Coupled Liquid and Vapor Flow in Miniature Passages With Micro Grooves

1999 ◽  
Vol 121 (3) ◽  
pp. 729-733 ◽  
Author(s):  
D. Khrustalev ◽  
A. Faghri
Keyword(s):  
Liquid Flow ◽  
Shear Stresses ◽  
Vapor Flow ◽  
Two Phase ◽  
Interface Shear ◽  
Element Analysis ◽  
Vapor Interface ◽  
Vapor Channel ◽  
Frictional Interaction ◽  
Liquid Vapor

Friction factor coefficients for liquid flow in a rectangular micro-groove coupled with the vapor flow in a vapor channel of a miniature two-phase device were calculated using finite element analysis. The results show that the effect of the vapor-liquid frictional interaction on the liquid flow decreases with curvature of the liquid-vapor interface. Shear stresses at the liquid-vapor interface are significantly nonuniform, decreasing towards the center of the liquid-vapor meniscus.

Prediction of Laminar Flow in a Microchannel With Transverse Ultrahydrophobic Ribs

2005 ◽  
Author(s):  
J. Davies ◽  
B. Woolford ◽  
D. Maynes ◽  
B. W. Webb
Keyword(s):  
Friction Factor ◽  
Liquid Flow ◽  
Frictional Resistance ◽  
Vapor Flow ◽  
Flowing Liquid ◽  
Vapor Cavity ◽  
Vapor Interface ◽  
Smooth Channel ◽  
The Impact ◽  
Liquid Vapor

One approach recently proposed for reducing the frictional resistance to liquid flow in microchannels is the patterning of micro-ribs and cavities on the channel walls. When treated with a hydrophobic coating, the liquid flowing in the microchannel wets only the surfaces of the ribs, and does not penetrate the cavities, provided the pressure is not too high. The net result is a reduction in the surface contact area between channel walls and the flowing liquid. For micro-ribs and cavities that are aligned normal to the channel axis (principal flow direction), these micro-patterns form a repeating, periodic structure. This paper presents experimental and numerical results of a study exploring the momentum transport in a parallel plate microchannel with such microengineered walls. The liquid-vapor interface (meniscus) in the cavity regions is treated as ideal in the numerical analysis (flat). Two conditions are explored with regard to the cavity region: 1) The liquid flow at the liquid-vapor interface is treated as shear-free (vanishing viscosity in the vapor region), and 2) the liquid flow in the microchannel core and the vapor flow within the cavity are coupled through the velocity and shear stress matching at the interface. Predictions and measurements reveal that significant reductions in the frictional pressure drop can be achieved relative to the classical smooth channel Stokes flow. Reductions in the friction factor are greater as the cavity-to-rib length ratio is increased (increasing shear-free fraction) and as the channel hydraulic diameter is decreased. The results also show that the average friction factor – Reynolds number product exhibits a flow Reynolds dependence. Furthermore, the predictions reveal the impact of the vapor cavity regions on the overall frictional resistance.

Complete Condensation of Forced Convection Two-Phase Flow in a Miniature Tube

1999 ◽  
Vol 121 (4) ◽  
pp. 904-915 ◽  
Author(s):  
E. Begg ◽  
D. Khrustalev ◽  
A. Faghri
Keyword(s):  
Two Phase Flow ◽  
Film Condensation ◽  
Vapor Flow ◽  
Pressure Jump ◽  
Phase Flow ◽  
Two Phase ◽  
Vapor Interface ◽  
Complete Condensation ◽  
Annular Film ◽  
Liquid Vapor

A physical and mathematical model of annular film condensation in a miniature tube has been developed. In the model the liquid flow has been coupled with the vapor flow along the liquid-vapor interface through the interfacial temperature, heat flux, shear stress, and pressure jump conditions due to surface tension effects. The model predicts the shape of the liquid-vapor interface along the condenser and the length of the two-phase flow region. The numerical results show that complete condensation of the incoming vapor is possible at comparatively low heat loads. Observations from a flow visualization experiment of water vapor condensing in a horizontal glass tube confirm the existence and qualitative features of annular film condensation leading to the complete condensation phenomenon in small diameter (d < 3.5 mm) circular tubes.

