Study On The Thermal And Flow Heat Transfer Characteristics Of Fractal Porous Media

Porous media is a heterogeneous mixture widely found in nature,it has a good heat transfer and heat exchange performance,and it is a common fractal multi-scale structure.Traditional research results are mostly fractal theory solutions and related empirical relevance,there are many limitations.The heat transfer process of porous media involves two important processes of heat conduction and flow heat transfer.In this paper,the finite volume method is used to simulate the heat conduction and flow heat transfer process in fractal porous media.The relationship between heat transfer and flow characteristics and structural parameters(scale,porosity and fractal dimension)is studied.Firstly,numerical simulation about porous media is carried out,and the results are compared with the formulas in the literature to provide numerical verification.Then,thermal conductivity of the Sierpinski carpet was studied.The thermal conductivity was 10: 1,100: 1 and 1000: 1,respectively.The results show that the temperature field and heat flux distribution of the fractal are self-similarity,and the equivalent thermal conductivity of the square column is similar to the scale function,and compared with the electro-thermal resistance simulation method.In this paper,the chamfering method is used to discuss the influence of the singular point on the effective thermal conductivity.Then,for the fractal structure with two different fractal dimensions,convection heat transfer process is simulated and analyzed.The results show that the flow streamline of fractal porous media structure is curved,and there is almost no straight line in the whole flow field.In the Reynolds number range,the heat transfer performance of the third type fractal structure 2 is the best.The heat transfer process between fractal structure and uniform structure shows that the fractal structure is more favorable for heat transfer.For fractal porous media,dimensionless Nu number and Re number meet power function growth relationship.Finally,the variation of the flow heat transfer characteristics with the scale is studied,and the correlation between the local and the overall flow heat transfer characteristics of the self-similar structure of the porous medium is discussed.The results show that the flow lines of fractal porous media show the characteristics of bending,and the temperature field distribution has self-similar characteristics.The heat transfer and scale of multi-scale fractal porous media are similar to those of power function.Circular particle group heat transfer performance is better.Finally,fractal porous media structure provide a new kind of method to design a more energy efficient compact heat exchanger.This research explore multi-scale heat transfer mechanism for fractal porous media.