【作者】 陈砥；

【导师】 李素芬；

【作者基本信息】 大连理工大学 ， 热能工程， 2009， 硕士

【摘要】 土壤源热泵是一种节能、环保、高效利用可再生资源的“绿色”空调新技术,在我国建筑空调系统中发挥着越来越重要的作用。垂直U型管换热器由于其占地面积少、可用范围广、恒温效果好、换热效率高、维护费用低等优势,目前已成为应用最广泛的一种埋管方式。垂直U型管换热器主要分为两种:单U型管换热器和双U型管换热器。目前,对于单U型管换热器的研究较多,大多数的土壤源热泵采用的都是单U型管换热器。近年来,双U型管换热器以其钻井利用率高和换热性能好等优点开始被广泛应用。本文首先针对热渗耦合作用下的单U型管换热器,建立了换热器周围热渗耦合土壤及管内流体的物理数学模型。将土壤考虑为均匀的、各向同性的多孔介质,地下水为三维渗流,土壤沿深度方向分层,考虑其热物性沿深度方向变化。采用Fluent软件对埋深50m埋管换热器夏季连续运行20天后的土壤温度场进行数值模拟。本文的创新之处在于:①考虑了土壤沿深度方向的热物性变化,使模型更接近实际情况;②将地下水的渗流视为三维渗流,考虑土壤沿深度方向的传热。这与以前的研究者将土壤视为单一的土壤类型,以及只考虑土壤的二维渗流,忽略土壤沿深度方向传热的数学模型相比都有了改进。本文研究了不同回填材料、入口温度及入口流速对土壤温度场及埋地换热器换热性能的影响。针对不同运行参数下的换热进行模拟。研究结果对土壤源热泵运行参数的经济性选择具有一定的参考价值。本文采用同样的方法建立了双U型管换热器的三维非稳态传热模型,研究不同回填材料、入口温度及入口流速对土壤温度场及埋地换热器换热性能的影响。并从换热器出口水温,换热器换热率等方面比较了双U型管换热器与单U型管换热器运行特性的不同。结果表明,双管换热器的性能要优于单管换热器,可以提高钻井的利用率。更多还原

【Abstract】 Ground Source Heat Pump(GSHP) system increasingly applied in architectural air-condition as these systems can make significant contributions to reduction in electrical energy usage,using renewable resource efficiency,and have been recognized as an environmental-friendly alternative to conventional unitary system.Vertical U-tube heat exchanger have been widely used because of many notable advantages it has,such as fewer area requirement,extensive application,running steadily,high performance,lower cost on system maintenance etc.Vertical heat exchanger is mainly divided into single U-tube heat exchanger and double U-tube heat exchanger.At present,single U-tube heat exchanger is widely used and research on heat exchanger is mainly about single U-tube.Recently, application of double U-tube heat exchanger rises for its better heat transfer performance and higher utilization efficiency of borehole.In this paper,the model of fluid in the U-tube and underground soil around single U-tube heat exchanger under coupled thermal conduction and groundwater seepage were set up.Soil was considered as the even,isotropy and saturated porous medium,and the seepage of groundwater had three-dimensional characteristic.Soil was layered along the depth direction, and the thermal property change was taken into consideration.The Fluent software was used to carry out the numerical simulation of soil temperature field of ground heat exchanger with burial depth 50m after 20 days continuous operation on summer conditions.The creative points of this paper are:①the thermal property change along the depth direction was taken into consideration,which make the model more close to the reality;②the seepage of groundwater had three-dimensional characteristic,and heat transfer in soil along the depth direction was considered.Compared with the model used by early researchers,in which the soil was considered as single type or the seepage had two-dimensional characteristic,it’s an essential progress.In this paper,the soil temperature field and heat transfer performance with different inlet fluid temperatures,backsoil and inlet velocities were studied.The operation with different parameters was studied,that has reference value for chosen of operating parameters of ground-source heat pump.The model of fluid in the U-tube and underground soil around double U-tube heat exchanger was constructed in the same way,and the soil temperature field and heat transfer performance with different inlet fluid temperatures,backsoil and inlet velocities were studied. The performance of single U-tube heat exchanger and double U-tube heat exchanger was compared based on temperature difference between inlet and outlet and heat transfer rate.It can be concluded that the double U-tube heat exchanger offered a better performance than single U-tube heat exchanger.更多还原