Pressure Drop and Compressible Flow of Cryogenic Liquid-Vapor Mixtures

1975 ◽  
pp. 229-259 ◽  
Author(s):  
R. E. Henry ◽  
M. A. Grolmes ◽  
H. K. Fauske
Keyword(s):  
Pressure Drop ◽  
Compressible Flow ◽  
Cryogenic Liquid ◽  
Vapor Mixtures ◽  
Liquid Vapor

Laminar Fully-Developed Flow in a Microchannel With Patterned Ultrahydrophobic Walls

2005 ◽  
Author(s):  
B. Woolford ◽  
K. Jeffs ◽  
D. Maynes ◽  
B. W. Webb
Keyword(s):  
Pressure Drop ◽  
Solid Wall ◽  
Relative Size ◽  
Frictional Resistance ◽  
Hydraulic Diameter ◽  
Fourth Power ◽  
Fully Developed Flow ◽  
Flowing Liquid ◽  
Frictional Pressure Drop ◽  
Liquid Vapor

Microfluidic transport is finding increasing application in a number of emerging technologies. At these scales, classical analysis shows that the required fluid driving pressure is inversely proportional to the hydraulic diameter to the fourth power. Consequently, generating fluid motion at these physical scales is a challenge. There is thus considerable incentive for developing strategies to reduce the frictional resistance to fluid flow. A novel approach recently proposed is fabrication of micro-ribs and cavities in the channel walls which are treated with a hydrophobic coating. This reduces the surface contact area between the flowing liquid and the solid wall, yielding walls with no-slip and shear-free regions at the microscale. The shear-free regions consist of a liquid-vapor meniscus above the cavities between micro-ribs. Reductions in the flow resistance are thus possible. This paper reports results of an analytical and experimental investigation of the laminar, fully-developed flow in a parallel plate microchannel whose walls are microengineered in this fashion. The micro-ribs and cavities are oriented parallel to the flow direction. The channel walls are modeled in an idealized fashion, with the shape of liquid-vapor meniscus approximated as flat and characterized by vanishing shear stress. Predictions are presented for the friction factor-Reynolds number product as a function of relevant governing dimensionless parameters. Comparisons are made between the smooth-wall classical channel flow results and predictions for the microengineered channel walls. Results show that significant reductions in the frictional pressure drop are possible. Reductions in frictional resistance increase as the channel hydraulic diameter and/or micro-rib width are reduced. The frictional pressure drop predictions are in good agreement with experimental measurements made at dynamically similar conditions, with greater deviation observed with increasing relative size of the shear-free regions.

Analysis on Liquid-Vapor Bubbly-Flow Systems in Reciprocating Motion

1999 ◽  
Vol 121 (1) ◽  
pp. 185-190 ◽  
Author(s):  
Claudia O. Iyer ◽  
Wen-Jei Yang
Keyword(s):  
Perturbation Technique ◽  
Bubbly Flow ◽  
Phase System ◽  
Neutral Stability ◽  
Reciprocating Motion ◽  
Two Phase ◽  
Shock Absorbers ◽  
The Laplace Transform ◽  
Vapor Mixtures ◽  
Liquid Vapor

An analytical study is performed on the dynamics and hydrodynamic stability of liquid-vapor mixtures in the bubbly-flow range in reciprocating motion through a horizontal channel. The perturbation technique is applied on the one-dimensional conservation equations for laminar flow and on the thermodynamic equation of state. The Laplace transform is operated on the linearized equations from which a transfer function is derived, relating the flow rate change due to a change in pressure drop along the channel. The resulting characteristic equation is analyzed to determine the dynamic behavior of the two-phase flow in reciprocating motion and the conditions for neutral stability under which self-induced oscillations occur. The natural frequency of the physical system is derived, which can be used to predict the resonance that will occur in forced vibrations. Results can be applied to systems such as car suspensions (shock absorbers) in which oil is susceptible to cavitation, resulting in bubbly flow due to vibrations. Conditions under which resonance occurs in the two-phase system are determined. Resonance leads to severe oscillations and noise generation, as experienced in shock absorbers in car suspensions.

