In order to research the heat transfer problem of organic phase change materials melting in the square cavity heat storage unit, liquid fraction and mean Nusselt number of composite phase change materials under different filling rates during melting are analyzed. To solve the problem of heat accumulation at the top of the square cavity unit, the layered model is constructed to simulate the melting process of the composite phase change materials in different models The results show that when the contents of graphene nanosheets arc 1%, 3% and 5%, the complete melting times of the nanoparticle-enhanced phase change material arc 32. 1, 20. 0 and 17. 5 min, respectively, which are 70. 47%, 81. 62% and 83. 92% shorter than those of pure paraffin. When the square cavity is equally divided at the top and bottom, the melting time is reduced by 11. 88% compared to the unlayered one. When the upper and lower parts of the square cavity arc filled with 1% and 5% volume fraction of the composite phase change materials respectively, the melting time of the composite phase change model with an overall filling of 3% is reduced by 25. 83% compared to that when it is not divided into layers. From the simulation results, it can be concluded that the addition of graphene nanosheets to paraffin wax can lead to a large degree of improvement in its thermal conductivity, as well as a smaller degree of viscosity growth and a smaller effect on natural convection. When considered together, it can be found that the addition of graphene nanosheets to paraffin can strengthen its heat transfer performance; the layered model can shorten the melting time of the phase change materials, and a suitable filling scheme can further accelerate the melting process of the rectangular cavity. © 2023 Xi'an Jiaotong University. All rights reserved.
