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 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.

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.

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.

scholarly journals Development of the pressure drop model for two-phase flow through a packed bed with small particles

2014 ◽  
Vol 80 (817) ◽  
pp. FE0258-FE0258
Author(s):  
Hideaki HOSOI ◽  
Naoyuki ISHIDA ◽  
Tetsushi HORIBE ◽  
Shigeru SHIMOKAWARA ◽  
Tamotsu CHIBA
Keyword(s):  
Pressure Drop ◽  
Two Phase Flow ◽  
Packed Bed ◽  
Phase Flow ◽  
Small Particles ◽  
Two Phase ◽  
Flow Through

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

2002 ◽  
Author(s):  
J. Pawloski ◽  
C. Ching ◽  
M. Shoukri
Keyword(s):  
Pressure Drop ◽  
Flow Regime ◽  
Void Fraction ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Average Error ◽  
Phase Flow ◽  
Two Phase ◽  
Wide Range

The 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. The current flow regime data show significant differences in the transitional boundaries from the flow regime maps of Mandhane et al. (1974), Taitel and Dukler (1974) and Spedding and Nguyen (1980). The pressure drop measurements were compared to the predictions from four existing pressure drop models: Homogeneous, Martinelli (1948), Chisolm (1973) and Olujic (1985). The Chisolm and Martinelli models were found to be the most accurate, with an average error of about 35 percent. A capacitance sensor for instantaneous void fraction measurement was developed. Results indicate the data from the sensor could be used to identify the different flow regimes.

Sign in / Sign up

Export Citation Format

Share Document