Investigation on Flow Patterns and Transition Characteristics in a Tube-Bundle Channel

2009 ◽  
Author(s):  
Guangyao Lu ◽  
Guisheng Zhao ◽  
Junsheng Ren ◽  
Wenyuan Xiang ◽  
Huaning Ai
Keyword(s):  
Flow Pattern ◽  
High Speed ◽  
Tube Bundle ◽  
Bubbly Flow ◽  
Flow Patterns ◽  
Vertical Tube ◽  
Two Phase ◽  
Flow Pattern Map ◽  
Boiling Flow ◽  
Churn Flow

Tube-bundle channels have been widely used in condenser-evaporator and other industrial heat-exchange equipments. The characteristics of two-phase flow patterns and their transitions for refrigerant R-113 through a vertical tube-bundle channel are experimentally investigated using high-speed camera. Experiments show that there are four main flow patterns in the tube-bundle channel, which are bubbly flow, bubbly-churn flow, churn flow and annular flow. And in the same cross-section of tube-bundle channels, it is shown that there might be different flow patterns in different sub-channels. The flow pattern transitions exhibit unsynchronized in different sub-channels. On the basis of experimental research, the flow pattern map is drawn and analyses are made on the comparison of differences between boiling flow patterns in circular tubes and those in tube-bundle channels.

Experimental Investigation of Air-Water Two Phase Flow Regime in Vertical Mini Pipe

2010 ◽  
Author(s):  
Pedram Hanafizadeh ◽  
Soheil Ghanbarzadeh ◽  
Arash Nouri Gheimasi ◽  
Mohammad Hassan Saidi
Keyword(s):  
Flow Pattern ◽  
Water Flow ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Gas Phases ◽  
Flow Pattern Map ◽  
Video Recorder

In this study the flow patterns of air-water two phase flows have been investigated experimentally in a vertical mini pipe. The flow regimes observed by 1200 fps high speed video recorder in the pipe with diameters of 2, 3 and 4 mm having the length of 27, 31 and 25cm, respectively. The comprehensive visualization of air water two phase flow in a vertical mini pipe has been performed to realize the physics of such two phase flow. Different flow patterns of air–water flow were observed simultaneously in the mini pipe at different values of air and water flow rates. Consequently the flow pattern map proposed for flow in mini-pipe in terms of superficial velocities of liquid and gas phases. The resulted flow pattern map is compared with those of other researchers in the existing literatures.

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 Boiling Visualization of R-134a in a Vertical Channel of Small Diameter

2007 ◽  
Author(s):  
Claudi Marti´n-Callizo ◽  
Bjo¨rn Palm ◽  
Wahib Owhaib ◽  
Rashid Ali
Keyword(s):  
Flow Pattern ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
R 134A ◽  
Heated Length

The present work reports on flow boiling visualization of refrigerant R-134a in a vertical circular channel with internal diameter of 1.33 mm and 235 mm in heated length. Quartz tube with a homogeneous ITO-coating is used allowing heating and simultaneous visualization. Flow patterns have been observed along the heated length with the aid of a digital camera with close-up lenses. From the flow boiling visualization, seven distinct two-phase flow patterns have been observed: Isolated bubbly flow, confined bubbly flow, slug flow, churn flow, slug-annular flow, annular flow, and mist flow. Two-phase flow pattern observations are presented in the form of flow pattern maps. Finally, the experimental flow pattern map is compared to models developed for conventional sizes as well as to a microscale map for air-water mixtures available in the literature, showing a large discrepancy.

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.

Flow Boiling Visualization of R-134a in a Vertical Channel of Small Diameter

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Claudi Martín-Callizo ◽  
Björn Palm ◽  
Wahib Owhaib ◽  
Rashid Ali
Keyword(s):  
Flow Pattern ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
R 134A ◽  
Heated Length

The present work reports on flow boiling visualization of refrigerant R-134a in a vertical circular channel with an internal diameter of 1.33 mm and 235 mm in heated length. A quartz tube with a homogeneous Indium Tin Oxide coating is used to allow heating and simultaneous visualization. Flow patterns have been observed along the heated length with the aid of high-speed complementary metal oxide semiconductor (CMOS) digital camera. From the flow boiling visualization, seven distinct two-phase flow patterns have been observed: isolated bubbly flow, confined bubbly flow, slug flow, churn flow, slug-annular flow, annular flow, and mist flow. Two-phase flow pattern observations are presented in the form of flow pattern maps. The effects of the saturation temperature and the inlet subcooling degree on the two-phase flow pattern transitions are elucidated. Finally, the experimental flow pattern map is compared with models developed for conventional sizes as well as to a microscale map for air-water mixtures available in literature, showing a large discrepancy.

