In order to improve the heat storage efficiency of the constant pitch spiral coil heat storage device,a cylindrical gradual pitch coil type phase change heat storage device with paraffin wax as the phase change material was proposed.The spiral coil heat storage device has a long tube length and the uneven temperature distribution during the heat storage process,causing the phase change time to increase.Therefore,an optimization algorithm for gradual pitch was proposed,and a set of optimal gradual pitch was selected through Gaussian fitting and FLUENT software simulation.The heat storage processes of gradient and constant pitch heat storage devices at different inlet temperatures and flow rates were simulated,and the heat storage characteristics of the two devices were studied through FLUENT simulation and experiment.The results show that compared with the constant pitch phase change heat storage device,the gradual pitch phase change heat storage device can better couple the heat storage characteristics of PCM,which can shorten the heat storage time to a certain extent.