Simulation on Flow Pattern Transition With Liquid Nitrogen and its Vapor Using a Droplet Entrainment Model

2020 ◽  
Author(s):  
Rui Zhou ◽  
Tao Xia ◽  
Xiaobin Zhang
Keyword(s):  
Flow Pattern ◽  
Liquid Nitrogen ◽  
Slug Flow ◽  
Flow Patterns ◽  
Eulerian Model ◽  
Ansys Fluent ◽  
Droplet Entrainment ◽  
Flow Pattern Transition ◽  
Churn Flow ◽  
Two Fluid

Abstract A droplet entrainment model was applied to characterize the flow pattern transition in the countercurrent horizontal flow with liquid nitrogen (LN2) and vapor nitrogen (VN2). A two-fluid three-field model consisting of liquid film, gas, and droplet was implemented based on the Eulerian-Eulerian model in ANSYS Fluent®. In the droplet entrainment model, the condition and position of the droplet generation were realized by calculating the velocity gradient in the normal direction of the interface towards the gas core. The droplet entrainment and deposition rates were also included and validated according to the available data of water/air in the literature. Three flow patterns, including stratified-wavy flow, churn flow, and pseudo-slug flow, were identified in simulation results with LN2/VN2. Furthermore, ligament breakup was found to be the main droplet entrainment mechanism in the churn and pseudo-slug flow, and there can be a high probability of the occurrence of bubble burst as well. Compared with water/air, the droplets are more easily to be entrained in LN2/VN2 due to the smaller viscosity and surface tension according to the results of droplet mass flow rate. Pressure drop signals of the three flow patterns were also obtained and analyzed.

An Experimental Study on Air-Water Two-Phase Flow Patterns in Pebble Beds

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Bai Bofeng ◽  
Liu Maolong ◽  
Su Wang ◽  
Zhang Xiaojie
Keyword(s):  
Experimental Study ◽  
Flow Pattern ◽  
Test Section ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pattern Transition

An experimental study was conducted on the air-water two-phase flow patterns in the bed of rectangular cross sections containing spheres of regular distribution. Three kinds of glass spheres with different diameters (3 mm, 6 mm, and 8 mm) were used for the establishment of the test section. By means of visual observations of the two-phase flow through the test section, it was discovered that five different flow patterns occurred within the experimental parameter ranges, namely, bubbly flow, bubbly-slug flow, slug flow, slug-annular flow, and annular flow. A correlation for the bubble and slug diameter in the packed beds was proposed, which was an extended expression of the Tung/Dhir model, Jamialahmadi’s model, and Schmidt’s model. Three correlations were proposed to calculate the void friction of the flow pattern transition in bubble flow, slug flow, and annular flow based on the bubble model in the pore region. The experimental result showed that the modified Tung and Dhir model of the flow pattern transition was in better agreement with the experimental data compared with Tung and Dhir’s model.

Flow Pattern Transition Criteria for Upward Two-Phase Flow in Annulus

2020 ◽  
Author(s):  
He Wen ◽  
Zhao Chenru ◽  
Bo Hanliang
Keyword(s):  
Flow Pattern ◽  
Flow Patterns ◽  
Flow Transition ◽  
Two Phase ◽  
Transition Mechanism ◽  
Flow Pattern Transition ◽  
Transition Criteria ◽  
Asymmetric Shape ◽  
Basic Characteristics ◽  
Churn Flow

Abstract Vertical upward two-phase flows in annulus are of great importance in many industrial fields due to the closely relationship between the flow patterns and the heat transfer characteristics. Common flow patterns in annulus are bubbly (B), slug (S), churn (C) and annular (A) flow, most of which are quite similar to those in tubes. However, due to the elliptic nose and asymmetric shape of the Taylor bubble in annulus, the slug to churn flow transition could be influenced by the channel geometry which was usually ignored in most of the previous researches. The flow pattern transition criteria for tubes are thus not applicable for annulus, especially for slug to churn flow transition, which should be separately studied. Therefore, in this paper, the basic characteristics of the flow pattern in annulus and their transition mechanism are analyzed. In addition, a set of semi-empirical transition criteria with higher accuracy are assessed and selected for annulus based on theoretical analysis and comparisons with experimental data.

Simulation on Flow Pattern Transition With Liquid Nitrogen and Its Vapor Using a Droplet Entrainment Model

2021 ◽  
Author(s):  
Rui Zhou ◽  
Tao Xia ◽  
Xiaobin Zhang
Keyword(s):  
Flow Pattern ◽  
Liquid Nitrogen ◽  
Droplet Entrainment ◽  
Flow Pattern Transition

scholarly journals Flow Pattern Map of Flow Boiling in a Rectangular Channel Filled with Porous Media

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2440
Author(s):  
Youngwoo Kim ◽  
Dae Yeon Kim ◽  
Kyung Chun Kim
Keyword(s):  
Porous Media ◽  
Flow Pattern ◽  
Flow Regime ◽  
Annular Flow ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Flow Patterns ◽  
Flow Pattern Map ◽  
Mist Flow ◽  
Churn Flow

A flow visualization study was carried out for flow boiling in a rectangular channel filled with and without metallic random porous media. Four main flow patterns are observed as intermittent slug-churn flow, churn-annular flow, annular-mist flow, and mist flow regimes. These flow patterns are clearly classified based on the high-speed images of the channel flow. The results of the flow pattern map according to the mass flow rate were presented using saturation temperatures and the materials of porous media as variables. As the saturation temperatures increased, the annular-mist flow regime occupied a larger area than the lower saturation temperatures condition. Therefore, the churn flow regime is narrower, and the slug flow more quickly turns to annular flow with the increasing vapor quality. The pattern map is not significantly affected by the materials of porous media.

