To study the effect of inlet temperature and flow step changes on dynamic performance of supercritical carbon dioxide(S-CO_2)/lead-bismuth coupled heat exchanger

a segmental model was established for numerical simulations. Based on the simulation results

a transfer function model was developed and validated to quantitatively assess the effect of inlet step disturbances on the cold-side outlet temperature. The results show that

under inlet temperature step disturbances

the heat exchanger responds quickly

but the temperature field changes with a smaller amplitude. The time constant for the temperature step change at the hot-side inlet is 22.1 s. When the cold-side inlet temperature decreases by 50 K

the temperature at the midpoint of the heat exchanger only drops from 795.23 K to 793.17 K. Under flow step disturbances

the heat exchanger responds with a delay

but the temperature field changes with a larger amplitude. The time constant for the cold-side inlet flow step change is 30.08 s. When the cold-side flow increases to 0.002 kg/s

the temperature at the midpoint of the heat exchanger drops from 795.23 K to 779.08 K. The transfer function established in this study shows good agreement with the results from the segmental model. The findings provide useful insights for the operational strategy of intermediate heat exchangers in the S-CO2 power cycle and the lead-bismuth fast reactor coupling system.