Two-Phase Slug Flow in a Concentric Annulus with a Rotating Inner Cylinder

Gas-liquid two-phase slug in a concentric annulus with a rotating inner cylinder has been experimentally investigated. The flow patterns identified on the basis of visual observations are classified into four categories, i.e., slug flow, spiral-slug flow, peripherally elongated slug flow and ring-form slug flow. Such a flow regime map is expressed as a function of the total volumetric flux and the rotational speed. The rising velocity of a large bubble approximately coincides with Nicklin et al.\u27s correlation at relatively low rotational speed, while the rising velocity is lower than that of Nicklin et al.\u27s correlation at high rotational speed. This is closely related to the void fraction distribution along the radial direction in the annulus. The ratio of the kinetic energy loss to the potential one in the slug flow regime is well correlated by a linear function of the volumetric flux ratio of two phases as in the case of a bubbly flow regime. This ratio of energy losses is well expressed using the drift-flux model modified by taking into account the large bubble size in the annulus

Flow Instabilities in Boiling Channels : Part 1 Pressure Drop Oscillation

The pressure drop oscillation in a boiling channel system was analyzed by using a lumped parameter model in which the pressure drop characteristics was described by a third order equation of the flow rate. The momentum equation in the boiling channel system was thus reduced to a Van der Pol equation. The limit cycle and the period of the pressure drop oscillation obtained from the Van der Pol equation agreed qualitatively with experimental results

Flow Instabilities in Boiling Channels : Part 2 Geysering

An experimental study on geysering was carried out in an R-113 forced flow boiling system. The effects of flow rate, heat flux density, system pressure and heating condition on the threshold of geysering and on the period and amplitude of the differential pressure at the test section were studied. The mechanism of geysering was analyzed by using a simple model. The analytically predicted period and amplitude of oscillation agreed qualitatively with the experimental results and thus supported the validity of the model

Flow Instabilities in Boiling Channels : 3rd Report. Experimental Results in Multi-Channel System

蒸発管相互の干渉が特に顕著な少数並列管で発生する密度波振動、フローパターン遷移不安定、圧力降下振動および流量の再分配について述べる。本報では各管の熱・水力学的特性が一様な場合を対象としている。脈動のモードと位相関係、圧力効果特性と脈動の関係を明らかにし、操作パラメータを加熱量とした場合と流量とした場合に得られる特性曲線の関係についても述べる