Heat transfer and thermal performance of two-stage molten salt steam generation system

Heat transfer and thermal performance of two-stage molten salt steam generation system were experimentally reported and analyzed. The experimental system consisted of primary U-shaped steam generator and secondary shell and tube superheater, and its overall heat transfer coefficient, steam generation rate and thermal efficiency had been studied in detail. According to experimental results, molten salt heat convection, boiling heat transfer and heat loss played important roles in heat transfer of steam generation system. The absorbed heat flux and overall heat transfer coefficient of primary U-shaped steam generator were remarkably higher than those of secondary shell and tube superheater, and the thermal performance of superheater was significantly affected by steam flow rate from steam generator. When inlet molten salt temperature/flow rate rose, overall heat transfer coefficient and steam generation rate first increased for convection enhancement of molten salt with high velocity or low viscosity, and then decreased for the reduction of boiling heat transfer coefficient at high temperature. As inlet molten salt temperature/flow rate rose, thermal efficiency increased firstly and dropped later due to the combination of absorbed heat flow and heat loss. In addition, the optimal inlet molten salt temperature with maximum absorbed heat flow was a little higher than that with maximum thermal efficiency. (C) 2017 Elsevier Ltd. All rights reserved.