THe heat transfer characteristics of a latent heat storage system of ternary carbonate eutectic mixture have been studied in a shell-tube type heat exchanger. The eutectic exhibits a distinct phase change temperature during the thermal cycles. In the heat storage stage, the thermocline in the axial direction is pronounced. In the heat release stage, the heat transfer rate increases with the Biot number but the quality of thermal energy decreases. The thermal conductivity of the eutectic and the heat transfer coefficient have been determined. The temperature distribution and freezing front velocity in the heat recovery stage have been well represented by the approximate solutions.