Amplitude characteristics of pressure oscillation caused by steam jet condensation in a confined channel

Abstract

Steam jet injector is a prospective device with advantages of impact volume, strong heat transfer, without moving part, which can be applied in various industrial fields such as nuclear/conventional power plant, heat-supply system and heat recovery system, etc. However, as the steam jet injector is driven by high speed steam jet condensation in subcooled water flow in the mix chamber, the instability of steam-water direct contact condensation will lead to loud noise and severe vibration. Thus, loud noise will evolve into environmental pollution, and vibration will endanger the equipment, which prevent the promotion of this device in induatrial applications. Moreover, the published works generally involved in the pressure oscillation caused by steam jet condensation in large space water pool, where the water was considered to be stagnant. However, the case becomes more complex when direct contact condensation occurs in a confined channel like in a steam jet injector, where the effect of turbulence on water side and wall can not be ignored. Thus, the reported results can not be applied in the present condition. So it is necessary to study the mechanism of the instability of steam-water direct contact condensation in a confined channel. In this paper, experimental investigation was performed on the amplitude characteristics of pressure oscillation caused by direct contact condensation in a confined channel, aiming at revealing the mechanism of noise and vibration and providing some guidance for the design and operation of the steam jet injector. In order to better observe the behavior of the steam-water interface, a special visualized test section was designed and a high speed camera was applied. The dynamic pressure data was obtained by a dynamic pressure transducer arranged on the wall of channel. Three main inlet parameters, including steam mass flux, water mass flux and water temperatures were tested in the ranges of 150–600 kg/m2s, 6×103–18×103 kg/m2s and 15–40°C, respectively. The results indicated that when direct contact condensation occurred in a confined channel, flow patterns could be divided into two categories-unstable and stable flow patterns with respect to the interface behavior. The effect of the inlet parameters on amplitude characteristics of pressure oscillation was discussed. With the increase of water mass flux, the amplitude altered slightly in stable flow pattern region, but increased suddenly and dramatically in unstable region. With the increase of steam mass flux, the amplitude increased a little in unstable region, but decreased suddenly in stable region and then increased again. And the increase of water temperature leaded to the increasing of amplitude in all flow pattern regions. In a word, the equipment would bear stronger impact load when operating in unstable flow pattern region.