Study On Heat Transfer Characteristics Of Foam Metal Reinforced Phase Change Materials

The high energy density and its good handling of latent heat have become the focus of heat storage research.However,it is also difficult to apply the traditional phase change materials(PCM)due to its low thermal conductivity.Porous media(PM)has a special grid structure.As a special porous media,Foam Metal plays an important role in assisting PCM in improving thermal conductivity.However,the internal structure of foam metals is complex and there is no certain regularity.All physical parameters will affect the phase transformation melting / solidification process of PCM.After making PCM composite foam metal,the mutual capacitance and relativity between the two will affect the phase transformation ability and thermal conductivity of the composite.Firstly,the foam metal /PCM composite phase change material was prepared by vacuum injection method.Foam metal and PCM were foam copper and paraffin respectively,and the thermal properties of pure paraffin and foam copper / paraffin composites were characterized,and the changes of various parameters(thermal conductivity,specific heat capacity and thermal diffusivity)were recorded.The phase change melting experiment of foam copper / paraffin composites was designed,and the relevant experimental platform was built.The temperature of pure phase change material and composite material was measured by thermocouple and infrared thermal imager.The difference between the two phases was determined,and the best melting interval was determined.The influence of the metal skeleton of foam copper on the internal temperature field was also considered.Under the same porosity(95%),changing the parameters of foam copper(pore density: 10,20 and 30PPI),repeated experiments were carried out to obtain the characteristics and rules of temperature changing with time.Finally,the error analysis of the above experiments is carried out to ensure the accuracy of the experiment.In numerical simulation,the temperature,velocity,density and pressure field of foam copper/ paraffin composites under the melting model(Melting Model)are analyzed.According to the size of the sample used in the experiment,the corresponding physical and mathematical models are established,and the grid is divided,and then the independence is verified.According to the material and chemical assets of PM and PCM,the beginning facters and boundary conditions are fitted to make the equation converge;the imitation results are contract with the experimental results.According to the test,the melting spot temperature and latent heat value of phase conveyance were gained.The thermal conductivity of froth copper/paraffin compound material is obviously higher than that of pure paraffin wax,and the distinct heat volume decreases.The addition of copper foam shortens the melting time of paraffin wax.The metallic properties and skeleton structure of foam copper strengthen heat conduction,but also inhibit the influence of natural convection.With the decrease of pore density,the thermal conductivity of foam copper with high porosity will increase.Repeated experiments,with a reasonable error of 5%,prove the precise of the experiment.The analogy results are in perfect treaty with the experimental data.The spreading of temperature region is allied to that of density region.The total area begins to thaw from the upper,and the foot is having heatstroke unevenly;two eddy flow are taken shape by the natural convection;because of the effect of copper foam skeleton,natural convection and gravity settlement,the pressure field inside the composite material is unbalanced,resulting in the increase of pressure and cross star distribution.