Two Phase Flow Patterns and Cooling Power of Mixed Refrigerant in Micro Cryogenic Coolers

2012 ◽  
Author(s):  
Ryan Lewis ◽  
Hayley Schneider ◽  
Yunda Wang ◽  
Ray Radebaugh ◽  
Y. C. Lee
Keyword(s):  
Liquid Flow ◽  
High Speed ◽  
Single Phase ◽  
Liquid Fraction ◽  
Cryogenic Cooling ◽  
Cooling Power ◽  
Vapor Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Power Draw

Micro cryogenic coolers (MCCs) operating in the Joule-Thomson cycle with mixed refrigerants offer an attractive way to decrease the size, cost, and power draw required for cryogenic cooling. Recent studies of MCCs with mixed refrigerants have, when employing pre-cooling, shown pulsating flow-rates and oscillating temperatures, which have been linked to the refrigerant flow regime in the MCC. In this study we investigate those flow regimes. Using a high-speed camera and optical microscopy, it is found that the pulsations in flow correspond to an abrupt switch from single-phase vapor flow to single-phase liquid flow, followed by 2-phase flow in the form of bubbles, liquid slugs, and liquid slug-annular rings. After this period of 2-phase flow, the refrigerant transitions back to single-phase vapor flow for the cycle to repeat. Under different pre-cooling temperatures, the mole fraction of the vapor-phase refrigerant, as measured by molar flow-rate, agrees reasonably well with the quality of the refrigerant at that temperature as calculated by an equation of state. The frequency of pulsation increases with liquid fraction in the refrigerant, and the volume of liquid in each pulse only weakly increases with increasing liquid fraction. The cooling power of the liquid-flow is up to a factor of 7 greater than that of the 2-phase flows and single-phase vapor flow.

Prediction of the Transport Phenomena in the Micro Capillary Tube of a CPL System

2003 ◽  
Author(s):  
Kyoungwoo Park ◽  
Kwan-Soo Lee
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Capillary Tube ◽  
Transport Phenomena ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Phase ◽  
Vapor Interface ◽  
Meniscus Region ◽  
Liquid Vapor

A mathematical model is presented to predict the two-phase transport phenomena of the evaporating extended meniscus region in a micro capillary tube which approximates the evaporator of the CPL system. The behavior of a liquid-vapor interface can be estimated by using the augmented Laplace-Young equation. The governing equations for transport fields of liquid and vapor phases can be obtained by adopting the different physical approaches for the meniscus and thin film regions. In this model, the variation of vapor pressure and the disjoining pressure effect are included and the friction force at the liquid-vapor interface is also considered. The results show that the local heat transfer coefficient has an extremely large value in the thin film region. However, the amount of heat transfer rate, of the meniscus region is larger than that of the thin film region. It is also found that the length of the extended meniscus region is affected by the heat flux, the tube radius and the dispersion constant.

Visualization of Confined Jet Impingement With Boiling Using Time-Resolved Stereo-PIV

2015 ◽  
Author(s):  
Matthew J. Rau ◽  
Tianqi Guo ◽  
Pavlos P. Vlachos ◽  
Suresh V. Garimella
Keyword(s):  
Flow Field ◽  
Heat Source ◽  
Liquid Flow ◽  
Heated Surface ◽  
Jet Impingement ◽  
Vapor Flow ◽  
Wall Jet ◽  
Phase Flow ◽  
Two Phase ◽  
Time Resolved

