have been analyzed. The results show that the effect of porosity on characteristics of these three thermal wells is weaker; however, this effect on PRW and PRWFG is stronger than SCW. The effect of outlet water flow rate on SWCGHES is greater. With the outlet water flow rate increasing, the outlet water temperature of these three thermal wells changes, while the thermal influence scope improves significantly. The initial aquifer temperature variation can not affect the trend of the aquifer temperature variation, while the trend of outlet water temperature is almost the same except some temperature difference among them. However, improving the initial aquifer temperature can increase the mean temperature of outlet water and accumulative heat absorption quantities, which show that the initial aquifer temperature is a key factor in SWCGHES.This paper is a part of national natural science foundation "Study on the Coupling Mechanisms of Multi-Pattern Flow and Heat Transfer in SWCGHES "(41002085). The research in this paper provides a comprehensive grasp of operating characteristics of SWCGHES, while an important theoretical basis and technical reserves are provided for design and application of these systems.更多还原