Efficiency improvement of the indirect supercritical CO2 turbine system for fast reactors by applying micro-channel intermediate heat exchanger

Two types of intermediate heat exchanger, shell-and-tube type and microchannel heat exchanger (MCHE) type, have been designed for a Na-cooled fast reactor with an indirect supercritical CO2 turbine. MCHE is a kind of Printed Circuit Heat Exchanger (PCHE) and it uses sinusoidal offset fins that were developed at the Tokyo Institute of Technology (TIT). Its heat transfer and pressure drop correlations were developed based on CFD analysis results, we recommend: Nu equals 0.186*Re0.61*Pr0.4 and friction factor f equals 0.11*Re-0.17. Design results indicate that the value of pressure drop was less than 1% and was very low for the MCHE compared with 8.65% for the shell-and-tube type. In the MCHE, the flow cross-sectional area is large and the CO2 velocity is small. Therefore, it has similar heat transfer area to that of the shell-and-tube type. Nevertheless, the heat transfer volume is only 8% of that for the shell and tube type due to denser arrangement. Consequently, results revealed that cycle thermal efficiency of 45% was achieved in the fast reactor power plant with an MCHE intermediate heat exchanger installed