Improvement of the heat transfer of the cold side is one of the approaches to enhance the performance of TEG systems.As a new type of heat transfer media,nanofluids can enhance the heat transfer performance of working liquid significantly.Based on a three-dimensional and steady-state numerical model,the heat transfer and thermoelectric conversion properties of TEG systems were studied.Graphene anoplatelet aqueous nanofluids were used as the coolants for the cold side of the TEG system to improve the heat transfer capacity of the cold side.The results showed that the heat absorbed by the hot side,voltage,output power,and conversion efficiency of the TEG system were increased greatly by the nanofluid coolants.The output power and the conversion efficiency using 0.1-wt％ graphene nanoplatelet aqueous nanofluid as the coolant are enhanced by 26.39％ and 14.74％,respectively.