Characterization of Flow Through Porous Metals

2013 ◽  
Author(s):  
Michael J. Hargather ◽  
Karen A. Thole
Keyword(s):  
Pressure Drop ◽  
Compressible Flow ◽  
Internal Flow ◽  
Porous Metal ◽  
Effective Diameter ◽  
Porous Metals ◽  
Flow Area ◽  
Flow Measurements ◽  
Flow Through

Porous metals have long been considered as an ideal material in which to manufacture turbine components given the inherent large convective surface area. One consideration, however, in using porous metals is the increase in pressure drop that accompanies these materials. To characterize increases in pressure drop for porous materials, flow measurements were made on numerous porous metal coupons. The porosity of the coupons investigated had a range of four in terms of density. A technique for determining the effective internal flow area from pressure drop measurements was developed to provide an effective diameter. The pressure drop measurements were compared to an ideal isentropic compressible-flow nozzle and to a smooth, straight-walled tube. The comparisons show that the porous channels have a similar, but much larger pressure drop than the smooth walls. The experiments performed demonstrated that these porous geometries can be scaled to provide generalized pressure drop characteristics for all geometries.

Heat Transfer and Pressure Drop Characteristics of Condensation for R410A in a 3.78mm Circular Tube Under Normal and Micro Gravity

2016 ◽  
Author(s):  
Jingzhi Zhang ◽  
Wei Li ◽  
Tom I.-P. Shih ◽  
Yonghai Zhang ◽  
Yanping Shi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Liquid Film ◽  
Thin Liquid Film ◽  
Transfer Coefficients ◽  
Bottom Part ◽  
Vapor Interface ◽  
Heat Transfer Coefficients ◽  
Micro Gravity ◽  
Liquid Vapor

Heat transfer and pressure drop characteristics of condensation for R410A inside horizontal tubes (dh = 3.78 mm) under normal and micro gravity are investigated numerically. The Volume of Fluid method is used to acquire liquid-vapor interface, while the low-Reynolds form of the Shear Stress Transport k∼ω (SST k∼ω) model is adopted to taking turbulent effect into account. The results indicate that the heat transfer coefficients decrease with increasing gravity accelerations, while the frictional pressure gradients increase with increases in gravity accelerations. The liquid film accumulates at the bottom of the tube, leading to a very thin liquid film attached to the upper part of inner tube wall. This accumulation effect decreases with decreases in gravitational accelerations. A more symmetrical liquid-vapor interface is obtained at lower gravity. The average liquid film thickness is nearly the same for different gravity accelerations at the same vapor quality (δave≈56 μm at x = 0.9 and δave≈230 μm at x = 0.5). The local heat transfer coefficients increase with increasing gravity at the top of the tube and decrease with increases in gravity at the bottom, while the bottom part of the tube has a limited contribution to the global heat transfer coefficient for stratified flow regime. The numerical data obtained under normal gravity agree well with well-known empirical correlations.

Experimental Study of Water Liquid-Vapor Two-Phase Pressure Drop Across an Array of Staggered Micropin-Fins

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Christopher A. Konishi ◽  
Weilin Qu ◽  
Frank E. Pfefferkorn
Keyword(s):  
Pressure Drop ◽  
Equivalent Diameter ◽  
Maximum Mass ◽  
Two Phase ◽  
Pin Fin ◽  
Friction Factor Correlation ◽  
Measured Pressure ◽  
Test Module ◽  
Phase Pressure ◽  
Liquid Vapor

This study concerns pressure drop of adiabatic water liquid-vapor two-phase flow across an array of 1950 staggered square micropin-fins having a 200×200 μm cross section by 670 μm height. The ratios of longitudinal pitch and transverse pitch to pin-fin equivalent diameter are equal to 2. An inline immersion heater upstream of the micropin-fin test module was employed to produce liquid-vapor two-phase mixture, which flowed across the micropin-fin array. The test module was well insulated to maintain adiabatic condition. Four maximum mass velocities of 184 kg/m2 s, 235 kg/m2 s, 337 kg/m2 s, and 391 kg/m2 s, and a range of vapor qualities for each maximum mass velocity were tested. Measured pressure drop increases drastically with increasing vapor quality. Nine existing two-phase pressure drop models and correlations were assessed. The Lockhart–Martinelli correlation for laminar liquid-laminar vapor combination in conjunction with a single-phase friction factor correlation proposed for the present micropin-fin array provided the best agreement with the data.

