地源热泵地下垂直埋管换热器的换热研究

发布时间：2018-04-17 06:29

本文选题：地源热泵 + 换热热阻　；参考：《湖南大学》2015年硕士论文

【摘要】：现如今,能源短缺已成为社会的首要问题之一,地源热泵以其优越的节能环保的特性得到了越来越多的应用。因此,对于地源热泵的性能研究也是人们首要关心的问题之一。而地下换热器是地源热泵换热的重要部件,直接影响到地源热泵整个系统的运行性能。由此,本文主要从三个不同的角度对地源热泵地下换热器的换热性能进行研究。换热热阻直接影响到地源热泵地下换热器的换热性能,因此本文利用地源热泵单U地埋管二维换热模型,以钻孔内的换热热阻为目标函数,以回填材料导热系数、两埋管间距及管内水流速等参数为优化变量,利用遗传算法,对各参数同时变化时进行了目标函数优化,并分析了各参数对热阻性能影响。研究得出在钻孔孔径和埋管管径组合一定的情况下,当回填材料导热系数、两埋管间距及管内流体流速均为最大值时,钻孔内换热热阻达到最优。用单U、双U地埋管地源热泵准三维换热模型,以能效系数及嗾效率为评价指标,通过Matlab自编程序,计算出流体出口温度,并利用流体进口温度、流体质量流量、埋管深度等分析了这些影响参数对单U及双U埋管换热器的换热性能的影响。研究得出双U地埋管换热器的能效系数及嗾效率均高于单U地埋管换热器。利用FLUENT数值模拟软件建立起一个二维有限体积的模型,瞬态模拟了单U埋管换热器管壁不同时刻的温度响应。单U埋管换热器的两个支管的温度响应由地埋侧的传热平衡方程进行求得,并通过FLUENT中的UDF编写程序得以实现。研究得出当使用下降管与上升管换热量所占的比例分别为60%与40%时来分析地下换热时更接近实际情况。不同的连续运行时间对地温的恢复有着不同的影响,连续运行的时间越长,地温恢复到原始温度所需要的时间也就越长。
[Abstract]:Nowadays, energy shortage has become one of the most important problems in society. Ground source heat pump (GSHP) has been applied more and more because of its superior energy saving and environmental protection characteristics.Therefore, the performance of ground source heat pump is also one of the most important concerns.The ground heat exchanger is an important part of the ground source heat pump, which directly affects the operation performance of the whole system of the ground source heat pump.Therefore, this paper mainly studies the heat transfer performance of ground source heat exchanger from three different angles.Heat transfer resistance directly affects the heat transfer performance of ground source heat pump (GSHP) ground heat exchanger. In this paper, the heat transfer coefficient of backfill material is taken as the objective function and the heat transfer resistance in borehole is taken as the objective function by using the two-dimensional heat transfer model of ground source heat pump (GSHP) single U buried tube.The parameters such as the distance between two buried pipes and the velocity of water in the pipe are optimized by genetic algorithm. The objective function is optimized when each parameter changes simultaneously and the influence of each parameter on the thermal resistance performance is analyzed.The results show that the heat transfer resistance of the borehole is optimal when the heat conductivity of the backfill material, the distance between the two buried pipes and the flow velocity in the pipe are the maximum when the combination of the bore hole aperture and the buried pipe diameter is certain.The quasi three dimensional heat transfer model of single U and double U ground source heat pump is used. Taking the energy efficiency coefficient and baiting efficiency as the evaluation index, the outlet temperature of the fluid is calculated by Matlab program, and the inlet temperature of the fluid and the mass flow rate of the fluid are used.The influence of these parameters on the heat transfer performance of single U and double U buried tube heat exchangers was analyzed.The energy efficiency coefficient and efficiency of double U buried tube heat exchanger are higher than that of single U ground tube heat exchanger.A two-dimensional finite volume model was established by using FLUENT software, and the temperature response of the tube wall of a single U-tube heat exchanger at different times was transient simulated.The temperature response of two branch tubes in a single U tube heat exchanger is obtained from the heat transfer equilibrium equation of the buried side and realized by the UDF program in FLUENT.The results show that when the proportion of heat transfer between descending tube and rising tube is 60% and 40% respectively, the underground heat transfer is closer to the actual situation.Different continuous operation time has different influence on the ground temperature recovery. The longer the continuous operation time, the longer it takes to recover the ground temperature to the original temperature.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU83

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