Study On The Ledinegg Instability In Boiling Channel

The Ledinegg instability has been a cause for the burnout of boiling channel, which spurs the studies on Ledinegg instability in boiling channel.A simple and practical Ledinegg stability criterion for parallel n channels is developed by using the matrix analysis method based on the characteristic equation. The criterion shows that there is at most one channel whose slope of the pressure drop-flow rate curve is less than or equal to zero while the other channels' slopes of the pressure drop-flow rate curves should be greater than zero in order to make sure that parallel n channels is stable when the slope of pump pressure head-flow rate curve is less than zero. It is found that decreasing the slope of pump pressure head-flow rate curve, and introducing inlet restrictor for each channel can enhance the stability of parallel channelsThe parametric trends of Ledinegg instability for single channel is analyzed, which shows the stability range for single channel decreases with the heat flux and inlet temperature increasing, and increases with the hydraulic diameter and outlet pressure. The effect of non-uniform heat flux on the Ledinegg instability of subcooled boiling in parallel channels when the slope of pump pressure head-flow rate curve is equal to zero is analyzed, which shows the potential stability range of total mass flux for parallel two channels increases with the heat flux evenness when the heat flux evenness is large, keeping nearly a constant value when the heat flux evenness is small, and the potential stability range of total mass flux for parallel three channels reaches the maximum when the heat fluxes for all channels are identical.Based on the momentum difference equation, the Ledinegg instability in boiling channel is simulated, and the effect of initial perturbation on the flow excursion for each equilibrium operational point is studied. The results show the system will return to the initial operational point regardless of whether the initial perturbation value is positive or negative if the initial operational point is stable, and the system will spend more time returning to the initial operational point with the absolute value of initial perturbation increasing. When the initial operational point is unstable, the flow rate will increase(decrease) gradually to a new value corresponding to a new equilibrium operational point if the initial perturbation value is positive(negative), and the system will spend more time reaching the new equilibrium operational point with the absolute value of initial perturbation decreasing.