EXTENSION OF FLOODING DATABASE FOR LARGE DIAMETER TUBE AT VARIABLE PRESSURE INCLUDING HYSTERESIS EFFECTS

Abstract

An experimental investigation into flooding phenomena was conducted to acquire data using steam/water and air/water fluid pairs at varying conditions within a large diameter vertical tube with annular flow. Experiments were performed to expand the database previously collected and verify correlations developed. Additionally, experimentation was conducted to determine hysteresis effects that may occur during flooding. Experiments were completed in a previously established vertical test section. Flooding tests were conducted by forming an annular liquid film within the test section then injecting gas into the bottom of the test section until reversal of the annular film. Tests were performed at various gas inlet flow rates with water inlet flow rates ranging from 5 to 8 gallons per minute, and pressure varying from atmospheric pressure to 45 psig. Data collected extends the range data beyond previous studies at the Nuclear Heat Transfer Systems laboratory. Data were collected in 0.5 GPM increments for the liquid mass flow rate range, filling out the data set previously collected. The additional data increases the reliability of the flooding database and flooding curves. Integration of the new data set with previous data enhances understanding of the effects of pressure, gas-liquid combination, and condensation effects of flooding phenomena. Post-processing of data produced flooding curves to compare data sets. Integration of flooding data showed that when data is plotted as dimensionless Kutateladze parameters showing that fluid-pair data overlay onto one another and a slight dependence on pressure of the system is present for steam/water data. Hysteresis data was post-processed, and hysteresis curves produced, both gasliquid systems exhibited hysteresis effects, namely as the gas flow rate was incrementally decreased, flooding occurred at a Kutateladze gas inlet parameter below that which is required to initiate flooding. The data suggests that higher carryover mass fraction can be sustained when the gas flow rate is being lowered from a flow rate beyond that needed to achieve the onset of flooding, effects were more dramatic at higher water inlet flow rates and pressures. Further, air/water mixtures showed more hysteresis than steam/water mixtures.