Characteristics of Water Flow in a Vertical Micro Tube

2003 ◽  
Author(s):  
Xiaoping Wang ◽  
Makoto Watanabe ◽  
Masahiro Shoji
Keyword(s):  
High Speed ◽  
Single Phase ◽  
Transient Flow ◽  
Capillary Tube ◽  
Excess Pressure ◽  
Phase Flow ◽  
Two Phase ◽  
Pressurized Water ◽  
Tube Wall Temperature ◽  
Tube Exit

Fluid flow and heat transfer in micro-channel has received attention in developing electronic element cooling systems and in designing thermal elements of micro machines and refrigerators. In the present experiment, pressurized water in the chamber flushed out of a vertical capillary tube of 0.5mm in inner diameter and 1150mm in length. The outer surface of the tube was insulated. The chamber excess pressure was changed from 0.1 MPa to 0.6 MPa and also the inlet water temperature was widely varied. At low excess pressures, the flow is liquid single-phase flow but at high excess pressures, phase change (flushing) takes place inside and/or near the exit end of the tube and the flow becomes two-phase flow of oscillatory or intermittent. Mass flow rate as well as tube wall temperature (distribution and fluctuation) were measured, and the aspect of flushing at the tube exit end was observed using high-speed video movie. It is found that the flow regime can be classified into three (single-phase, two-phase and transient flow regimes) depending on the chamber excess pressure.

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.

An Analytical Model for Prediction of Two-Phase (Noncondensable) Flow Pump Performance

1985 ◽  
Vol 107 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Okitsugu Furuya
Keyword(s):  
Analytical Method ◽  
Single Phase ◽  
Two Phase Flow ◽  
Control Volume ◽  
Model Development ◽  
Oil Well ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Pressurized Water

During operational transients or a hypothetical LOCA (loss of coolant accident) condition, the recirculating coolant of PWR (pressurized water reactor) may flash into steam due to a loss of line pressure. Under such two-phase flow conditions, it is well known that the recirculation pump becomes unable to generate the same head as that of the single-phase flow case. Similar situations also exist in oil well submersible pumps where a fair amount of gas is contained in oil. Based on the one dimensional control volume method, an analytical method has been developed to determine the performance of pumps operating under two-phase flow conditions. The analytical method has incorporated pump geometry, void fraction, flow slippage and flow regime into the basic formula, but neglected the compressibility and condensation effects. During the course of model development, it has been found that the head degradation is mainly caused by higher acceleration on liquid phase and deceleration on gas phase than in the case of single-phase flows. The numerical results for head degradations and torques obtained with the model favorably compared with the air/water two-phase flow test data of Babcock and Wilcox (1/3 scale) and Creare (1/20 scale) pumps.

scholarly journals A study on high speed two-phase flow through a capillary tube.

1985 ◽  
Vol 51 (463) ◽  
pp. 1033-1041 ◽  
Author(s):  
Kunio HIJIKATA ◽  
Yasuo MORI ◽  
Takeo NAGASAKI ◽  
Kunio NOHATA
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Capillary Tube ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through

Computational Simulation of High-Speed Steady Homogeneous Two-Phase Flow in Complex Piping Systems

1982 ◽  
Vol 104 (4) ◽  
pp. 272-277
Author(s):  
D. B. Bliss ◽  
T. R. Quackenbush ◽  
M. E. Teske
Keyword(s):  
High Speed ◽  
Single Phase ◽  
Two Phase Flow ◽  
Computational Simulation ◽  
State Equation ◽  
Phase Flow ◽  
Two Phase ◽  
Subcooled Liquid ◽  
Constant Area ◽  
Piping Systems

A study was undertaken to predict steady flow conditions in two-phase steam/water flows in safety/relief discharge piping systems. The homogeneous-equilibrium model was used for the two-phase flow along with the ASME Steam Tables in subroutine form as a state equation. The approach can also accommodate single-phase flows of superheated steam or subcooled liquid. Subroutines were developed to simulate flows through isentropic area changes, abrupt area changes, adiabatic constant area pipes with friction, valves, two-phase shock waves, and mass addition at pipe junctions. These subroutines were combined to predict conditions in arbitrary complex piping systems. Sample calculations which treat both single line and multiple-branch piping systems are included.

