裂隙岩体交叉水流-传热对温度影响的数值分析

Numerical Analysis on Crossed Water Flow and Heat Transfer on the Temperature of Fractured Rocks

裂隙岩体内水流-传热特征是评价高放废物处置库安全运行的重要组成部分。采用3DEC离散元软件建模,着重分析热源温度、裂隙水流速及裂隙开度对裂隙岩体温度的影响。在设定条件下,计算分析表明:(1)由于热传导与水流传热的不规则性,瞬态到稳态,上层岩石形成从下向上为主的传热路径,中、下层岩石形成从左向右为主的传热路径;岩石的温度梯度逐渐减小,裂隙两侧岩石等温线的不连续性逐渐增大;(2)斜裂隙水流与岩石热传导的耦合迟于竖裂隙水流与岩石热传导的耦合,岩石热传导与斜裂隙水流和邻近热源侧的竖裂隙水流对温度分布起控制作用;(3)热源温度越低,裂隙水流速越高,裂隙开度越大,岩石温度越低,系统达到稳态所需要的时间越短;(4)低流速裂隙水的热传导占主导作用,高流速裂隙水的对流传热占主导作用,裂隙交汇处存在局部热对流。

The characteristics of water flow and heat transfer in fractured rocks is an important component for the performance and safety evaluation of high-level radioactive nuclear waste repositories. A 3 D discrete element software was used in model,and the influence of static fracture water,heat source temperature,fracture water velocity and fracture opening on rocks temperature was analyzed. Under the prescribed conditions,the calculations reveal:( 1)due to the irregularities of heat conduction and water flow and heat transfer,from transient to steady state,at transfer paths are mainly from bottom to top in the upper rock layer and from left to right in the middle rock layer and the low rock layer; The temperature gradient of the rock gradually decreases,the discontinuity of the rock isotherm of fracture both sides increases gradually;( 2) the coupling of oblique fracture water flow and thermal conduction is delayed by the coupling of vertical fracture water flow and thermal conduction,in which rock matrix heat conduction and fracture water flow and vertical fracture water flow adjacent to the heat source play dominant roles on the temperature distribution;( 3) the lower the heat source temperature is,the higher the fracture water flow velocity is,the larger the crack open,the lower the rock temperature is,and the system requires shorter time to reach steady state;( 4) the heat conduction of lower velocity fracture water flow is dominant,the convection heat transfer of high velocity fracture water flow is dominant,the junction of fractures exist local heat convection.