Flow Distribution Control Between Two Parallel Meso-Scale Evaporators With Electrohydrodynamic Conduction Pumping

2016 ◽  
Author(s):  
Lei Yang ◽  
Michal Talmor ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Two Phase Flow ◽  
Finite Thickness ◽  
Flow Distribution ◽  
Control Technique ◽  
Working Fluid ◽  
Phase System ◽  
Phase Flow ◽  
Two Phase ◽  
Macro Scale ◽  
Meso Scale

Electrohydrodynamic (EHD) conduction pumps generate pressure to drive dielectric liquids via the electrical Coulomb force exerted within heterocharge layers of finite thickness in the vicinity of the electrodes. By applying an external electric field in a dielectric liquid, the heterocharge layers form due to the net charges as a result of the process of enhanced dissociation of neutral molecules versus the recombination of the generated ions. EHD conduction pumping can be applied to enhance and control mass and heat transfer of both isothermal and nonisothermal liquid and two-phase fluid, with many advantages such as simple design, no moving parts and low power consumption. It also shows its potential as an active control technique for flow distribution for multi-scale systems in both terrestrial and microgravity environment. Flow distribution control based on EHD conduction pumping mechanism was previously investigated in macro-scale. This study experimentally examines its capability in controlling two-phase flow distribution between two parallel meso-scale evaporators. The working fluid was refrigerant HCFC-123. It has been found that an EHD conduction pump could effectively control the two-phase flow distribution via adjusting the flow rate in each branch line, and facilitate the recovery from dry-out condition in two-phase system.

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.

scholarly journals Variational formulation of stationary two-phase flow distribution

2021 ◽  
pp. 101082
Author(s):  
Niccolo Giannetti ◽  
Mark A.B. Redo ◽  
Kiyoshi Saito ◽  
Hiroaki Yoshimura
Keyword(s):  
Variational Formulation ◽  
Two Phase Flow ◽  
Flow Distribution ◽  
Phase Flow ◽  
Two Phase

Two-phase flow distribution in 2D trickle-bed reactors

1999 ◽  
Vol 54 (13-14) ◽  
pp. 2409-2419 ◽  
Author(s):  
Y. Jiang ◽  
M.R. Khadilkar ◽  
M.H. Al-Dahhan ◽  
M.P. Dudukovic
Keyword(s):  
Two Phase Flow ◽  
Flow Distribution ◽  
Phase Flow ◽  
Two Phase ◽  
Trickle Bed Reactors ◽  
Trickle Bed

Modeling Two-Phase Flow in Porous Media Including Fluid-Fluid Interfacial Area

2008 ◽  
Author(s):  
Jennifer Niessner ◽  
S. Majid Hassanizadeh ◽  
Dustin Crandall
Keyword(s):  
Porous Media ◽  
Capillary Pressure ◽  
Two Phase Flow ◽  
Interfacial Area ◽  
Flow In Porous Media ◽  
Extended Model ◽  
Phase Flow ◽  
Two Phase ◽  
Specific Interfacial Area ◽  
Macro Scale

We present a new numerical model for macro-scale two-phase flow in porous media which is based on a physically consistent theory of multi-phase flow. The standard approach for modeling the flow of two fluid phases in a porous medium consists of a continuity equation for each phase, an extended form of Darcy’s law as well as constitutive relationships for relative permeability and capillary pressure. This approach is known to have a number of important shortcomings and, in particular, it does not account for the presence and role of fluid–fluid interfaces. An alternative is to use an extended model which is founded on thermodynamic principles and is physically consistent. In addition to the standard equations, the model uses a balance equation for specific interfacial area. The constitutive relationship for capillary pressure involves not only saturation, but also specific interfacial area. We show how parameters can be obtained for the alternative model using experimental data from a new kind of flow cell and present results of a numerical modeling study.

Micro/Meso Scale Modelling of Two-Phase Flow on Functional Surfaces: A Numerical Simulation of Water Droplets on Natural Hydrophobic Surfaces With Micro Roughness

2009 ◽  
Author(s):  
Y. Y. Yan
Keyword(s):  
Two Phase Flow ◽  
Contact Angles ◽  
Phase Flow ◽  
Fluid Interface ◽  
Water Droplets ◽  
Hydrophobic Surfaces ◽  
Two Phase ◽  
Partial Wetting ◽  
Scale Modelling ◽  
Meso Scale

A micro/meso scale modelling of two-phase droplets move on hydrophilic/hydrophobic surfaces with micro roughness is reported. The physical model is basically of two-phase flow interacting with the surfaces of different hydrophobicity or wettability. Numerical modelling based on the lattice Boltzmann method (LBM) is developed and applied to the computational calculation and simulation. The LBM modelling deals with surface tension dominated behaviour of water droplets in air spreading on a hydrophilic surface with hydrophobic strips of different sizes and contact angles under different physical and interfacial conditions, and aims to find quantitative data and physical conditions of the biomimetic approaches. The current LBM can be applied to simulate two-phase fluids with large density ratio (up to 1000), and meanwhile deal with interactions between a fluid-fluid interface and a partial wetting wall. In the simulation, the interactions between the fluid-fluid interface and the partial wetting wall with different hydrophobic strips such as single strip, intersecting stripes, and alternating & parallel stripes, of different sizes and contact angles are considered and tested numerically; the phenomena of droplets spreading and breaking up, and the effect of hydrophobic strips on the surface wettability or self-cleaning characteristics are simulated, reported and discussed.

