Numerical and experimental studies are conducted on convective heat transfer performance of carbon dioxide(S-CO_2) flowing in a heated vertical helically coiled tube under supercritical pressure. The influence of flow characteristics and structural characteristics such as heat flux q

mass flow rate G

pitch P

tube inner diameter d

and spiral radius R on heat transfer are discussed

and the sensitivity of each structural parameter is studied quantitatively. A closed-loop S-CO_2 test platform was built to conduct experimental research on the convective heat transfer performance of S-CO_2 in the helically coiled tube

and the accuracy of the numerical simulation is verified based on the experimental data. Finally

the heat transfer correlation of S-CO_2 is fitted. The research has laid foundation for the thermal design method of S-CO_2 spiral-wound heat exchanger

and has certain engineering application value for the application and promotion of the spiral-wound S-CO_2 heat exchangers in nuclear power and solar thermal power generations.