Phase change heat storage technology has received extensive attention because it can ease the energy utilization problem of uneven energy distribution in time and space. In this study, a multichannel flat tube phase change thermal storage unit that adopts a new multichannel flat tube as the core heat transfer element, air as the heat transfer fluid, and lauric acid as the phase change material is designed and fabricated. Experimental results show the charging/discharging temperature and power variation curve of the device at different air volumes and inlet temperatures. The optimum heat transfer fluid flow was obtained through experiments. Compared with 1D and 2D numerical models proposed by other researchers, we presented and established a 3D numerical model to verify the experimental results. The simulation results exhibit good agreement with the experimental results and show that the natural convection of phase change material in the melting process plays an important role in accelerating melting.