STEAM BUBBLE FORMATION AT A SUBMERGED ORIFICE IN QUIESCENT WATER

Abstract

The formation of steam bubbles at a submerged orifice in quiescent water was studied theoretically and experimentally. The experiments were performed for liquid temperature from 80 to 98-degrees-C, for liquid height above the orifice from 2.5 to 10 cm, for orifice diameter of 1.48 mm and for constant pressure difference of 245 Pa between the vapor pressure in the vapor chamber and the hydrostatic pressure of the orifice. The flow rate of steam entering through the orifice, the detachment time of the bubble, and the bubble size at detachment were increased as the temperature of the water in the liquid column was raised. Sixty-two per cent of the steam was condensed at a liquid temperature of 80-degrees-C and 11% at 98-degrees-C while the flow rate of the steam entering through the orifice was almost the same. The liquid depth had a negligible effect on the vapor bubble formation in this experimental region. A model for describing the vapor bubble formation in the single-bubble region is presented. The predicted values from the present model using an explicit finite difference technique are compared with experimental data, and the results are in good agreement.