Heat Storage And Exothermic Properties Of Paraffin Composite Phase Change Materials Containing Gradient Pore Copper Foam

Since the release of the "14th Five-Year Plan",the development of energy storage technology has received widespread attention,among which phase change heat storage technology is not only widely used,but also saves energy and protects the environment.In line with the current energy development requirements of our country.Paraffin wax with its advantages of easy access,low cost and no toxicity,often as a phase change material for phase change heat storage,but its poor thermal conductivity,limited heat storage capacity and other shortcomings seriously limit the development of paraffin in the field of heat storage.In order to solve this problem,foam metal with high thermal conductivity is often combined with paraffin wax to make composite phase change materials to enhance the storage/exothermic properties of paraffin wax.In this paper,we explore the law of using gradient porosity copper to improve the thermal storage performance of foam metal/paraffin wax and its thermal conductivity enhancement effect,consider the parallel and loop placement methods and three different gradient porosity arrangement methods,and analyze and compare the performance influence of copper foam with different porosity distributions on paraffin wax to determine the optimal copper foam arrangement scheme.The research work in this paper mainly includes two parts: firstly,the experimental study on the heat storage and release characteristics of copper foam/paraffin in gradient pore is carried out;secondly,the simulation study on the heat storage and release process of copper foam/paraffin in gradient pore is carried out.The gradient pore copper foam/paraffin composite phase change heat storage test platform was set up,and heat storage and release experiments were carried out.By comparing the temperature change law and temperature uniformity of the measurement points,the influence of adding copper foam on the thermal properties of paraffin was analyzed,so as to obtain the best copper foam layout scheme.On the basis of the experiment,the simulation analysis was carried out to establish the mathematical physical model of storage/heat release of composite materials with gradient copper foam and homogeneous copper foam.The temperature field distribution in the process of storage/heat release was simulated to verify the experimental conclusions and the influence law of gradient porosity on the properties of copper foam/paraffin was obtained.The results are summarized as follows:（1）The thermal storage characteristics of gradient pore copper foam/paraffin wax were experimentally studied.The results showed that adding copper foam composite phase change material could improve the temperature rise rate and temperature uniformity.When copper foams are placed in parallel,the porosity arrangement of 94-96-98 can obviously shorten the melting time,and the heat storage rate is the fastest.When the copper foam type is placed,the temperature rises fastest and the effect is best under the 98-96-94 porosity arrangement.A comprehensive comparison of the temperature rise rate and temperature uniformity of the six groups of composite phase change materials shows that the composite phase change materials with copper foam placed in parallel and pore distribution of94-96-98 have more uniform temperature,and the temperature rise rate increases by 35.9%.The copper foam can melt 15 min in advance,which is the best arrangement of copper foam in heat storage process.（2）The experimental study on the exothermic characteristics of copper foam/paraffin in gradient pore was carried out,and the results showed that adding copper foam could effectively improve the exothermic rate.When copper foams are placed in parallel,the porosity distribution of 94-96-98 can greatly improve the temperature drop rate.When the copper foam is placed back,94-96-98 has the fastest exothermic rate.By comprehensive comparison of the temperature drop rate and temperature uniformity,the copper foam with the porosity of 94-96-98 placed in parallel can increase the temperature drop rate by more than 25%,shorten the solidification time by 30-35 min,and has good temperature uniformity.It is the best arrangement of copper foam in the process of heat release.（3）Conduct simulation study on storage/heat release characteristics of copper foam/paraffin in gradient pore,and obtain temperature distribution of paraffin horizontal section and temperature law of each measuring point in the process of storage and heat release.The results show that the composite phase change material with copper foam parallel distribution and porosity of 94-96-98 can obviously optimize the temperature uniformity,accelerate the heat transfer,and improve the heat storage（release）rate,which is consistent with the experimental results.The maximum deviation between the simulated value and the experimental value is less than 20%,and the simulation results are reliable.