Abstract
The flow instability has been extensively investigated in the past as it can lead to a premature critical heat flux (CHF) at the heat flux level much lower than that for stable conditions, but the relationship between the flow instability and CHF is still unclear. In view of this, an analysis model of CHF under flow instability in forced circulation has been proposed in this paper, which adopts the classical instability theory analysis of the pressure difference resulting from a small disturbance perpendicular to the liquid-vapor interface, and the flow instability characterized by periodic mass flow fluctuation is hypothesized to exert upon the small disturbance, which results in the change of interfacial curvature. When the heat flux closes to the CHF, the intense vapor production will lift the liquid-vapor interface away from the heater surface, preventing the supply of liquid from contacting the heater surface. Soon after, the CHF occurs. The results of the model indicate that the amplitude and period of the flow instability significantly influence the CHF, which is in the form of q_<CHF>〜q_0[1-0.43(ΔG)/(G_0)^<0.427>(τ/T)^<0.263>], i.e. the CHF under flow oscillation decreases with increasing amplitude and period of flow instability, and the model also can satisfactorily predict the experimental data available in literature.
