Convection heat transfer of CO2 at supercritical pressures in a vertical mini tube with a diameter of 0.948 mm was investigated experimentally and numerically. The local heat transfer coefficients, bulk fluid temperatures and wall temperatures were measured and presented. The effects of inlet fluid temperature, fluid pressure, mass flow rate, heat flux and wall thickness on the convection heat transfer in the mini tube were investigated. The experimental results were compared with calculated results using well-known correlations and numerical simulations. The results showed that the variable thermophysical properties of supercritical CO2 significantly influenced the convection heat transfer in the vertical mini tube and that for the studied conditions the influence of the wall thickness on the convection heat transfer in the mini tube was not great. For bulk fluid temperatures higher than the pseudo-critical temperature, the simulation results and the correlation results for the convection heat transfer coefficients in the mini tube corresponded well to the experimentally measured results.

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