With advantages of low system pressure, stable operation and good economic performance, molten salt heat exchanger has recently been widely applied to the field of energy as concentrating solar power, nuclear power engineering, high temperature hydrogen production, and so on.

This study aims to analyze the thermal stress generated in the main components of the U-tube heat exchanger due to the high operating temperature of the molten salt and the large temperature difference between the hot and cold fluids.

Fluid-thermal-solid coupling method was adopted in this study. First of all, the main thermal performance parameters of the heat exchanger were obtained by using computational fluid dynamics (CFD) computation, and compared with experimental results to verify the accuracy of the CFD fluid simulation results. On this basis, the heat transfer process was analyzed in details for the molten salt tube-shell heat exchange under the operating condition, and the flow field and temperature field of the heat exchanger were obtained. Finally, the stress field generated by the coupling of flow field, pressure field and temperature field was calculated by Ansys workbench finite element software, and the stress distribution of the tube sheet connected with the heat exchange tube and shell was emphatically analyzed to find the maximum stress value of the tube sheet and the stress change rule of some paths.

The result shows that the CFD fluid simulation method is feasible with a maximum deviation of 3.07%. The larger stress is found at the connection area between the tube plate and the non-tube, which is located near the inner tube wall on the shell-side with about 2 mm away from the lower surface of tube plate.

Results of this study provides important reference for the actual operation and structural deign of molten salt heat exchanger.