Influence of the Main Working Parameters and Geometrical Parameters on the Supercritical CO2 Flow Instability in a Heated Tube

Abstract

Supercritical CO2 (sCO2) flow instability is an issue that must be considered in the reasonable design of sCO2 boiler. Because it can cause equipment vibration and heat transfer deterioration. In this article, a numerical model for the sCO2 flow instability in the single tube was developed. Different from the traditional model, the effects of metal heat storage and axial heat conduction in the tube wall were considered. The influence of main parameters on trans-pseudo-critical number (N TPC) and oscillation period (t 0) was studied, with the tube length (L) from 3 to 11 m and the inner diameter (D in) from 10 to 22 mm. N TPC increases with increasing the inlet pressure (P in), mass flux (G), inclination angle (α), and the inlet local resistance coefficient (K in). N TPC decreases with D in and outlet local resistance coefficient (K out). The effects of the sub-pseudo-critical number (N SUBPC), wall thickness (WT) and L on N TPC are nonlinear. With increasing N SUBPC, WT, L, D in, and K out, t 0 increase. As G, α, and K in increase, t 0 becomes smaller. When N SUBPC is lower than 0.9146, t 0 rises with P in increasing. It is opposite with N SUBPC higher than 0.9146.