Gas–liquid two-phase flow in microchannels: Part II: void fraction and pressure drop

Providing a comprehensive introduction to the fundamentals and applications of flow and heat transfer in conventional and miniature systems, this fully enhanced and updated edition covers all the topics essential for graduate courses on two-phase flow, boiling, and condensation. Beginning with a concise review of single-phase flow fundamentals and interfacial phenomena, detailed and clear discussion is provided on a range of topics, including two-phase hydrodynamics and flow regimes, mathematical modeling of gas-liquid two-phase flows, pool and flow boiling, flow and boiling in mini and microchannels, external and internal-flow condensation with and without noncondensables, condensation in small flow passages, and two-phase choked flow. Numerous solved examples and end-of-chapter problems that include many common design problems likely to be encountered by students, make this an essential text for graduate students. With up-to-date detail on the most recent research trends and practical applications, it is also an ideal reference for professionals and researchers in mechanical, nuclear, and chemical engineering.

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Two-phase flow, boiling and condensation in conventional and miniature systems

Pressure drop caused by abrupt flow area changes in small channels

Segmented gas–liquid flow characterization in rectangular microchannels

An improved method and apparatus for filtration includes an outer stationary body (10), an inner rotating body (12) defining a gap with the outer body for receiving a fluid sample (14), the surface of one of the bodies defining the gap being a filter. The rotation of the inner body creates Taylor vortice which continuously displace occluded solute on the filter surface. The filter can be a membrane.

Filtration method and apparatus

Two-phase pressure drop across sudden contractions in duct areas

Critical two-phase flow through rough slits

Pressure drop during gas/vapour-liquid flow in pipes. Pressure drop in two phase flow is considered to be made up of terms for geodetical elevation or depression, acceleration, and friction. The geodetical and momentum pressure drop are discussed and reasonable correlations are presented, along with their limitations and range of application. Various relationships are available for calculating the technically important friction component. However, such predictions are still relatively inexact. If purely empirical correlations are neglected, all the remaining predictive schemes can be related to three basic physical models. These models as well as the commonly accepted and most reliable relationships are discussed and classified according to type. Furthermore, their scope is defined and the accuracy of prediction systematically compared with the aid of a newly set-up data bank. The extensive literature data consulted refer to single component two phase flow of water and various refrigerants and several two-component systems in horizontal and vertical unheated straight pipes under industrially relevant flow conditions. Finally, the accuracy of the prediction of some generally accepted void correlations is dealt with; here too, numerous published void fraction data have been gathered and checked.

Druckabfall bei der Strömung von Gas/Dampf‐Flüssigkeits‐Gemischen in Rohren

The throat-to-stagnation critical pressure ratio for a frictionless and adiabatic nozzle flow of a homogeneous, nonflashing two-phase mixture can only be expressed as the numerical solution of a transcendental equation. A simple, physically plausible approximation is herein proposed, which fits well over the whole range of mass flow qualities.

Explicit Critical Pressure Ratio for Choked Two‐Phase Homogeneous Nozzle Flow

The predictions of a new model for the contraction coefficient of single- and two-phase flows through a sharp-edged short orifice are checked against data recently obtained with water, air, and air/water mixture flows. The model includes all relevant primary design parameters. The predictions are validated for a wide range of conditions and physical properties typically encountered in industrial fluid-dynamic systems. Calculations based on the new model are sufficiently accurate for engineering purposes. Reasonable extrapolations to other test conditions with an acceptable accuracy can be expected.

Lutz Friedel

Papers

Two-phase pressure drop across sudden contractions in duct areas

Critical two-phase flow through rough slits

Druckabfall bei der Strömung von Gas/Dampf‐Flüssigkeits‐Gemischen in Rohren

Explicit Critical Pressure Ratio for Choked Two‐Phase Homogeneous Nozzle Flow

Prediction of Single‐ and Two‐Phase Flow Contraction through a Sharp‐Edged Short Orifice