Structural stress intensity analysis of hybrid heat exchangers based on thermal hydraulic performance in S-CO2 power cycle

The hybrid heat exchangers (H2Xs) can be used for heat exchange equipment between high-temperature exhaust gas from ships and high-pressure supercritical carbon dioxide (S-CO2) from S-CO2 power cycle. We investigate structural stress characteristics of the H2Xs based on thermal-hydraulic performance. Air and S-CO2 are employed as the working fluids and the Stainless Steel 316 (SS316) as the solid substrate. The thermal-hydraulic performance and structural stress characteristics of the H2Xs is conducted by Fluent and Mechanical, respectively. The results shows the mechanical stress induced by pressure loading and the thermal stress induced by temperature gradient are found to be equally important sources of stress. At the inlet and outlet of the H2Xs, the total stress along all paths is not smooth and continuous, and there will be a significant change due to the change in temperature gradient. The mechanical stress caused by the fluid pressure loss is almost negligible. The change of inlet mass flow rate and temperature mainly affects the stress distribution of the left and right walls on the fin channel. The pressure variation of the diesel engine has little effect on the total stress. Importantly, the total stress intensity of the H2X is mainly affected by the change of S-CO2 fluid pressure.