Transient Local Resolution of Flow Boiling in a Microchannel With a Streamlined Pin Fin

2018 ◽  
Author(s):  
Anatoly Parahovnik ◽  
Yingying Wang ◽  
Yoav Peles
Keyword(s):  
High Speed ◽  
Single Phase ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Temperature Measurements ◽  
Phase Flow ◽  
Two Phase ◽  
Pin Fin ◽  
Boiling Process ◽  
Microchannel Device

Flow boiling around a single streamlined pin fin in a microchannel with engineering fluid, HFE-7000, was experimentally studied. A micro heater and an array of resistance temperature detectors (RTDs) were integrated into the microchannel device to enable heating and local temperature measurements on the microchannel internal wall. Thermal behavior as a function of position, heat flux, mass flux, and pressure was investigated for single phase flow and flow boiling. High-speed visualization of the two-phase flow was used to identify pertinent flow patterns and to complement the surface temperature measurements. It was found that the nucleate boiling regime and the periodic behavior of the boiling process was strongly dependent on the system’s pressure.

Two-Phase Flow Simulation of a Non-Boussinesq Density Current

2010 ◽  
Author(s):  
A. M. Mehdizadeh ◽  
M. R. Bazargan-Lari ◽  
A. Mansoori ◽  
A. Mehdizadeh
Keyword(s):  
High Speed ◽  
Single Phase ◽  
Two Phase Flow ◽  
Salt Water ◽  
Flow Simulation ◽  
Boussinesq Approximation ◽  
Density Current ◽  
Phase Flow ◽  
Density Currents ◽  
Two Phase

Boussinesq approximation was widely used in the previous studies to model dilute density or turbidity currents. This approximation was helping to simplify the governing equations and employing a single phase simulation of density currents. In contrast to the general approach of the previous researches who tried to avoid two-phase flow simulation, in this study the two-phase simulation of density current is performed to compare the solution based on the non-Boussinesq behaviour of the fluid with that assuming the Boussinesq approximation. The above goal has been achieved by employing the mixture model for the two-phase flow simulation. The geometry of study is based on a long shallow channel in which a high speed jet of salt-water entering the stilling fresh water via the sluice gate. Different turbulence models results have been compared with the experimental data in order to verify the best results. Also, results of two-phase simulation have been compared to those obtained by the Boussinesq approximation, results show that the two-phase simulation provides superior prediction compared to the conventional single phase flow simulation.

Comparing the Enhancement of Heat Transfer Caused by Sliding Gas Bubbles and by Sliding Vapor Bubbles in Subcooled Flow in a Minichannel

2013 ◽  
Author(s):  
Khaled E. Albahloul ◽  
D. Keith Hollingsworth ◽  
Larry C. Witte ◽  
Arif B. Ozer
Keyword(s):  
Heat Transfer ◽  
Liquid Flow ◽  
High Speed ◽  
Single Phase ◽  
Imaging System ◽  
Bubble Nucleation ◽  
Phase Flow ◽  
Lower Wall ◽  
Vapor Bubbles ◽  
Two Phase

Studies published over the past decade have established the importance of sliding bubbles in enhancing the heat transfer in subcooled two-phase flow in channels small enough to confine the bubbles. Recent work in this laboratory (Ozer et al., 2011, 2012) proposed that the primary enhancement mechanism is a single-phase convective mechanism: the transport of cold fluid nearer the wall due to the mixing behind the bubble. This is in contrast to two phase-change mechanisms: distributed bubble nucleation and the evaporation of the liquid microlayer between a sliding bubble and the surface. The work reported here explores this hypothesis by comparing the heat transfer enhancement produced by injected air bubbles to Ozer’s measurements obtained with naturally nucleated vapor bubbles. Data were collected under similar conditions in a highly subcooled laminar flow of Novec 649 in a horizontal rectangular minichannel of 1.21 to 1.484 mm channel spacing. The channel was formed by an electrically heated metallic upper wall and an unheated transparent lower wall. For the air/liquid flow, bubbles were injected at either a single point on the lower wall or through a sintered metal plug. The latter system produced a more channel-filling distribution of bubbles. A high-speed imaging system recorded the bubble motion and liquid crystal thermography recorded time-averaged surface temperature data. The comparison is presented in the form of the streamwise evolution of surface temperatures and the enhancement in time-averaged Nusselt number. Also, results for the passage of a single air bubble are presented. The air/liquid flow produced a Nu enhancement of between 120–350% compared to a single-phase flow at the same conditions. The passage of the single gas bubble produced a decrease in the wall temperature directly behind the bubble of 2–5 °C. The Nu enhancement produced by the air/liquid data and the nucleated vapor data is well correlated to appropriate dimensionless groups involving bubble diameter and frequency. The results from both data sets support the contention that a transient transport/mixing model developed previously for the vapor/liquid case captures the dominant single-phase convective mechanism in sliding bubble flows in highly confined channels.

