Bubble formation and heat transfer during dispersion of superheated steam in saturated water—I: Bubble size and bubble detachment at single orifices

Abstract

Despite the high practical importance of heat and mass transfer between fluid phases the relevant data are not well known due to the multitude of parameters affecting this phenomenon. This paper deals with part of this extended problem by restriction on the events taking place during bubble formation at single orifices. Subject of this paper is the experimental investigation of bubble formation and detachment from single submerged orifices at high system pressures and temperatures. In Part II the corresponding heat transfer is investigated. The experiments are carried out in the steam-water system. The superheated steam is injected through 1.5, 2 and 3 mm diameter orifices from a 5 cm 3 antechamber into demineralized saturated water. The steam flow rate is varied in the range of 2–20 g/min, the maximum pressure is 212 at. The examinated steam temperature differences related to the corresponding boiling temperatures are 100, 150 and 200 K. The experimental observations are interpreted by means of dimensional analysis. The following results are obtained: Relations are pointed out between the bubble shape as well as the formation frequency and the physical parameters of the system. The relevant effect on transition from steady-state bubble formation (single bubble formation) to unsteady-state bubble formation (coalescence of the bubble during detachment) is found to be a problem of eigenoscillation of the bubble.