Dealing with two-phase flows
- AEA Technology, Harwell (United Kingdom)
Gas- and vapor-liquid flows through pipework or equipment often pose major difficulties in both design and operation. Typically, two-phase fluid systems are susceptible to flow instabilities, blockages, and pressure and temperature fluctuations. As a result, gas-liquid flows are avoided whenever possible by separating the two phases into individual streams of nearly homogeneous gas and liquid. However, certain process conditions require or inevitably produce two phases. Examples include condensate-return lines flashing into steam, vapor-liquid feed lines entering distillation columns, and refrigerant-return lines that must maintain a specific vapor-liquid ratio for efficient operation. The thermohydraulic behavior of two-phase systems includes variations in pressure drop, flow patterns, and liquid holdup or void fraction. Increasing the pipe diameter reduces the pressure drop for a given flowrate, or alternatively produces an increase in the flowrate for a given pressure drop in a piping system. However, increased pipeline diameters lead to higher costs, and may require installation of more expensive equipment to accommodate the resulting larger slug volumes. There have been numerous improvements in correlations and methods for the prediction of pressure drop in gas-liquid flows. A few of them attempt to take into account the highly complex flow structure of a two-phase flow. One must keep in mind that the flow structure varies with time and position in the pipework. The paper discusses empirical correlations, pressure drop due to friction, gravity, and acceleration, transitions in flow patterns, liquid inventories, and erosion. 46 refs.
- OSTI ID:
- 70001
- Journal Information:
- Chemical Engineering, Vol. 102, Issue 6; Other Information: PBD: Jun 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Horizontal two-phase flow of gases and non-Newtonian liquids
Comparison of two phase liquid holdup and pressure drop correlations across flow regime boundaries for horizontal and inclined pipes