Experimental Study of Adiabatic Water Liquid-Vapor Two-Phase Pressure Drop Across an Array of Staggered Micro-Pin-Fins

2008 ◽  
Author(s):  
Christopher A. Konishi ◽  
Weilin Qu ◽  
Ben Jasperson ◽  
Frank E. Pfefferkorn ◽  
Kevin T. Turner
Keyword(s):  
Pressure Drop ◽  
Maximum Mass ◽  
Two Phase ◽  
Pin Fin ◽  
Pin Fins ◽  
Micro Pin Fins ◽  
Pin Fin Array ◽  
Test Module ◽  
Phase Pressure ◽  
Liquid Vapor

This study concerns pressure drop of adiabatic water liquid-vapor two-phase flow across an array of 1950 staggered square micro-pin-fins having a 200×200 micron cross-section by a 670 micron height. The ratios of longitudinal pitch and transverse pitch to pin-fin equivalent diameter are equal to 2. An inline immersion heater upstream of the micro-pin-fin test module was employed to produce liquid-vapor two-phase mixture, which flowed across the micro-pin-fin array. The test module was well insulated to maintain an adiabatic condition. Four maximum mass velocities of 184, 235, 337, and 391 kg/m2s, and a range of vapor qualities for each maximum mass velocity were tested. Measured pressure drop increases drastically with increasing vapor quality. Nine existing two-phase pressure drop models and correlations were assessed. The Lockhart-Martinelli correlation for laminar liquid-laminar vapor combination in conjunction with a single-phase friction factor correlation proposed for the present micro-pin-fin array provided the best agreement with the data.

Critical flow of liquid-vapor mixtures

AIChE Journal ◽  
1967 ◽  
Vol 13 (1) ◽  
pp. 52-60 ◽  
Author(s):  
James E. Cruver ◽  
R. W. Moulton
Keyword(s):  
Critical Flow ◽  
Vapor Mixtures ◽  
Liquid Vapor

Thermohydraulic Behavior of the Liquid–Vapor Flow in the Receiver Tube of a Solar Parabolic Trough Collector

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Sara Sallam ◽  
Mohamed Taqi
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Vapor Flow ◽  
High Heat Flux ◽  
Parabolic Trough ◽  
Convective Boiling ◽  
Flow Rates ◽  
Pressure Drops ◽  
Inlet Conditions ◽  
Liquid Vapor

Abstract Liquid–vapor flows are present in many industrial applications. In particular, in the solar field, these flows are encountered in the new generations of solar parabolic trough collectors with direct steam generation (PTCs-DSG). In this technical brief, we compare the two-phase convective transfer and the pressure drop models in the PTC-DSG. The results show that the heat exchange coefficients estimated by Chen–Cooper, Shah, Gungor–Winterton, and Kandlikar models have same trend with difference between them. However, the models of Liu–Winterton and Steiner–Taborek seem inappropriate due to the decrease in the exchange coefficient for moderate and high steam qualities. In addition, a comparison of the models describing pressure drops with experimental data of literature was carried out. The results show that the pressure decreases as the steam quality increases and the differences between these models remain small. Friedel's model is the closest to the experiment for high inlet pressures and flow rates, while Chisholm's model gives the best prediction of the pressure drop for low inlet conditions. Effect analysis of inlet conditions shows that the increase in inlet water mass flow and decrease in pressure favor convective heat transfer. The variation of heat flux on tube wall does not affect the convective boiling heat coefficient evaluated by the Chen–Copper model, whereas it influences the calculating coefficient by Gungor–Winterton model for high heat flux and particularly for low steam qualities. Pressure drops are higher at high flow rates and low pressures.

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