地源热泵岩土导热系数测试影响因素分析

Analysis of Influencing Factors on Soil Thermal Conductivity Test in Ground Source Heat Pump

建立了地源热泵岩土导热系数现场测试系统的三维数值模型,基于所建数值模型分析了测试时间、舍弃初始小时数、钻孔半径、岩土体初始温度、加热器输入功率等因素对岩土导热系数测试结果的影响。研究结果表明:热响应测试时间应大于70h;对于柱热源模型,随着钻孔尺寸的增大,辨识得到的导热系数逐渐减小;岩土初始温度对岩土导热系数辨识结果没有影响,但采用参数估计法作为辨识方法时,岩土初始温度的测试精度对辨识结果有较大影响;对于纯导热模型,加热器输入功率对岩土导热系数辨识结果没有影响。

A three dimensional numerical model of ground source heat pump system was establlshed. The effects of testing time, starting time, borehole radius, initial ground temperature and heat injection rate on identified thermal conductivity of the deep ground soil were analyzed based on the numerical model. The simulation results showed that thermal response test time should be more than 70 h; For cylinder-source model, with the increase of the size of the borehole, the identified thermal conductivity gradually decreased; The initial temperature of ground soil has no effect on the result of thermal conductivity identification, but the testing precision of the initial temperature has larger effects to identification results when the parameter estimation method is adopted; For pure thermal conductivity model, heat injection rate has no effect on thermal conductivity identification results.