The Pore-scale Numerical Study Of Flow And Heat Transfer In Foam Metal At High Velocity

Foam metal belongs to ultra light porous medium.It has honeycomb structure,high thermal conductivity and large cavity volume.It can optimize the structure designing according to the demand,and has become an excellent candidate material for radiator and compact heat exchanger.It has a good application prospect in the field of aerospace.However,its internal complex pore structure brings many inconveniences to explore the internal flow,and the principle of heat transfer enhancement in porous media at high speed is not perfect.With the development of computer,computational fluid dynamics（CFD）has revolutionized the ideas and methods of fluid mechanics experiment;Applying numerical simulation to foam metal,the simulation experiment based on topological structure is more convenient and efficient.In this paper,the convection heat transfer behavior in foam metal is numerically studied by means of CFD software by Fluent,and the heat transfer law of porous metals under high velocity is obtained through second data collected in the flow field.Based on simplifying the structure of the tetrakaidecahedron cell,we construct the foam metal topological structure.The heat transfer analysis of the structure is carried out by using Fluent.The temperature field,pressure field,velocity field,convection heat transfer coefficient and heat transfer factor in the computational domain at high velocity are obtained according to the variation of foam metal structure parameters and velocity.A foam metal structure with an overall porosity of 0.934 and 0.97,then the 10-40 PPI pore density was constructed.The two key parameters of pressure drop and convection heat transfer coefficient were selected as reference values.The accuracy and reliability of the modeling structure were determined by comparing with the experimental and simulated data.Then,the temperature field,pressure field and velocity field of air flowing through the foam metal are analyzed and compared.The distribution of the basic physical field in the computational domain of foam metal and the flow state near the foam metal skeleton structure are obtained,and the influence of the microstructure of the foam metal on heat transfer enhancement is obtained.Subsequently,the pressure drop resistance and convective heat transfer performance of foam metal with different pore density（10-40PPI）at high flow rate are studied.The influence of pore density on the pressure drop resistance,the comprehensive convection heat transfer coefficient,the comprehensive evaluation factor of heat transfer and the interfacial heat transfer coefficient on the surface of foam metal at 0-100m/s velocity were obtained.The results show that the pressure drop of high pore density foam metal is higher than that of metal foam with smaller pore density,and the higher the pore density of foam metal is,the greater convective heat transfer coefficient will be.The convection heat transfer coefficient increases with the increase of flow velocity,but the difference does not rise at the increase of flow velocity.The conclusion is drawn that pore density and velocity of foam metal can affect heat transfer coefficient and pressure drop,but the pressure drop in the basin is more affected by the velocity.For the foam metal with the same pore density,the higher the flow velocity is,the lower the comprehensive evaluation factor of heat transfer will be.The foam metal with a pore density of 40 PPI has the best comprehensive heat transfer performance in the four selected pore densities.At the same time,the fitting formula is given to predict the trend of the change of the heat transfer coefficient between the metal pressure drop and the phase boundary.In order to ascertain the influence of porosity in the foam metal on the above parameters,a porous metal structure with porosity of 0.934 was established and compared.It is found that high porosity has better convective heat transfer performance and porosity when the pore density is the same.The ε= 0.97,foam metal with a pore density of 30 PPI can overcome the flow resistance and have the best heat transfer capability under the 6 conditions.