Study On Flow Resistance Of Porous Metal Foam

Porous media refers to a porous space composed of a porous solid skeleton filled with single-phase or multiphase media.With the development of human science and technology gradually,porous metal foam refers to a new type of material that it has foam pores,extremely high porosity,certain strength and stiffness,small density,good sound insulation performance,and it can absorb electromagnetic waves.Porous metal foam can be seen everywhere such as in our daily life and industrial production field.Aluminum foam is suitable for automobile shock absorber and electronic mechanical device,nickel foam is used for filter,atomizer,catalysts and heat exchanger,copper foam is used for the preparation of battery cathode materials,catalyst carrier,and electromagnetic shielding materials and magnesium foam can be used to replace human bones as the ideal bionic materials.Flow problem has always been a hot and difficult in the field of porous metal foam.So the research on the flow of porous metal foam is of great significance to the research and development of biological,construction,chemical industry,aerospace materials and so on.However,due to its complex internal structure and cross-bending pore channels,it is very difficult for the fluid to flow through the metal foam,and the flow resistance of the fluid through the metal foam has been widely concerned by scholars from all walks of life.This paper mainly researches on porous metal foam flow resistance problem.(1)First of all,reading lots of literature in English and Chinese,extracting experimental data related with porous metal foam and traditional porous media and analyzing them.(2)Secondly,selecting the traditional flow resistance correlation formula of porous media,the common flow resistance correlation formula of porous metal foam and Ergun's equation,making them dimensionless,and substituting the experimental data into them for exploring their applicability.It can be found that these flow resistance formulas have different applicable ranges for porous metal foam.(3)Then,when constructing the new model and the flow resistance formula,it is necessary to choose the classical Ergun's equation to compare with it,and the coefficients of Ergun's equation are determined according to different conditions.Therefore,modifying the coefficient of Ergun's equation.The corrected coefficients of the first term and the second term are 624 and 2.93 respectively.The modified Ergun's equation is applicable to the foamed metal with porosity between 0.799 and 0.88,particle diameter between 0.6mm and 2.47 mm.The medium of fluid is air.The maximum error is 40.29%,the minimum error is 2.01% and the average error is 16.74%.(4)Up to now,there is no fixed model and correlation formula for calculating the flow resistance of porous metal foam.Therefore,it is necessary to construct a new and widely applicable model and flow resistance correlation formula.In this paper,the five-ball fork row pore throat model is constructed.The total flow resistance can be treated as capillary caused by the pipe flow resistance,aperture changes caused by the local resistance,overlapping and converging caused by the flow around resistance.According to this model,we can derive correlation formula.According to the value of unit length,we can make the corresponding improvement.The correlation is related to porosity,pore throat ratio,density,viscosity,particle diameter,tortuosity and flow coefficient.It is suitable for the foamed metal with porosity between 0.799 and 0.88,particle diameter between 0.6mm and 2.47 mm.The medium of fluid is air.The maximum error is 30.33%,the minimum error is 0.08% and the average error is 12.34%.(5)Finally,using the experimental data of porous metal foam to verify the derived correlation and making error analysis.It is found that the correlation deduced in this paper is in good agreement with the experimental data.This shows the five-ball fork row pore throat model and the correlation has certain applicability and rationality.In this paper,the five-ball fork row pore throat model's construction is based on the classical and widely used structure model,it can be used in the research of porous metal foam flow resistance and it is referred to by the porous media flow resistance problem.It is of great significance to the development of the flow resistance theory in the future,but this model can be extended and generalized to all types of porous metal foam also need to explore and research constantly and do a lot of work to correct and perfect.