| Porous media are ubiquitous in nature and widely used in various fields of industry,agriculture and national economic production.It is difficult to avoid the existence of natural and artificial cracks in porous media.Cracks have an important influence on heat transfer in porous media,and rational use of cracks is beneficial to strengthen heat transfer and weaken heat transfer.In recent years,scholars at home and abroad have done a lot of research on the seepage characteristics of porous media containing fractures and obtained a lot of research results.The research results on natural convection and heat transfer in porous media with fractures need to be further expanded.In this paper,a reasonable range of fracture inclination Angle is abstracted through the morphology of porous media fractures in nature,and a physical model is established.Through experiments,numerical calculations and theoretical analysis,the natural convection and heat transfer characteristics of porous media containing fractures under the action of different fracture angles were studied.The main research contents are as follows:(1)The flow and heat transfer characteristics of fluid in porous media were studied by experimental method.Through analyzing and studying the experimental results of 10 kinds of fracture dip Angle porous media models,it is found that:the fracture Angle?=0~?or?=90~?porous media takes the longest time to reach the steady state,about 720min,and the heat transfer rate is the slowest.The corresponding time required for the porous media to reach the steady state was the shortest,about 420min.For porous media with fractures distributed in the direction of vertical gravity,the heat transfer rate is higher when the cracks rotate counterclockwise than when the cracks rotate clockwise.For porous media with fractures distributed along the direction of gravity,the temperature gradient on the left side of the fracture is greater than that on the right side,and high-temperature fluid accumulates on the left side of the fracture.(2)by the numerical method,the vertical direction of gravity,along the gravity direction distribution inside the porous medium fluid flow and heat transfer characteristics of cracks,the numerical results found that the open cracks to appear in porous medium cavity body"preferential flow,vertical flow field of the role of gravity direction distribution of cracks,the first secondary vortex,and then in a vortex,cracks along the direction of gravity,on the other hand;Due to the influence of secondary vortexes and gravity,heat transfer to the low temperature side is hindered,but the local heat transfer rate is accelerated and the average temperature increases,which is reflected in that the smaller the Nuavg,the larger the Tavg in the cavity.The fluid flow intensity distributed along the gravity direction under the action of cracks is greater than that of the fluid flow intensity distributed along the vertical gravity direction under the action of cracks.?=75~?,the temperature difference between the left and right cavity of the crack was the largest,and the heat resistance of the crack was the strongest.Ra=10~7 helps to distribute heat transfer of cracks along the direction of gravity.To sum up,under the action of temperature field,the distribution of flow field in porous media is changed due to different fracture angles,which leads to the redistribution of temperature field.It provides certain theoretical guidance for practical engineering applications(such as oil,gas,water resources development,coal mine heat damage prevention and control,and greenhouse gas storage,etc.),and contributes to national economic construction and the development and utilization of new energy.This paper contains 48 pictures,7 tables and 85references. |
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