裂隙通道内流固换热系数解析解及敏感性分析

ANALYTICAL SOLUTION AND SENSITIVITYANALYSIS OF FLUID-SOLID HEAT TRANSFER COEFFICIENT IN FRACTURE CHANNEL

以增强型地热系统中岩体裂隙通道内换热问题为核心,应用局部非热平衡法,针对圆柱岩体裂隙内流动换热理论模型,依据岩体截面二维导热方程推导出单裂隙流固换热系数解析解。通过将可测参数带入计算方程中,得出在不同工况条件下的换热系数,并与文献中将岩体半圆截面等效为矩形一维导热模型所计算数据进行对比。结果表明在相同裂隙开度条件下,当流速较低时其结果与文献得出的结果吻合较好,但随着流速的增大误差逐渐增大。利用敏感性分析法,在外壁温变化条件下,分析裂隙开度与流速对换热系数的影响,表明流速的影响略大于裂隙开度。

The fluid and solid heat transfer of enhanced geothermal system in fracture channel was especially researched using the local thermal non-equilibrium method. For the heat transfer theoretical model of current flowing in fracture of cylinder rock, the analytical solution of fluid- solid heat transfer coefficient for single fracture was derived according to the 2D heat conduction equation on rock cross section. All the measurable parameters were substituted into calculation equation and the heat transfer coefficients for the different conditions were calculated, which were compared with calculation data in the literature in which the rock with semicircular cross section was equivalent to a rectangular heat transfer model. The results show that the present result in low flow speed coincides well with the data in the reference for the same fracture aperture, but the error between present work and reference becomes greater with the increasing flow speed. Using the sensitivity analysis method, at the different outer surface temperatures, the effect of the flow speed and the fracture aperture on the heat transfer coefficient is discussed, the results indicate that the heat transfer coefficient is more sensitive to flow speed than to the fracture aperture.