Experimental Characterization of Oil-Refrigerant Two-Phase Flow

2000 ◽  
Author(s):  
V. T. Lacerda ◽  
A. T. Prata ◽  
F. Fagotti
Keyword(s):  
Flow Visualization ◽  
Two Phase Flow ◽  
Working Fluid ◽  
Phase Flow ◽  
Oil Viscosity ◽  
Two Phase ◽  
Mixture Flow ◽  
Horizontal Tubes ◽  
Constant Diameter ◽  
Oil Flow

Abstract Several phenomena occurring inside refrigerating systems depend on the interaction between the refrigeration oil and the refrigerant working fluid. Regarding the refrigeration cycle, good miscibility of oil and refrigerant assure easy return of circulating oil to the compressor through the reduction of the oil viscosity. Inside the compressor the lubricant is mainly used for leakage sealing, cooling of hot elements and lubrication of sliding parts. In the compressor bearing systems the presence of refrigerant dissolved in the oil greatly influences the performance and reliability of the compressor due to the outgassing experienced by sudden changes in temperature and pressure resulting in a two-phase mixture with density and viscosity strongly affecting the lubricant characteristics. A general understanding of the oil-refrigerant mixture flow is crucial in developing lubrication models to be used in analysis and simulation of fluid mechanics problems inside the compressor. In the present investigation the refrigeration oil flow with refrigerant outgassing is explored experimentally. A mixture of oil saturated with refrigerant is forced to flow in two straight horizontal tubes of constant diameter. One tube is used for flow visualization and the other is instrumented for pressure and temperature measurements. At the tubes inlet liquid state prevails and as flow proceeds the pressure drop reduces the gas solubility in the oil and outgassing occurs. Initially small bubbles are observed and eventually the bubble population reaches a stage where foaming flow is observed. The flow visualization allowed identification of the two-phase flow regimes experienced by the mixture. Pressure and temperature distributions are measured along the flow and from that mixture quality and void fraction were estimated.

Two-Phase Flow Characteristics in a Co-Flow Induced Microchannel With Microbubbles Generation

2007 ◽  
Author(s):  
Sujin Yeom ◽  
Seung S. Lee ◽  
Sang Yong Lee
Keyword(s):  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Gas Pressure ◽  
Superficial Velocity ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Gas Channel ◽  
Micro Bubble

This paper presents a micro-fluidic device which generates micro-bubbles, ranging from 70μm to 160μm in diameter, and two-phase flow characteristics in the device were tested. The device is composed of three sub-channels: a centered gas channel (10μm×50μm) and two liquid channels (both with 85μm×50μm) on each side of the gas channel. Micro-bubbles are generated by co-flow of gas and liquid at the exit of the gas channel when the drag force becomes larger than the surface tension force as bubbles grow. Methanol and a gas mixture of CO2 and N2 were used as the working fluid. Since the flow rate of gas was very small, the gas momentum effect was considered negligible. Thus, in the present case, the controlling parameters were the liquid superficial velocity and the inlet pressure of the gas. A high speed camera was used to record two-phase flow patterns and micro-bubbles of the device. To confine the ranges of the micro-bubbles generation, two-phase flow patterns in the device is observed at first. Four different flow patterns were observed: annular, annular-slug, slug, and bubbly flow. In bubbly flows, uniform-sized micro-bubbles were generated, and the operating ranges of the liquid superficial velocity and the gas pressure were below 0.132 m/s and 0.7 bar, respectively. Diameters of the micro-bubbles appeared smaller with the higher superficial liquid velocity and/or with a lower gas pressure. Experimental results showed that, with the gas pressure lower than a certain level, the sizes of micro-bubbles were almost insensitive to the gas pressure. In such a ranges, the micro-bubble diameters could be estimated from a drag coefficient correlation, CDw = 31330/Re3, which is different from the correlations for macro-channels due to a larger wall effect with the micro-channels. In the latter part of the paper, as a potential of application of the micro-bubble generator to gas analysis, dissolution behavior of the gas components into the liquid flow was examined. The result shows that the micro-bubble generator can be adopted as a component of miniaturized gas analyzers if a proper improvement could be made in controlling the bubble sizes effectively.

scholarly journals Two-Phase Flow Distribution in Multipass Tube.

1994 ◽  
Vol 60 (580) ◽  
pp. 4145-4150 ◽  
Author(s):  
Manabu Watanabe ◽  
Masafumi Katsuta ◽  
Katsuya Nagata ◽  
Kiyoshi Sakuma
Keyword(s):  
Two Phase Flow ◽  
Flow Distribution ◽  
Phase Flow ◽  
Two Phase
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