Wall heat transfer and dryout governed by disturbance wave frequency in annular two-phase flow

摘要: The dryout of liquid film and the role of disturbance wave frequency is investigated. The Multiphase Flow Visualization and Analysis Laboratory (MFVAL) at UW-Madison has built a facility capable of providing vapor pulses (or density-wave oscillations) with consistent flow rate for long periods of time. Experimental results for heat transfer coefficient (HTC), liquid-film thickness, temporal dry fraction, and dryout statistics under pulsatile conditions are presented. A normalized time-averaged HTC is compared with the fraction of time that the surface is dry. The maximum in HTC associated with local optimal boiling conditions (OBC) occurs when the surface is dry 5% of the time, independent of pulse amplitude and frequency. Liquid-film measurements, dryout statistics, and direct observation indicate that disturbance-wave frequency can be manipulated by density-wave oscillations in the flow field.