Experimental investigations of the interface between steam and water two phase flows

Abstract

a b s t r a c tHydrodynamic instabilities play an important role in the design of those systems operated at high temperature and pressure. The creation and propagation of Kelvin-Helmholtz (KH) instabilities has been experimentally investigated here for the first time in condensable fluids i.e. steam and water. Generally, in case of these condensable fluids the instabilities are so much short lived that it's very difficult to record them. Here the instabilities occurred in the close vicinity of the steam-water interface, were attributed mainly to the temperature fluctuations of micro scale or less. Supersonic steam was injected inside the subcooled water at inlet pressure varying from 1.5 bar to 3.0 bar by using a specially designed supersonic nozzle, whereas temperature of water inside the vessel was raised from 30°C to 60°C at an increment of 50 each. Kelvin-Helmholtz instabilities in the form of minor as well as amplified transient temperature fluctuations were recorded using a specially designed apparatus that uses LM35 sensors and data acquisition system. This system is capable to record temperatures at a rate of one millisecond and was also capable to record the temperatures anywhere inside the vessel. It was also found out that the instabilities created at the interface propagated towards the axis of the geometry as well as these instabilities were strongly affected by change in tank water temperature and inlet pressure.

Determining potential of subcooling to attenuate hydrodynamic instabilities for steam–water two phase flow

“…Kelvin-Helmholtz instabilities were observed and reported first time in case of supersonic steam jet interaction with subcooled water [3]. These instabilities were observed against an inlet pressure of 1.5 bars for steam that varied up to 3.0 bars, whereas the temperature of water was kept at a temperature range of 30-60°C, with an step increase of 5°C till it reached to 60°C.…”

“…The first case of temperature profile that attracted attention to study the effect of subcooling on the attenuation of Kelvin-Helmholtz instabilities was the one where temperature was reduced from 60°C to 30°C at a constant inlet pressure of 1.5 bars as shown in Fig. 10 [3].…”

“…The KH hydrodynamic instabilities as borne due to the temperature fluctuations along radial direction are shown in Fig. 17 [3].…”

“…The creation and propagation of hydrodynamic instabilities in case of high pressure and mass flow rate steam injection is an obvious fact which is further http://dx.doi.org/10.1016/j.ijheatmasstransfer.2014.12.073 0017-9310/Ó 2015 Elsevier Ltd. All rights reserved. supported by Khan et al [3]. They performed experimentation to investigate the creation and propagation of KH hydrodynamic instabilities at 1.5 bars of gauge pressure.…”

“…As these instabilities are very small, short lived and very transient in nature so to the date as best known to the authors of this work, the research on topic is scarce. Keeping the fact in mind that being playing an active role in causing of almost one third of the events [1] and showing their emergence even at very low inlet steam pressure of 1.5 bars [3] gauge pressure, Kelvin-Helmholtz hydrodynamic instabilities exist wherever steam comes into contact with the water. So we cannot simply negate their importance and a more vital importance of the research, which can guide the scientific community towards pursuit of the most dominant parameter responsible for effective attenuation of these instabilities.…”