Study On Convective Heat Transfer Characteristics Of Supercritical CO2 In Printed Circuit Heat Exchanger Under Ocean Condition

The supercritical carbon dioxide (sCO2) Brayton cycle has a wide application prospect in the field of the waste-heat utilization of the marine gas turbine due to its characteristics of high efficiency, compact, safety and good economy. Inspired by this, the convective heat transfer characteristics of sCO2 in PCHE under static and ocean conditions are studied in this paper. Firstly, a numerical model is established to explore the flow and heat transfer behaviors of sCO2. Then, the heat transfer enhance (HTE) phenomenon of sCO2 flowing in the PCHE channel with airfoil fin under static condition is discussed. Finally, the effects of ocean oscillation on heat transfer performance and frictional pressure drop of sCO2 were investigated under different rolling parameters. Under static state, it can be found that the secondary flow induced by the buoyancy effect obviously increases turbulent dissipation on the upper surface of the channel when mass flow of hot side is lower, which finally results in significant heat transfer difference between the upper and lower walls. However, buoyancy effect has little effect on heat transfer performance at high mass flow rate of hot side. Under rolling condition, the time-average frictional pressure drop of the cold side always increases, but the increment is small with maximum increment of 4.2%. The rolling motion has drag reduction effect on the fluids of the hot side, and the time-average pressure drop at the hot side can be reduced by 20.3% at the high mass flow rate. The time-average heat transfer performance under rolling motion tends to be strengthened, which becomes more significant at low mass flow rate of hot side. Compared with the static state, the time-average heat transfer coefficient can be increased by up to 4.0%. The results have a helpful guiding significance for the design of marine waste heat recovery system.