Technology & Engineering
Flow Regime
Flow regime refers to the characteristic behavior of fluid flow within a system, often categorized based on factors such as velocity, density, and viscosity. It helps engineers and technologists understand and predict how fluids will behave under different conditions, enabling the design and optimization of systems such as pipelines, channels, and heat exchangers.
Written by Perlego with AI-assistance
Related key terms
1 of 5
3 Key excerpts on "Flow Regime"
eBook - PDF- Geoffrey Hewitt(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
These indexes will assist the reader in finding a wider range of references on many other topics which are only briefly reviewed in this book. 2.4. Flow Regime maps The usual way of presenting results of observations of flow patterns is to plot them on a graph whose axes represent the flowrates of the two phases; an alternative is to plot total mass flux (total mass flowrate divided by total flow area) on one axis and the mass fraction 8 Annular Two-Phase Flow of the flow which is vapour or gas on the other axis. When all the observations have been recorded in the manner appropriate, lines are drawn on the graph to represent the boundaries between the various regimes of flow. The resultant diagram is called a flow pattern map or a Flow Regime map. Some Flow Regime maps attempt to take account of channel geometry and fluid physical properties by suitable adaptation of the parameters which are plotted. There are many such maps available and it is unnecessary to describe all of them in the present text. However, the reader who wishes to have further information about the existing flow pattern diagrams should consult the report by Vohr (1960) which gives a literature survey on this topic. Some useful comments on this subject are also made by Scott (1963). For the present purposes, two maps will be presented—one for horizontal flow and the other for vertical flow. These serve to illustrate the approach and, at the same time, gives a ready source from which the flow patterns, occurring in any particular application, may be calculated (at least, approximately). For horizontal flow, the best-known and most widely used Flow Regime map is that of Baker (1954). The Baker chart, as modified by Scott (1963), is shown in Fig.
eBook - PDF- Thomas J. Hanratty(Author)
- 2013(Publication Date)
- Cambridge University Press(Publisher)
2 Flow Regimes 2.1 Need for a phenomenological understanding The one-dimensional analysis and the correlations for frictional pressure drop and void fraction (presented in Chapter 1) have been widely used as a starting point for engineer- ing designs. However, these correlations have the handicap that the structure of the phase boundaries is ignored. As a consequence, they often give results which are only a rough approximation and overlook phenomena which could be of first-order importance in understanding the behavior of a system. It is now recognized that the central issue in developing a scientific approach to gas– liquid flows is the understanding of how the phases are distributed and of how the behavior of a multiphase system is related to this structure (Hanratty et al., 2003). Of particular interest is the finding that macroscopic behavior is dependent on small-scale interactions. An example of this dependence is that the presence of small amounts of high molecular weight polymers can change an annular flow into a stratified flow by damping interfacial waves (Al-Sarkhi & Hanratty, 2001a). A goal of this book is to develop an understanding of the basic scientific tools needed to describe gas–liquid flows. This chapter opens this discourse by describing flow patterns that have been defined. Detailed discussions of the theory will be presented in later chapters. Four systems are considered: flow in horizontal pipes, flow in vertical pipes, micro- gravity flows, flow in capillaries and microchannels. Discussions of the flow regimes in horizontal pipes and of the mechanisms for transitions from one regime to another provide the motivation for a large portion of this book. The Kelvin–Helmholtz (inviscid) instability of a stratified flow plays an important role in understanding gas–liquid flows.
eBook - PDFTwo-Phase Flow, Boiling, and Condensation
In Conventional and Miniature Systems
- S. Mostafa Ghiaasiaan(Author)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
(2) Empirical Flow Regime maps often attempt to specify parameter ranges for vari-ous Flow Regimes using a common set of coordinates. Since the mechanisms that cause various regime transitions are different, a common set of coordinates may not be appropriate for the entire Flow Regime map. (3) Most Flow Regime maps are based on data obtained with water, or liquids whose properties are not significantly different from those of water, in channels with diameters in the 1–10 cm range. The maps may not be useful for significantly different channel sizes or fluid properties. (4) Closure relations are necessary for the solution of conservation equations (e.g., interfacial area concentration, interfacial forces, and transfer process rates, etc.) and these closure relations depend on Flow Regimes. A Flow Regime change thus implies switching from one set of correlations and models to another. This can introduce discontinuities and can cause numerical difficulties. This difficulty is mitigated to some extent by defining Flow Regime transition zones. Problems 159 Two-phase Flow Regimes will be further discussed in Chapter 7 , after the two-phase model conservation equations are discussed in the next chapter . PROBLEMS 4.1 Saturated liquid R-134a is flowing in a vertical heated tube that has a diameter of 1 cm. The pressure is 16.8 bar, which remains approximately constant along the tube. A heat flux of 100 kW/m 2 is imposed on the tube. (a) Assuming that friction and changes in kinetic and potential energy are negligible, prove that the first law of thermodynamics leads to G dx eq dz = 4 q w Dh fg , where z is the axial coordinate. (b) Assuming the Flow Regime maps based on adiabatic flow apply, using the Flow Regime map of Hewitt and Roberts ( 1969 ) determine the sequence of two-phase Flow Regimes and the axial coordinate where each regime is established for the following mass fluxes: G = 200, 500, and 1500 kg/m 2 · s.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
