土壤源热泵型U埋管换热器传热研究

【作者】 闫晓娜；

【导师】 张国强；

【作者基本信息】 南京理工大学 ， 供热、供燃气、通风及空调工程， 2006， 硕士

【摘要】 土壤源热泵系统利用地下土壤作为冷(热)源，具有节能和环保的特点。采用U型垂直埋管换热器的土壤源热泵以其占地面积小、适用范围广、性能稳定、换热效率高等优势得到了越来越广泛的关注和应用。 本文介绍了土壤的物性，结合相关文献给出原始地温计算式。针对垂直U型埋管换热器建立瞬态传热模型，采用控制容积法对方程进行离散，对换热器周围土壤温度场和管内流体温度进行数值模拟，模拟结果与实验数据吻合的较好。结果表明：靠近管井壁面的区域径向温度梯度大，远离管井壁面的区域土壤温度变化不明显。随着土壤源热泵在制冷工况下连续运行，埋管出口介质温度和管井壁面温度逐渐升高。热泵刚开始运行的一段时间，管井壁面温度升高的很快，随着运行时间的增加，温度变化减小，直至达到某一稳定温度值，系统处于稳定状态。稳定后的换热器传热半径可用于确定两管井的最小间距。进一步分析了单位长度管井换热量对换热性能的影响，单位长度管井换热量越大，可减小埋管长度和管井数，但埋管出口介质温度相应也越高，热泵制冷性能降低。因此应根据土壤特性，选择合适的单位长度管井换热量。本文在利用温度频率法分析建筑冷热负荷的基础上给出了确定垂直U型埋管地下换热器长度的方法。此外，对混合式土壤源热泵也作了初步探讨，通过实例分析出混合式土壤源热泵节能效果显著。以上分析为系统设计提供一定参考价值。更多还原

【Abstract】 The Ground-Source Heat Pump system makes full use of soil as cold or heat source and boasts the features of protecting the environment and saving energy. GSHP with the adoption of the vertical U-tube heat exchanger has become increasingly popular because of such outstanding advantages as fewer area requirement, fewer limits, more steady and effective performance etc.This paper introduces edaphic characteristics and presents the equations to determine the undisturbed ground temperature based on relevant literature. A transient heat transfer model for the simulation of a single vertical U-tube heat exchanger is built and the controlled equation is dispersed in terms of Finite Volume Method. The temperatures of soil and fluid in U-tube are simulated and simulation results and experiment datum are consistent. The results indicates near the wall of tube well the radial temperature grad is great and far from the wall the grad is little. Along with GSHP running at refrigerate condition the temperatures of the out medium and the wall gradually rise. At the beginning the temperatures of wall of U-tube and soil rise quickly and along with the Heat Pump running the temperatures change tardily until the temperatures are steady. The system will be at steady state. Then, the least space between the well and the adjacent well can be fixed. Analysis of the quantity of heat exchange of unit length tube well having effects on exchanger capability indicates the tube length and the number of well can be reduced if the quantity of heat exchange is increased. But the out medium temperature will be higher and the Heat Pump refrigerate capacity is lower. Appropriate quantity of heat exchange of unit length tube well should be chose according to edaphic characteristics. This paper provides a method to determine the length of vertical U-tube exchanger based on BIN method calculating building load. What’s more, this paper researches the mixed Ground Source Heat Pump and proves the mixed system’s energy saving is evident by analyzing an example. Analysis above is essential conditions to design the Heat Pump system.更多还原