Aspect Ratio Effect on Adiabatic Two-Phase Flow in Rectangular Microchannels

2009 ◽  
Author(s):  
Chiwoong Choi ◽  
DongIn Yu ◽  
Moohwan Kim
Keyword(s):  
Pressure Drop ◽  
Aspect Ratio ◽  
High Speed ◽  
Two Phase Flow ◽  
Rectangular Cross Section ◽  
Phase Flow ◽  
Long Distance ◽  
Two Phase ◽  
Rectangular Microchannel ◽  
Rectangular Microchannels

Most microscale thermal hydraulic systems have been used rectangular microchannels. In a rectangular microchannel, most important parameter is an aspect ratio. In this study, glass rectangular microchannels were fabricated using MEMS (micro-electro-mechanical system) fabrication techniques with a photosensitive glass. The width of all channels is same to approximately 500 μm and the height of rectangular microchannel was changed. The hydraulic diameters of the rectangular microchannels were 490, 322 and 143 μm. Experiments of adiabatic two-phase flow in the rectangular microchannels were conducted using liquid water and nitrogen gas. Pressure drop was directly measured from embedded pressure ports. And the pressure drop results were compared with correlations. Visualization of flow patterns were achieved with a high-speed camera and a long-distance microscope. Bubble behaviors were analyzed using visualized images based on a unit cell concept. As the aspect ratio decreased, a confinement effect was increased. And the thickness of liquid film in the corner of the rectangular cross section was reduced with the aspect ratio decreased. This result affected all phenomena of two-phase flow in the rectangular microchannels.

Correlations of the Holdup and the Frictional Pressure Drop in Air-Water Two-Phase Flow in a Flat Capillary Rectangular Channel

2004 ◽  
Author(s):  
Hideo Ide ◽  
Tohru Fukano
Keyword(s):  
Pressure Drop ◽  
Aspect Ratio ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Flow Phenomena

Both vertical upward and horizontal gas-liquid two-phase flows in a flat capillary rectangular channel were studied to clarify the flow phenomena, the holdup and the frictional pressure drop. The dimension of the channel used was 9.9 mm × 1.1 mm. The orientations of the channel were with the wide side vertical and the wide side horizontal. The differences between the flow characteristics in such orientations were investigated. New correlations of holdup and frictional pressure drop for flat capillary channels are proposed, in which the effect of aspect ratio has been taken into consideration.

Characteristics of Two-Phase Flow in Packed Bed Systems

2021 ◽  
Author(s):  
Noriaki Yasugi ◽  
Akito Fujitsu ◽  
Naoya Odaira ◽  
Daisuke Ito ◽  
Kei Ito ◽  
...  
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Two Phase Flow ◽  
Packed Bed ◽  
Phase Flow ◽  
Two Dimensional ◽  
High Speed Imaging ◽  
Two Phase ◽  
Dimensional Network ◽  
Interfacial Drag

Abstract Two-phase pressure drop in the debris has been studied by many researchers in relation to the debris cooling characteristics during a severe accident in a nuclear reactor. However, its flow regime transition of the two-phase flow in the debris has not been well understood, which strongly affects the interfacial drag and the pressure drop. Conventional models for gas-liquid two-phase flow pressure drop have not been established well to evaluate interfacial drag accurately. In this study, high-speed imaging of a two-dimensional network model was performed to clarify the effect of flow pattern on interfacial drag and pressure drop. Normally it would be very difficult to visualize such two-phase flow behavior in an ordinary packed bed due to the reflection/refraction of light and/or overlapping bubbles, even if the test section is made of transparent materials. Therefore, in this study, a test section, which simulates two-dimensional network of porous structures, was fabricated to avoid the overlapping bubbles. By using a high-speed imaging of the two-dimensional network model, two-phase flow pattern in the porous structure have been identified. From the experimental results, it was suggested that the interfacial drag term should be modified in the gas-liquid two-phase flow pressure drop model.

Measurement and Correlation of Pressure Drop for Gas-Liquid Two-phase Flow in Rectangular Microchannels

2010 ◽  
Vol 18 (6) ◽  
pp. 940-947 ◽  
Author(s):  
Youguang MA ◽  
Xiyan JI ◽  
Dongji WANG ◽  
Taotao FU ◽  
Chunying ZHU
Keyword(s):  
Pressure Drop ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Rectangular Microchannels

scholarly journals Experimental investigation of the two-phase flow regimes and pressure drop in horizontal mini-size rectangular test section

2012 ◽  
Vol 33 (2) ◽  
pp. 47-65
Author(s):  
Amr Mohamed Elazhary ◽  
Hassan M. Soliman
Keyword(s):  
Pressure Drop ◽  
Flow Regime ◽  
Test Section ◽  
Two Phase Flow ◽  
Rectangular Cross Section ◽  
Rectangular Channel ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Inlet Conditions

