干热岩人工裂隙三维流动传热的数值模拟研究

Numerical Simulation Study of Three-Dimensional Fluid Flow and Heat Transfer in Artificial Fractures of Hot Dry Rocks

干热岩流动换热模型主要以二维模型假设为主,不能全面反映人工裂隙内的三维流动传热物理过程。利用ANSYS Fluent商业软件建立了单裂隙三维流动换热数值模型,并开展了相关数值模拟计算,分析了不同因素下对于干热岩裂隙内流体温度的影响,获得了裂隙内流体在不同条件下的传热规律。数值模拟结表明:影响干热岩人工裂隙换热的主要因素包括工质注入速度、人工裂隙宽度、人工裂隙长度和流体初始温度。在给定裂隙长度及流入速度的条件下,人工裂隙宽度越小,出口处流出的流体温度越高,流体流经的裂隙长度越长,热突破时间越长。在裂隙宽度、长度相同时,工质流速越小,流体出口处温度越高,流入速度越慢,热突破时间就更长,传递的热量就越多。对于不同的裂隙宽度及流入速度,裂隙长度达到一定程度后,水温才能升高到与基岩一致。

The flow and heat transfer models of hot dry rock are mainly based on the assumption of two-dimensional model,which cannot fully reflect the physical process of three-dimensional flow and heat transfer in artificial fractures.The three-dimensional flow heat transfer numerical model of a single fracture was established by ANSYS Fluent,and the relevant numerical simulation calculation was carried out.The influence of different factors on the fluid temperature in the fracture of hot dry rock was analyzed,and the heat transfer rules of the fluid in the fracture under different conditions were obtained.Numerical simulation results show that the main factors affecting the heat transfer of hot dry rock fractures include:the injection rate of working fluid,fracture width,fracture length and initial fluid temperature.Under the conditions of a given fracture length and inflow velocity,the smaller the width of the artificial fracture,the higher the temperature of the fluid flowing out of the outlet,the longer the length of the fracture which the fluid flows through,and the greater the temperature increase.With the same fracture width and length,the smaller the flow rate,the higher the temperature at the fluid outlet,the slower the flow rate,the longer the heat exchange time,and the more heat is transferred.For different fracture widths and different inflow speeds,after the fracture length reaches a certain level,the water temperature can be increased to be consistent with the bedrock.