TWO-PHASE FLUID FLOW
Fluid Flow
Summary
The main points from this chapter are summarized below.
Two-Phase Fluid Flow Summary
The combination of liquid and vapor flowing through a pipe is called two-phase
flow.
Types of two-phase flow include:
• Bubbly flow: there is a dispersion of vapor bubbles in a continuum of liquid.
• Slug flow:
the bubbles grow by coalescence and ultimately become of the
same order of diameter as the tube, generating bullet shaped
bubbles.
• Annular flow: the liquid is distributed between a liquid film flowing up the wall
and a dispersion of droplets flowing in the vapor core of the
flow.
Core flow oscillations and instabilities can cause:
• undesirable mechanical vibration of components.
• a reduction in the heat flux required to cause DNB.
• interruptions to actual circulation flow.
Flow oscillations and instabilities can occur during the following conditions:
• core is outside design conditions, power > 150%
• mechanical failure, causing flow blockage
• inadequate core cooling during natural circulation, such that boiling is occurring
Pipe whip is the displacement of piping created by the reaction forces of a high
velocity fluid jet following a pipe rupture.
Water hammer is a liquid shock wave resulting from a sudden starting or stopping
of flow.
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