Numerical study on flow instability of parallel helical tubes under convective heating condition

The present study numerically investigated the flow instability in parallel helical tubes under various conditions using a one-dimension code SGTH-1D. The effects of non-uniform heat flux, curvature ratio and inlet throttling configuration are investigated. The results show that the convective heating condition can significantly improve the system stability compared with uniform heating. The single-phase length and pressure drop are both more significant under convective heating. However, the effect of the curvature ratio is limited. The maximum difference in critical exit quality between different systems is merely 0.028. Two inlet throttling configurations are investigated, that is, throttling at the inlet of each tube and at the inlet manifold. The system stability is enhanced when the throttling is imposed at the inlet of each tube. This study can be used as a valuable reference for the design and operation of the H-OTSG.