Flooding Experiments with Steam and Water in a Large Diameter Vertical Tube

An experimental study on flooding with steam and water in a large diameter vertical tube was conducted. This research has been performed to provide a better prediction of flooding in a pressurized water reactor (PWR) pressurizer surge line to be used in reactor safety codes. Experiments were conducted using a 3-inch (76.2 mm) diameter tube 72 inches (1.83 m) long with subcooled water and super-heated steam at atmospheric pressure as the working fluids. Water flows down the inside walls of the tube as an annulus while the steam flows upward in the middle. The water flow rates ranged from 3.5 to 12 gallons per minute (GPM) (0.00022 to 0.00076 m^3/s) and the water inlet temperature was approximately 70 degrees C. The steam inlet temperature was approximately 110 degrees C. The size of the test section as well as the flow ranges of the working fluids was determined based on a scaling analysis of a PWR pressurizer surge line. Two distinct trends were observed in the data. It was found that for water flow rates below 6 GPM (0.00038 m3/s) the amount of steam required for flooding to occur decreases with an increasing water flow rate. For water flow rates above 6 GPM the amount of steam required for flooding to occur increases with an increasing water flow rate. In addition, axial water temperature data was collected. Axial water temperatures have not been recorded in previous flooding experiments with steam and water. A new correlation for predicting flooding with steam and water was proposed. This correlation was an improvement from previous correlations because it included the amount of steam condensation. Incorporation of steam-water mass exchange promotes a better prediction of behavior in reactor systems. This data for flooding with steam and water in a large diameter vertical tube can lead to a mechanistic model for flooding.