Phase Change Heat Transfer Characteristics Of Phase Change Material Composited With Metal Foam For Battery Thermal Safety Management

In order to achieve the goal of carbon neutralization,we need to promote the new energy,among which the energy storage unit the key points of new energy.As a high energy storage,the thermal safety of battery should pay more attention.As a temperature control system of battery,thermal management system needs to maintain the temperature of battery in the working temperature and reduce the temperature difference between the single energy storage units.This paper starts from the phase change thermal management system,and the goal is to study the three-dimensional heat transfer characteristics of composite phase change materials,to provide reference for the development of phase change thermal management system.In this study,the numerical model of three-dimensional porous media composite phase change materials is constructed,and the melting behavior visualization experiment is carried out at the same time,then the numerical simulation and experimental results are verified.Then,the effects of the three-dimensional square cavity internal heater on the melting performance of the composite phase change materials are studied.The main research contents and conclusions are as follows:1)In the model construction,the real model is abstracted into the three-dimensional unsteady porous medium composite phase change material square cavity internal heater model.In the model equation,enthalpy porosity method is used to describe the phase transformation process of phase change materials,and the phase transition paste area is described by adding source term to momentum equation,and Darcy equation is used to describe the seepage flow of porous media.In the energy equation,the thermal non-equilibrium model is used to separate the energy equation,and the phase change material and porous medium are coupled to calculate each other,and different temperature fields are output independently.At the same time,the melting process of composite phase change materials is tested,the interface and temperature change of the melting process are analyzed.The flow field of the phase change material is analyzed by using the PIV system to explore the key points of the change of heat transfer characteristics.The experimental results are compared with the numerical simulation model to verify the reliability of the numerical model.In the experiment of narrow rectangular cavity,the initial heat transfer efficiency of composite phase change material is significantly higher than that of pure phase change material.Before the melting percentage is about 15%,the composite phase change material is affected by the heat conduction of porous media,which accelerates the process of complete melting.The heat transfer of the composite materials is mainly convection and heat conduction are the auxiliary in the subsequent melting process.The phenomenon shows that the thermal buoyancy is strengthened,and the melting rate of the top part of the cavity is accelerated.2)The phase transformation characteristics of three-dimensional square cavity internal heater model are analyzed.The coupling mechanism of convection heat transfer and heat conduction,structural parameters of porous metal media and heat source parameters on the melting performance of the heat transfer system with internal heat source in the cubic cavity is explored.The results show that the convective heat transfer in the upper part of the porous cavity can be enhanced by increasing Rayleigh number.Although the time for the complete melt remained almost unchanged.For the fixed porosity,the decrease of Darcy number will reduce the melting rate in the melting stage of the medium,while the temperature distribution of the lower west number is controlled by the heat conduction in the porous medium in the later stage,but the influence of Darcy number on the whole melting time can be ignored.For the fixed Darcy,the increase of porosity will reduce the whole melting time.In addition,the size of heater plays an important role in the melting performance of composite phase change materials.3)Based on the internal heater,the influence of different heater and Rayleigh number on the heat transfer characteristics of the composite phase change material in three-dimensional space is analyzed according to the heating model of the battery.The three-dimensional phase transition process,temperature distribution,flow field and average melting percentage will be studied under the influence of Rayleigh number,Darcy number,porosity and heat source size.The results show that with the increase of heat production,the heat conduction intensity is obviously enhanced,and the heat conduction intensity increases significantly reducing the total melting time;while the Rayleigh number enhances the buoyancy effect,thus enhancing the effect of convection heat transfer in the middle of melting and accelerating the melting speed in the middle period.The experimental and numerical simulation of the phase change heat transfer characteristics of porous media composite phase change materials can provide reference for the research and application of the battery thermal management system.