The flow patterning capability of localized natural convection

2016 ◽  
Vol 18 (36) ◽  
pp. 25380-25387 ◽  
Author(s):  
Ling-Ting Huang ◽  
Ling Chao
Keyword(s):  
Natural Convection ◽  
Flow Pattern ◽  
State Diagram ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Heat Sources

Controlling flow patterns to align materials can have various applications in optics, electronics, and biosciences. We developed a natural-convection-based method to create desirable spatial flow patterns by controlling the locations of heat sources and proposed a flow pattern state diagram which suggests a suitable range of operating conditions for flow patterning.

Experimental Investigation on Flow Patterns of Cylindrical-Conical Spout-Fluidizing Bed

2011 ◽  
Vol 354-355 ◽  
pp. 338-343
Author(s):  
Qian Jun Li ◽  
Dong Ping Zhang
Keyword(s):  
Flow Pattern ◽  
Fluidized Bed ◽  
Fixed Bed ◽  
Ccd Camera ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Hydrodynamic Characteristics ◽  
Experimental Investigations ◽  
Bed Height ◽  
Bed Materials

Experimental investigations on hydrodynamic characteristics of cylindrical pressurized spout-fluidizing bed were carried out. Two kinds of millet were used as bed materials. The operational pressure is 0.1MPa~0.4MPa (absolutely pressure). Five distinct flow patterns, i.e, fixed bed(FB), jet in fluidized bed with bubbles(JFB), jet in fluidized bed with slugging(JFS), spout with aeration(SA) and spout-fluidizing bed(SF) were identified. Effects of the static bed height and operational pressure on the flow pattern map were particularly studied. Typical flow pattern images obtained by a high- resolution digital CCD camera were presented for classifying these flow patterns. Typical flow pattern maps were plotted for describing the transitions between flow patterns with operating conditions

Natural Convection Flows in Parallel-Channel Systems

1963 ◽  
Vol 85 (4) ◽  
pp. 339-345 ◽  
Author(s):  
J. C. Chato
Keyword(s):  
Natural Convection ◽  
Flow Pattern ◽  
Heat Input ◽  
Natural Circulation ◽  
Flow Patterns ◽  
Parallel Channel ◽  
Multiple Channel ◽  
Channel Configuration ◽  
Channel Systems

An analysis was developed for natural circulation flows in vertical multiple-channel systems with nonuniform heat inputs. A three-channel configuration was investigated in detail both analytically and experimentally. The results showed the existence of a metastable regime in which two metastable flow patterns could occur for a given set of heat input rates. A third predicted flow pattern in this regime was shown to be unstable and, therefore, nonexistent in practice.

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.

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2003 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase ◽  
Micro Channels

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406 × 2.032 mm cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal that the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Annual flow is identified as the dominant flow pattern for conditions relevant to two-phase micro-channel heat sinks, and forms the basis for development of a theoretical model for both pressure drop and heat transfer in micro-channels. Features unique to two-phase micro-channel flow, such as laminar liquid and gas flows, smooth liquid-gas interface, and strong entrainment and deposition effects are incorporated into the model. The model shows good agreement with experimental data for water-cooled heat sinks.

scholarly journals Footprints of a flapping wing

2017 ◽  
Vol 818 ◽  
pp. 1-4 ◽  
Author(s):  
Jun Zhang
Keyword(s):  
Flow Pattern ◽  
External Force ◽  
Thrust Force ◽  
Flow Patterns ◽  
Flapping Wing ◽  
Flapping Wings ◽  
Left Behind ◽  
Full Picture

Birds have to flap their wings to generate the needed thrust force, which powers them through the air. But how exactly do flapping wings create such force, and at what amplitude and frequency should they operate? These questions have been asked by many researchers. It turns out that much of the secret is hidden in the wake left behind the flapping wing. Exemplified by the study of Andersen et al. (J. Fluid Mech., vol. 812, 2017, R4), close examination of the flow pattern behind a flapping wing will inform us whether the wing is towed by an external force or able to generate a net thrust force by itself. Such studies are much like looking at the footprints of terrestrial animals as we infer their size and weight, figuring out their walking and running gaits. A map that displays the collection of flow patterns after a flapping wing, using flapping frequency and amplitude as the coordinates, offers a full picture of its flying ‘gaits’.

Natural Convection From Protruding Heat Sources in a Channel

2003 ◽  
Author(s):  
Tunc Icoz ◽  
Qinghua Wang ◽  
Yogesh Jaluria
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Rayleigh Scattering ◽  
Convection Heat Transfer ◽  
Separation Distance ◽  
Natural Convection Heat Transfer ◽  
Temperature Profiles ◽  
Heat Sources ◽  
Convection Heat

Natural convection has important implications in many applications like cooling of electronic equipment due to its low cost and easy maintenance. In the present study, two-dimensional natural convection heat transfer to air from multiple identical protruding heat sources, which simulate electronic components, located in a horizontal channel has been studied numerically. The fluid flow and temperature profiles, above the heating elements placed between an adiabatic lower plate and an isothermal upper plate, are obtained using numerical simulation. The effects of source temperatures, channel dimensions, openings, boundary conditions, and source locations on the heat transfer from and flow above the protruding sources are investigated. Different configurations of channel dimensions and separation distances of heat sources are considered and their effects on natural convection heat transfer characteristics are studied. The results show that the channel dimensions have a significant effect on fluid flow. However, their effects on heat transfer are found to be small. The separation distance is found to be an important parameter affecting the heat transfer rate. The numerical results of temperature profiles are compared with the experimental measurements performed using Filtered Rayleigh Scattering (FRS) technique in an earlier study, indicating good agreement. It is observed that adiabatic upper plate assumption leads to better temperature predictions than isothermal plate assumption.

scholarly journals Suspended sediment distribution under varied currents in the largest river-connected lake of China

2017 ◽  
Vol 18 (3) ◽  
pp. 994-1004 ◽  
Author(s):  
Hua Wang ◽  
Yijun Zhao ◽  
Fengnian Zhou ◽  
Huaiyu Yan ◽  
Yanqing Deng ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Suspended Sediment ◽  
Flow Patterns ◽  
Field Investigation ◽  
Gravity Flow ◽  
Shear Stresses ◽  
Sediment Distribution ◽  
Back Flow ◽  
The North ◽  
Dry Seasons

Abstract Poyang Lake was selected as the research area. Based on laboratory experiment, field investigation and numerical simulation, the spatial distributions of suspended sediment (SS) under the gravity-flow, jacking-flow and back-flow patterns were quantitatively analysed. An annular flume experiment was conducted to determine the critical starting shear stresses of the sediments in the flood and dry seasons. By numerical experiment, the SS transport under different flow patterns was explored. Several results stand out. (1) The critical starting shear stresses of the sediments in the flood and dry seasons were 0.35 N·m−2 and 0.29 N·m−2, respectively. (2) Due to the strongest flow disturbance and scouring effect, SS under the gravity-flow pattern was characterized by the highest loads. The lowest SS was observed during the jacking-flow pattern, which could be attributed to the lowest water level gap between the lake and external rivers. The loads ranged from 0.053 kg·m−3 to 0.068 kg·m−3. (3) Under the back-flow pattern, SS in the north lake was evidently influenced by the Yangtze River, and the mean value was approximately 0.12 kg·m−3. With the gradually weakened back-flow impact, the SS load was decreased from the north to the middle of the lake.

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