Cooling Heat Transfer of Supercritical CO2 in Diverging and Converging Microtubes

Abstract The motivation of this research was to solve the problem of heat transfer deterioration of supercritical CO2 in tubes. The cooling heat transfer of supercritical CO2 in diverging and converging microtubes was numerically studied. Under the conditions proposed, the heat transfer coefficient of the tube wall is relatively uniform. When the heat transfer coefficient becomes most uniform, the diameter change rate of the diverging microtube is greater than that of the converging microtube. Both the Richardson number and the relative difference of the heat transfer coefficient increase with increasing tube diameter, indicating that the buoyancy effect is the reason for different heat transfer coefficients in different flow directions.