Two-phase pressure loss in terms of mixing length theory. 2. Comparison of model with upflow and downflow data

1985 ◽  
Vol 24 (4) ◽  
pp. 418-423 ◽  
Author(s):  
Nigel N. Clark ◽  
Rory L. C. Flemmer
Keyword(s):  
Pressure Loss ◽  
Mixing Length ◽  
Two Phase ◽  
Mixing Length Theory ◽  
Phase Pressure

Prediction of Two-Phase Pressure Drop and Density Distribution From Mixing Length Theory

1963 ◽  
Vol 85 (2) ◽  
pp. 137-150 ◽  
Author(s):  
S. Levy
Keyword(s):  
Single Phase ◽  
Continuous Medium ◽  
Phase System ◽  
Mixing Length ◽  
Test Results ◽  
Two Phase ◽  
Pressure Drops ◽  
Mixing Length Theory ◽  
Phase Pressure ◽  
Good Agreement

Single-phase turbulent mixing length methods are used to predict two-phase flow. Two-phase density and velocity distributions and two-phase pressure drops are derived by treating the two-phase system as a continuous medium where the turbulent exchanges of momentum and density are equal. Good agreement is obtained between test results and analytical predictions.

An Experimentally Validated Model for Two-Phase Sudden Contraction Pressure Drop in Microchannel Tube Headers

2003 ◽  
Author(s):  
John Wesley Coleman
Keyword(s):  
Pressure Loss ◽  
Accurate Determination ◽  
Time Data ◽  
Two Phase ◽  
Pressure Transducers ◽  
Pressure Losses ◽  
Mass Fluxes ◽  
Data Points ◽  
Minor Losses ◽  
Phase Pressure

This paper presents the results of an experimental investigation of two-phase pressure loss of R134a in microchannel headers using various end-cut techniques. Novel experimental techniques and test sections were developed to enable the accurate determination of the minor losses without obfuscating the problem with a lengthwise pressure gradient. This technique represents a departure from approaches used by other investigators that have extrapolated minor losses from air-water experiments and the combined effects of expansion, contraction, deceleration, and lengthwise pressure gradients. Pressure losses were recorded over the entire range of qualities from 100% vapor to 100% liquid. In addition, the tests were conducted for five different refrigerant mass fluxes between 185 kg/m2-s and 785 kg/m2-s using two differnt end-cut techniques. More than 790 data points were recorded to obtain a comprehensive understanding of the effects of mass flux and quality on minor pressure losses. High accuracy instrumentation such as coriolis mass flowmeters, RTDs, pressure transducers, and real-time data analyses were used to ensure accuracy in the results. The results show that many of the commonly used correlations for estimating two-phase pressure losses significantly underpredict the pressure losses found in compact microchannel tube headers. Furthermore, the results show that the end-cut technique can substantially affect the pressure losses in microchannel headers. A new model for estimating the pressure loss in microchannel headers is presented and a comparison of the end-cut techniques on the minor losses is reported.

Application of Mixing Length Theory to Wavy Turbulent Liquid—Gas Interface

1981 ◽  
Vol 103 (3) ◽  
pp. 492-500 ◽  
Author(s):  
S. Levy ◽  
J. M. Healzer
Keyword(s):  
Liquid Film ◽  
Transition Layer ◽  
Volume Fraction ◽  
Density Ratio ◽  
Constant Density ◽  
Mixing Length ◽  
Two Phase ◽  
Liquid Entrainment ◽  
Wide Range ◽  
Mixing Length Theory

A fully developed and adiabatic two-phase annular model with liquid entrainment is derived for flow in a pipe with negligible gravity effects. The model is based upon application of the single phase mixing length theory to a wavy liquid-gas interface. The model subdivides the flow cross section into three regions: a liquid film, a gas core of constant density, and a transition wavy layer between them. The combination of a constant velocity and a density varying exponentially with distance from the wall is employed in the transition layer. This approach plus appropriate logarithmic velocity distributions in the liquid film and gas core make it possible to specify the two-phase pressure drop, volume fraction, wave velocity, and thickness of the liquid film and transition layer. The liquid entrainment is obtained in terms of the exponent of the density profile in the transition layer, and interface stability considerations are used to express this entrainment parameter semiempirically in terms of an apparent Weber number and density ratio. Comparisons of the model are made with air-water and steam-water test data, and the results generally are satisfactory over a wide range of conditions and for all the important characteristics of this flow pattern.

A Review of Prediction Methods for Two-Phase Pressure Loss in Mini/Micro-Channels

2016 ◽  
Vol 24 (01) ◽  
pp. 1630002 ◽  
Author(s):  
Jung Hoon Yun ◽  
Ji Hwan Jeong
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Pressure Loss ◽  
Separated Flow ◽  
Empirical Correlations ◽  
Two Phase ◽  
Flow Models ◽  
Micro Channels ◽  
Extensive Experimental Data ◽  
Phase Pressure

Previous methods and correlations for predicting two-phase frictional pressure loss in mini/micro-channels are reviewed and compared. The empirical correlations are classified into four groups of modeling approaches: Homogeneous equilibrium models (HEMs), separated flow models (SFMs), direct empirical correlations, and flow pattern specific correlations. In order to examine the characteristics of the predictive methods for two-phase pressure loss in mini-channels and to assess the accuracy of the previous models and correlations, extensive experimental data and correlations that are available in the open literature are collected. The 1175 and 1304 experimental data for the two-phase pressure drop for condensing and boiling flows, respectively, are gathered from 15 papers and reports. The results present that the size of the channel significantly influences the pressure drop. The comparison demonstrates that Cicchitti et al.’s two-phase viscosity model is recommended for predicting two-phase pressure loss when the HEM is used. In general, the SFM with the two-phase multipliers of Muller–Steinhagen and Heck and Kim and Mudawar outperforms others for channel diameters of less than 3[Formula: see text]mm.

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