Abstract An experimental study was conducted in order to investigate two-phase flow regimes and fully developed pressure drop in a mini-size, horizontal rectangular channel. The test section was machined in the form of an impacting tee junction in an acrylic block (in order to facilitate visualization) with a rectangular cross-section of 1.87-mm height on 20-mm width on the inlet and outlet sides. Pressure drop measurement and flow regime identification were performed on all three sides of the junction. Air-water mixtures at 200 kPa (abs) and room temperature were used as the test fluids. Four flow regimes were identified visually: bubbly, plug, churn, and annular over the ranges of gas and liquid superficial velocities of 0.04 ≤ JG ≤ 10 m/s and 0.02 ≤ JL ≤ 0.7 m/s, respectively, and a flow regime map was developed. Accuracy of the pressure-measurement technique was validated with single-phase, laminar and turbulent, fully developed data. Two-phase experiments were conducted for eight different inlet conditions and various mass splits at the junction. Comparisons were conducted between the present data and former correlations for the fully developed two-phase pressure drop in rectangular channels with similar sizes. Wide deviations were found among these correlations, and the correlations that agreed best with the present data were identified.

Pressure Drop Characteristics of R134a Two-Phase Flow in a Horizontal Rectangular Microchannel

2002 ◽  
Author(s):  
X. Tu ◽  
P. Hrnjak
Keyword(s):  
Pressure Drop ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Homogeneous Model ◽  
Saturation Temperature ◽  
Phase Flow ◽  
Two Phase ◽  
Rectangular Microchannel ◽  
Turbulent Flow Regime ◽  
Parameter Ranges

Adiabatic two-phase flow pressure drop of R134a have been investigated experimentally in a rectangular channel with hydraulic diameter of 0.14 mm. Single-phase flow experiments were also conducted with liquid and vapor R134a, and an empirical correlation was developed for the turbulent flow regime. The parameter ranges examined for two-phase flow are: mass flux from 158 to 785 kg m−2 s−1; vapor quality from 0.01 to 0.95; and saturation temperature at about 24 ~ 32°C. The experimental data were compared with twelve existing correlations. The homogeneous model and the Mishima and Hibiki (1996) correlation give better predictions than any other correlations.

Measurement of Void Fraction and Pressure Drop of Air-Oil Two-Phase Flow in Horizontal Pipes

2004 ◽  
Vol 126 (1) ◽  
pp. 107-118 ◽  
Author(s):  
J. L. Pawloski ◽  
C. Y. Ching ◽  
M. Shoukri
Keyword(s):  
Pressure Drop ◽  
Flow Regime ◽  
Void Fraction ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Wide Range ◽  
Flow Regime Maps

The void fractions, flow regimes, and pressure drop of air-oil two-phase flow in a half-inch diameter pipe over a wide range of test conditions have been investigated. The flow regimes were identified with the aid of a 1000 frames per second high-speed camera. A capacitance sensor for instantaneous void fraction measurements was developed. The mean and probability density function of the instantaneous void fraction signal can be used to effectively identify the different flow regimes. The current flow regime data show significant differences in the transitional boundaries of the existing flow regime maps. Property correction factors for the flow regime maps are recommended. The pressure drop measurements were compared to the predictions from four existing two-phase flow pressure drop models. Though some of the models performed better for certain flow regimes, none of the models were found to give accurate results over the entire range of flow regimes.

scholarly journals Capillarity Effect on Two-Phase Flow Resistance in Microchannels

2007 ◽  
Author(s):  
Prakash Rapolu ◽  
Sang Young Son
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Energy Surface ◽  
Two Phase Flow ◽  
Surface Wettability ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pressure ◽  
Set Up ◽  
Phase Water

An experimental set-up is developed to investigate the effects of surface energy/surface wettability on characteristics of two-phase flow in microchannels. Two-phase (water and air) slug flow is established in entrance effect free microchannel test sections of various surface wettabilities. Pressure drop measurements and flow pattern detection by high speed visualization are employed to characterize the flow. Pressure drop of flow in hydrophilic channels is lesser than that of flow in hydrophobic channels. Significant change in contact line in advancing and receding interface section with surface wettability is observed.

scholarly journals Application of RQA and SOM for identification of two-phase flow patterns during boiling in horizontal minichannel

2021 ◽  
Vol 321 ◽  
pp. 02008
Author(s):  
Hubert Grzybowski ◽  
Iwona Zaborowska ◽  
Romuald Mosdorf
Keyword(s):  
Pressure Drop ◽  
Liquid Flow ◽  
Slug Flow ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Inner Diameter

In the paper, numerical methods of data analysis recurrence quantification analysis (RQA) and self-organizing map (SOM) have been used to analyse pressure drop oscillations during the flow boiling in minichannel. The performed analysis allows us to identify flow patterns based on the character of the pressure drop oscillations. The following two-phase flow patterns have been identified: liquid flow, liquid flow with small vapour bubble, slug flow, long slug flow and confined bubble flow. In the experiment, the open-loop boiling system in a circular horizontal minichannel with an inner diameter of 1 mm was investigated. The two-phase flow patterns at the outlet of the heated section were observed through the glass tube (with an inner diameter of 1 mm) and recorded by a high-speed camera Phantom v1610.

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