The proportion of radiative heat transfer in the total heat transfer increases with the increase in temperature. However, the effect of radiative heat transfer has often been omitted in the heat transfer simulation of molten salt used in complex geometrical systems such as the thermal energy storage (TES) system. In this paper, a 3D helical-coil tube heat exchanger, simplified from a TES system, is established. The temperature difference obtained with and without considering radiative heat transfer is compared. The results show that the effect of radiative heat transfer at high temperatures should be considered. The wall heat transfer coefficient is analyzed, and a heat transfer correlation considering radiative heat transfer is derived. The heat transfer between the molten salt and water is found to enhance when considering the radiative heat transfer. Finally, the effects of different scattering albedo and refractive indices are studied.