Two-phase liquid-vapor flow field measurements of confined jet impingement with boiling are performed using time-resolved stereo particle image velocimetry (stereo-PIV). A single circular jet of water, impinges normally from a 3.75 mm-diameter orifice onto a submerged circular heat source at an orifice-to-target spacing of 4 jet diameters. The impinging jet outflow including the vapor generated at the heat source are confined between the jet orifice plate and the bottom test section wall. Fluorescent seeding particles (10 μm in diameter) and time-resolved PIV measurements (taken at a sampling rate of 750 Hz) allow for imaging of the instantaneous interactions between the liquid and vapor structures. Liquid-phase velocity vectors within the two-phase flow field (with high vapor fractions) are presented as a function of heat flux at jet Reynolds numbers of 5,000 and 15,000 and contrasted with single-phase flow. The time-resolved measurements are used to highlight the influence of the vapor phase on the liquid flow field. It is found that bubble formation effectively blocks the developing wall-jet flow on the heated surface. The resulting liquid flow field in the confinement gap is dominated by vapor motion rather than by the entrainment from the developing wall jet.

A new Approach to the Fixation of a Metacarpophalangeal Joint Prosthesis

1983 ◽  
Vol 12 (3) ◽  
pp. 135-140 ◽  
Author(s):  
P S Walker ◽  
D Nunamaker ◽  
R Huiskes ◽  
T Parchinski ◽  
D Greene
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bone Ingrowth ◽  
Knee Prosthesis ◽  
Metacarpophalangeal Joint ◽  
Shear Stresses ◽  
Interface Shear ◽  
Element Analysis ◽  
Total Knee ◽  
One Year

A significant problem with rigid prosthetic stems applied in the finger bones, as well as in other bones of the upper and lower extremity, is resorption of bone at the interface. An investigation was carried out using a plastic plug which would more evenly distribute the stresses to the bone, with fine ridges to produce enhanced fixation by bony ingrowth. A total knee prosthesis in the cat was used as the model, radiographic and histological studies being made at up to one year. A finite element analysis identified areas of high interface and material stresses. With a finely grooved plug, bone ingrowth occurred in all regions except for the region near the bone entry, where the finite element analysis showed the highest interface shear stresses and bone material stresses to occur.

Finite Element Analysis of the Fiber Twist Test

1994 ◽  
Vol 365 ◽  
Author(s):  
F. Gaudette ◽  
T. Ertürk ◽  
S. Robertson
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Fiber Composite ◽  
Elastic Half Space ◽  
Decay Rates ◽  
Shear Stresses ◽  
Interface Shear ◽  
Element Analysis ◽  
Finite Element Program ◽  
Torsional Shear

ABSTRACTInterface and torsional shear stresses in the fiber twist test (FTT) were computed using the ABAQUS finite element program. Interface stress singularities were compared with an elasticity solution for the torsion of a fiber embedded in an elastic half space [1]. Single fiber composite systems having perfectly bonded interfaces and fiber/matrix shear modulus ratios of Gf /Gm = 1 – 3 were considered. The decay rates and depths of the interface shear stress σrθ and the torsional shear stress σZθ in the fiber and matrix were evaluated for each Gf/Gm ratio.

Control of Adiabatic Liquid/Vapor Flow Utilizing EHD Conduction Pumping Mechanism

2004 ◽  
Author(s):  
Yinshan Feng ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Mass Flux ◽  
Two Phase Flow ◽  
Finite Thickness ◽  
Flow Distribution ◽  
Vapor Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Phase Liquid ◽  
Liquid Vapor

Unlike the electrohydrodynamic (EHD) induction and iondrag pumping, the conduction pumping is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes which are based on the process of dissociation of the neutral electrolytic species and recombination of the generated ions. The conduction term here represents a mechanism for electric current flow in which charged carriers are produced not by injection from electrodes, but by dissociation of molecules within the fluid. This paper presents the control of adiabatic two-phase (liquid/vapor) flow distribution with EHD conduction pumping mechanism at two mass flux levels, Gtotal = 50 kg/m2s and Gtotal = 100 kg/m2s. The effects of the vapor quality, ranging from 0 to 26%, on the EHD conduction pumping have also been experimentally investigated. The measured pressure data show that the EHD conduction pumping can significantly decrease the pressure drop of the two-phase flow. It is also found that the performances of the EHD conduction pump are related to the mass flux and quality of two-phase flow.

Sign in / Sign up

Export Citation Format

Share Document