TWO-PHASE FLUID FLOW

Thermodynamics Heat Transfer and Fluid Flow Volume 3 of 3
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Fluid Flow TWO-PHASE FLUID FLOW TWO-PHASE FLUID FLOW Water at saturation conditions may exist as both a fluid and a vapor. This mixture of steam and water can cause unusual flow characteristics within fluid systems. EO 1.31 DEFINE two-phase flow. EO 1.32 DESCRIBE two-phase flow including such phenomena as bubbly, slug, and annular flow. EO 1.33 DESCRIBE the problems associated with core flow oscillations and flow instability. EO 1.34 DESCRIBE the conditions that could lead to core flow oscillation and instability. EO 1.35 DESCRIBE the phenomenon of pipe whip. EO 1.36 DESCRIBE the phenomenon of water hammer. Two-Phase Fluid Flow All of the fluid flow relationships discussed previously are for the flow of a single phase of fluid whether liquid or vapor. At certain important locations in fluid flow systems the simultaneous flow of liquid water and steam occurs, known as two-phase flow. These simple relationships used for analyzing single-phase flow are insufficient for analyzing two-phase flow. There are several techniques used to predict the head loss due to fluid friction for two-phase flow. Two-phase flow friction is greater than single-phase friction for the same conduit dimensions and mass flow rate. The difference appears to be a function of the type of flow and results from increased flow speeds. Two-phase friction losses are experimentally determined by measuring pressure drops across different piping elements. The two-phase losses are generally related to single-phase losses through the same elements. One accepted technique for determining the two-phase friction loss based on the single-phase loss involves the two-phase friction multiplier (R), which is defined as the ratio of the two-phase head loss divided by the head loss evaluated using saturated liquid properties. (3-18) R H_f , two phase H_f , saturated liquid Rev. 0 Page 41 HT-03

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