Two-Phase Flow Patterns in a Four by Four Rod Bundle

2006 ◽  
Author(s):  
Yoshitaka Mizutani ◽  
Shigeo Hosokawa ◽  
Akio Tomiyama
Keyword(s):  
Flow Pattern ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Square Lattice ◽  
Phase Flow ◽  
Two Phase ◽  
Local Flow ◽  
Rod Bundle ◽  
Four Square

Air-water two-phase flow patterns in a four by four square lattice rod bundle consisting of an acrylic channel box of 68 mm in width and transparent rods of 12 mm in diameter were observed by utilizing a high speed video camera, FEP (fluorinated ethylene propylene) tubes for rods, and a fiberscope inserted in a rod. The FEP possesses the same refractive index as water, and thereby, whole flow patterns in the bundle and local flow patterns in subchannels were successfully visualized with little optical distortion. The ranges of liquid and gas volume fluxes, <JG> and <JL>, in the present experiments were 0.1 < <JL> < 2.0 m/s and 0.04 < <JG> < 8.85 m/s, which covered typical two-phase flow patterns appearing in a fuel bundle of a boiling water nuclear reactor. As a result, the following conclusions were obtained: (1) the region of slug flow in the <JG> – <JL> flow pattern diagram is so narrow that it can be regarded as a boundary between bubbly and churn flows, (2) the boundary between bubbly and churn flows is close to the boundary between bubbly and slug flows of the Mishima & Ishii’s flow pattern transition model, and (3) the boundary between churn and annular flows is well predicted by the Mishima & Ishii’s model.

Micro-Scale Flow Pattern Classification Based on the K-Means Clustering Algorithm

2010 ◽  
Author(s):  
Daniel Sempe´rtegui ◽  
Gherhardt Ribastki
Keyword(s):  
Flow Pattern ◽  
High Speed ◽  
Clustering Algorithm ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Flow Patterns ◽  
Statistical Characteristics ◽  
Phase Flow ◽  
Two Phase

In the present work, an objective method to characterize two-phase flow pattern was developed and implemented. The method is based on the characteristics of the signals provided by transducers measuring local temperature and pressure plus the intensity of a laser beam crossing the two-phase flow. The statistical characteristics of these signals were used as input features for the k-means clustering method. In order to implement the method, experimental flow patterns were obtained during flow boiling of R245fa in a 2.32 mm ID tube. Experiments were performed for mass velocities from 100 to 700kg/m2s, saturation temperature of 31 °C and vapor qualities up to 0.99. The cluster classification was compared against flow patterns segregated based on high speed camera images (8000 images/s) and a reasonable agreement was obtained.

Flow Patterns of Oil/Water Two-Phase Upflows in a Small Vertical Tube

2011 ◽  
Vol 396-398 ◽  
pp. 274-278
Author(s):  
Zhen Ying Zhao ◽  
Jia Hao Wang ◽  
Hai Yan Min ◽  
Li Min Yang ◽  
Ji He Yang
Keyword(s):  
High Speed ◽  
Theoretical Models ◽  
Flow Patterns ◽  
Vertical Tube ◽  
Stainless Steel Tube ◽  
Internal Diameter ◽  
Two Phase ◽  
Experimental Conditions ◽  
Transparent Plastic ◽  
Oil Water

The flow patterns of oil/water two-phase upward flows in a small vertical tube with an internal diameter of 0.010 m were investigated by high speed video system. Using stainless steel tube as test section, transparent plastic tube as observing section and deionized water and kerosene (density of 796kg/m3) as working fluids, 5 flow patterns, i.e., annular, churn, slug, bubble and dispersed droplets, were observed under the experimental conditions. The transition boundaries of these flow patterns were compared with the literature and theoretical models of Taitel et al [1] for gas-liquid upward flows. There are some differences of the transition boundaries between the present study and the literature of either gas-liquid or liquid-liquid systems. The theoretical models of Taitel et al can well predict the transition boundaries from annular to churn and from churn to bubble.

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.

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