高温围岩封闭空气夹层隔热的理论与数值分析

随着矿井开采深度的增加以及深埋隧道的发展,高地温地下空间热害问题日益突出,研究如何控制围岩散热在其热害治理中具有重要意义。结合空气夹层在建筑围护结构中保温隔热的作用,提出应用封闭空气夹层控制围岩散热量的隔热方法。利用FLUNET建模分析了巷道为不同截面形状时相应封闭空气夹层结构内的自然对流换热特性,拟合了不同形状巷道的空气夹层内平均自然对流强化系数的计算式K_ave=f(Ra,2δ₂/d₃)。得到以下结论:(1)不同形状巷道的自然对流强化情况不同,差异产生的原因是空气夹层顶部对流换热强度不同;(2)空气夹层隔热方法可有效降低巷道壁面的总放热量;(3)空气层厚度对岩壁散热量影响不显著,但巷道底部宽度对总放热量有明显影响,最佳空气层厚度为8 cm左右。

Theoretical and Numerical Analysis of Enclosure Air Layer Thermal Insulation in High Temperature Tunnel

With the increase of mining depth and the developing of deep tunnel, the problem of thermal damage in high temperature underground space is increasingly serious. It is of great significance to study how to control the heat dissipation of surrounding rock in heat damage control. Combined with the effect of air layers on heat insulation in building envelope, an enclosure air layer heat insulation method was proposed to control the heat transfer from the surrounding rock. The natural convection heat transfer characteristics in the enclosure air layers with different tunnel shapes were studied by using the model established by the FLUNET software. The formula K_ave=f(Ra,2δ₂/d₃)for calculating the mean natural convection enhancement coefficient in the enclosure air layers of different shape tunnels was fitted. The results include the following items: (1)The enhancement of natural convection heat transfer differs with different tunnel shapes, and the reason for the difference is that the convective heat transfer intensity at the top of the air layer is varying. (2)The air layer insulation can effectively reduce the total heat dissipation of the roadway wall. (3)The thickness of the air layer has no significant effect on the heat dissipation of the surrounding rock, but the width of the bottom of the roadway has an obvious effect on the total heat dissipation of the surrounding rock and the best thickness is about 8 cm.