Critical Review of Stabilized Nanoparticle Transport in Porous Media

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Xiaoyan Meng ◽  
Daoyong Yang
Keyword(s):  
Porous Media ◽  
Steady State ◽  
Single Phase ◽  
Transient Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Flow Conditions ◽  
Nanoparticle Transport ◽  
Two Phase ◽  
Transport In Porous Media

Over the past few decades, due to the special features (i.e., easily produced, large-surface-area-to-volume ratio, and engineered particles with designed surface properties), nanoparticles have not only attracted great attentions from the oil and gas industry but also had various applications from drilling and completion, reservoir characterization, to enhanced oil recovery (EOR). As sensors or EOR agents, thus, fate and behavior of nanoparticles in porous media are essential and need to be investigated thoroughly. Nevertheless, most of the published review papers focus on particle transport in saturated porous media, and all of them are about steady-state flow conditions. So far, no attempts have been extended to systematically review current knowledge about nanoparticle transport in porous media with single-phase and two-phase flow systems under both steady-state and unsteady-state conditions. Accordingly, this review will discuss nanoparticle transport phenomena in porous media with its focus on the filtration mechanisms, the underlying interaction forces, and factors dominating nanoparticle transport behavior in porous media. Finally, mathematical models used to describe nanoparticle transport in porous media for both single-phase flow and two-phase flow under steady-state and transient flow conditions will be summarized, respectively.

Numerical Study of the Single-Phase and Two-Phase Flow in a Centrifugal Pump

2013 ◽  
Vol 307 ◽  
pp. 215-218
Author(s):  
Te Ba ◽  
Arthur Teck Bin Lim ◽  
Chang Wei Kang
Keyword(s):  
Centrifugal Pump ◽  
Single Phase ◽  
Transient Flow ◽  
Two Phase Flow ◽  
Numerical Study ◽  
Flow Simulation ◽  
Phase Flow ◽  
Two Phase ◽  
Normal Mass ◽  
Phase Water

The paper presents the numerical investigation of a radial flow centrifugal pump with 2D curvature blade geometry. The geometry is based on the experimental equipment by Anagostopulos. Single phase (water) flow is modeled with a normal mass flow rate and rotation speed. Pressure distribution and fluid streamlines are evaluated and visualized. An extension of the model to transient flow and two-phase flow simulation has been done to see the effect of impeller rotation and gas entrainment in the centrifugal operation procedure.

Measurements of single-phase and two-phase flows in a vertical pipe using ultrasonic pulse Doppler method and ultrasonic time-domain cross-correlation method

2013 ◽  
Vol 35 (3) ◽  
Author(s):  
Tat Thang Nguyen ◽  
Hiroshige Kikura ◽  
Ngoc Hai Duong ◽  
Hideki Murakawa ◽  
Nobuyoshi Tsuzuki
Keyword(s):  
Time Domain ◽  
Cross Correlation ◽  
Single Phase ◽  
Ultrasonic Pulse ◽  
Phase Flow ◽  
Beam Diameter ◽  
Vertical Pipe ◽  
Two Phase ◽  
Ultrasonic Time ◽  
Pulse Doppler

Ultrasonic Velocity Profile (UVP) method for measurement of single-phase and two-phase flow in a vertical pipe has recently been developed in the Laboratory for industrial and Environmental Fluid Dynamics, Institute of Mechanics, VAST. The signal processings of the UVP method include the ultrasonic pulse Doppler method (UDM)and the ultrasonic time-domain cross-correlation (UTDC) method. For two-phase flow, simultaneous measurements of both liquid and gas are enabled by using a multi-wave ultrasonic transducer (multi-wave TDX). The multi-wave TDX is able to emit and receive ultrasound of two different center frequencies of 2 MHz and 8 MHz at the same time and position. 2 MHz frequency with beam diameter 10 mm is exploited for measurement of gas. 8 MHz one with beam diameter 3 mm is used for liquid. Measurements have been carried out for laminar and turbulent single-phase flows and bubbly counter-current two-phase flows in two flow loops using two vertical pipes of 26 mm inner diameter (I.D.) and 50 mm I.D. respectively. Based on the measured results, assessment of each method is clarified. Applicability of each method for different conditions of pipe flow has been tested. Suggestions for application of the two methods have been recommended.

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