In order to investigate the most effective means of heat transfer enhancement，four different kinds of heat storage units—the bare tube with pure paraffin，the finned tube with pure paraffin，the bare tube with paraffin/expanded graphite composite material and the finned tube with paraffin/expanded graphite compound material were studied numerically and the performance was compared.The heat transfer performance of the fourth unit was the best one for all the units

while that of the second unit and the third unit were similar and were both better than the first unit.When the mass flow rate of heat transfer fluid（HTF）at the inlet was 0.02 m·s-1，the heat retrieval duration for the fourth unit was only half of that in the first unit.Moreover，the temperature of the HTF at the outlet was nearly 5 K higher than that in the first unit.The heat transfer enhancement became more evident with increasing the mass flow rate and decreasing the temperature of the HTF at the inlet.