Flow-Pattern Transition and Hydrodynamic Modeling of Churn Flow

SPE Journal ◽  
1999 ◽  
Vol 4 (12) ◽  
Author(s):  
J. Tengesdal ◽  
A.S. Kaya ◽  
Cem Sarica
Keyword(s):  
Flow Pattern ◽  
Hydrodynamic Modeling ◽  
Flow Pattern Transition ◽  
Churn Flow

Detecting the Flow Pattern Transition in the Gas-Liquid Two-Phase Flow Using Multivariate Multi-Scale Entropy Analysis

2019 ◽  
Vol 74 (10) ◽  
pp. 837-848 ◽  
Author(s):  
Yudong Liu ◽  
Dayang Wang ◽  
Yingyu Ren ◽  
Ningde Jin
Keyword(s):  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Mean Value ◽  
Entropy Rate ◽  
Permutation Entropy ◽  
Phase Flow ◽  
Two Phase ◽  
Multi Scale ◽  
Flow Pattern Transition

AbstractDue to the complex flow structure and non-uniform phase distribution in the vertical upward gas-liquid two-phase flow, an eight-electrode rotating electric field conductance sensor is used to obtain multi-channel conductance signals. The flow patterns of the vertical upward gas-liquid two-phase flow are classified according to the images obtained from a high-speed camera. Then, we employ the multivariate weighted multi-scale permutation entropy (MWMPE) to detect the instability of flow pattern transition in the gas-liquid two-phase flow. Afterwards, we compare the results of the MWMPE with those of the single-channel weighted multi-scale permutation entropy (SCWMPE) and multivariate multi-scale sample entropy (MMSE). The comparison results indicate that, compared with the SCWMPE and MMSE, the MWMPE has superior performance in terms of the high-resolution presentation of flow instability in the gas-liquid two-phase flow. Finally, we extract the mean value of the MWMPE in whole scales and the entropy rate of the MWMPE in the small scales. The results indicate that the normalized mean value and normalized entropy rate of MWMPE are very sensitive to the transitions of flow patterns, thus allowing the detection of the instability of flow pattern transition.

Unified Model for Gas-Liquid Pipe Flow Via Slug Dynamics: Part 1 — Model Development

2002 ◽  
Author(s):  
Hong-Quan Zhang ◽  
Qian Wang ◽  
Cem Sarica ◽  
James P. Brill
Keyword(s):  
Flow Pattern ◽  
Pipe Flow ◽  
Slug Flow ◽  
Control Volume ◽  
Model Development ◽  
Flow Patterns ◽  
Hydrodynamic Characteristics ◽  
Momentum Exchange ◽  
Two Phase ◽  
Inclination Angles

A unified hydrodynamic model is developed for predictions of flow pattern transitions, pressure gradient, liquid holdup and slug characteristics in gas-liquid pipe flow at different inclination angles from −90 to 90 deg. The model is based on the dynamics of slug flow, which shares transition boundaries with all the other flow patterns. By use of the entire film zone as the control volume, the momentum exchange between the slug body and the film zone is introduced into the momentum equations for slug flow. The equations of slug flow are used not only to calculate the slug characteristics, but also to predict transitions from slug flow to other flow patterns. Significant effort has been made to eliminate discontinuities among the closure relationships through careful selection and generalization. The flow pattern classification is also simplified according to the hydrodynamic characteristics of two-phase flow.

The bubble-slug flow pattern transition and instabilities of void fraction waves

1987 ◽  
Vol 13 (2) ◽  
pp. 199-217 ◽  
Author(s):  
A. Matuszkiewicz ◽  
J.C. Flamand ◽  
J.A. Bouré
Keyword(s):  
Flow Pattern ◽  
Void Fraction ◽  
Slug Flow ◽  
Flow Pattern Transition

Flow Boiling Patterns of Liquid Nitrogen in Micro-Tubes

2008 ◽  
Author(s):  
P. Zhang ◽  
X. Fu ◽  
R. Z. Wang
Keyword(s):  
Liquid Nitrogen ◽  
High Speed ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
Superconducting Devices ◽  
Surface Tension Force ◽  
Flow Patterns ◽  
Factors Affecting ◽  
Major Factors ◽  
Churn Flow

Application of liquid nitrogen to cooling is widely used in such fields as cooling of the high temperature superconducting devices, cryosurgery and so on. In order to have a full understanding of the flow and heat transfer characteristics of liquid nitrogen in micro-tube, high-speed digital photography was employed to acquire the typical flow boiling patterns of liquid nitrogen in micro-tubes in the experiments. The main flow patterns were bubbly flow, slug flow, churn flow and annular flow. And the confined bubbly flow and mist flow were also observed. These flow patterns were characterized on the flow regime maps. And the surface tension force and the size of the tube diameter were found to be the major factors affecting the flow pattern transitions.

Surfactant Use for Slug Flow Pattern Suppression in a Horizontal Pipe

2003 ◽  
Author(s):  
R. J. Wilkens ◽  
S. R. Glassmeyer ◽  
G. J. Rosebrock ◽  
K. M. Storage ◽  
T. M. Storage
Keyword(s):  
Flow Pattern ◽  
Liquid Flow ◽  
Pipe Flow ◽  
Slug Flow ◽  
Flow Patterns ◽  
Flow Transition ◽  
Horizontal Pipe ◽  
Surfactant Additive ◽  
Gas Liquid Flow

A set of experiments was performed to study flow pattern suppression in gas-liquid pipe flow by means of surfactant additive. Results suggest that addition of the surfactant to gas-liquid flow significantly reduces the occurrence of slug flow. In addition, previously unreported flow patterns were observed to exist between slug and dispersed bubble flows. It is concluded that new mechanisms for slug flow transition need to be considered.

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