基于数值实验的干热岩裂隙对流换热系数研究

Study on convective heat transfer coefficient of fracture in hot dry rock based on numerical experiment

裂隙换热系数是干热岩地热资源评价、开发及模拟表征中的重要参数,通常需要通过试验测试得到。本文通过数值实验与控制变量法,丰富干热岩裂隙内的对流换热实验数据,利用现有裂隙换热系数公式计算裂隙换热系数,分析不同公式得到的换热系数随实验参数的变化规律,探讨裂隙换热系数公式的适用性。结果表明:各公式得到的换热系数随岩石试样外壁面温度的升高而增大,换热系数与流量之间的关系因不同公式而异,换热系数与裂隙开度之间呈正相关或负相关关系受流量大小的控制。部分理论公式在流量足够大时出现负值,另一部分理论公式的数值稳定性、适用性较好。

Fracture heat transfer coefficient(HTC),which is usually obtained by test,is an important parameter in evaluation,development and simulation of geothermal resources in hot dry rock.In this paper,numerical experiment and control variable method are carried out in order to enrich the experimental data of convective heat transfer in fractures of hot dry rock.Firstly,the heat transfer coefficient of fractures is calculated by using the existing heat transfer coefficient formula of fractures,then,the variation law of heat transfer coefficient obtained by different formulas with experimental parameters is analyzed,and finally,the applicability of heat transfer coefficient formula of fractures is discussed.The research results show that the heat transfer coefficient obtained by each formula increases with the increase of the temperature of the outer wall surface of rock samples and the relation of heat transfer coefficient and flow rate varies with different formulas.It demonstrates that the positive or negative correlation between the heat transfer coefficient and the fracture opening is controlled by the flow rate.Some of the theoretical formulas have negative values when the flow is large enough,and the other ones have good numerical stability and applicability.