Abstract
ABSTRACTAn experimental investigation of adiabatic upward co‐current air–water two‐phase flow has been carried out to determine the flow patterns in a 12.2=m‐high and 250=mm nominal diameter vertical pipe. The visual observations of flow patterns were supplemented by statistical analysis of the time‐averaged void fraction determined by pressure drop method. Four flow patterns were identified in the vertical test section, namely dispersed bubbly, bubbly, agitated bubblyand churn/forth flow within the experimental superficial velocity range ( ja = 0.18–2.2 m/s and jw = 0.18–1.2 m/s). Conventional slug flow consisting of smooth bullet‐shaped bubbles (Taylor bubble) and liquid slugs was never observed; instead, agitated bubbly flow was the most dominant flow pattern in relevant superficial velocity range. On the basis of the visual and statistically extracted information, a flow pattern map was developed and compared with the existing flow pattern maps. Available flow regime transition models compared against the present experimental data yielded poor agreement with none of the existing models predicting the transitions as a whole. A satisfactory agreement was obtained with other large diameter studies with inconsistencies mainly attributable to confusion in the identification of the flow patterns. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.
Highlights
Two phase flow in pipes is frequently encountered in various industrial processes, such as petroleum, nuclear, chemical, power generation, refrigeration etc
It is found that little studies of two phase flow in large diameter vertical pipes have been conducted and the vertical two-phase flow in large diameter pipes is still not well understood
In the above studies, it is noted that either, the way two phases are introduced in the vertical pipe were given in the vague way, if not entirely omitted or the gas distributor configurations were entirely different than the configurations encountered in industrial conditions. These studies do not include the industrial effect of the flow path which is typical for applications like process industry where gas inlet to vertical pipe is (i) a 90o smaller diameter pipe at the base or (ii) both gas-liquid phase flowing in long horizontal pipe attached to vertical pipe base via elbow
Summary
Two phase flow in pipes is frequently encountered in various industrial processes, such as petroleum, nuclear, chemical, power generation, refrigeration etc. In the above studies, it is noted that either, the way two phases are introduced in the vertical pipe were given in the vague way, if not entirely omitted or the gas distributor configurations (porous plates, perforated plates/rings, porous tubes multiple/single-orifice plates, nozzle, shower caps discs or porous sinter walls etc.) were entirely different than the configurations encountered in industrial conditions These studies do not include the industrial effect of the flow path which is typical for applications like process industry where gas inlet to vertical pipe is (i) a 90o smaller diameter pipe at the base or (ii) both gas-liquid phase flowing in long horizontal pipe attached to vertical pipe base via elbow (e.g. horizontal flowline connected to vertical pipe in oil & gas exploration or hot leg of a nuclear reactor or once through steam generator that have a certain inlet pipe/configuration connected to a vertical pipe). The results presented here are useful in extending the knowledge of two-phase flow behaviour in large diameter vertical pipe in general and can be regarded as a first hand tool for knowing the flow patterns and the approximate transitions in large diameter vertical pipe
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