The thermal conductivity of phase change materials (PCM) within latent heat storage devices is small and the rate of heat storage is low

which is problematic to the widespread utilization of latent heat storage devices. Consequently

the phase change process of a two-stage series cascade heat storage device based on composite phase change materials was numerically studied. By comparing and analyzing the results of different PCM with different thermal properties

the heat storage characteristics of the device were obtained. The results show that there is an optimal thermal diffusivity

so that the PCM with fixed melting point achieves "a uniform constant-velocity phase change". At the same time

increasing the thermal diffusivity of the PCM can effectively reduce the heating surface temperature

but the decline in heating surface temperature was minimized with a continuous increase in thermal diffusivity. By analyzing the Stefan number

the optimal parameters of the device were obtained. Finally

the correctness of the rule was verified by an experimental study when the Stefan number was 2.88.