scholarly journals Numerical simulation of two-phase slug flow with liquid carryover in different diameter ratio T-junction

2017 ◽  
Vol 908 ◽  
pp. 012037 ◽  
Author(s):  
W Pao ◽  
L Hon ◽  
A Saieed ◽  
S Ban
Keyword(s):  
Numerical Simulation ◽  
Slug Flow ◽  
Diameter Ratio ◽  
Two Phase

Modelling of Pressure Fluctuation With Cross Flow in a Tight-Lattice Rod Bundle

2008 ◽  
Author(s):  
Weizhong Zhang ◽  
Hiroyuki Yoshida ◽  
Kazuyuki Takase
Keyword(s):  
Numerical Simulation ◽  
Pressure Gradient ◽  
Pressure Fluctuation ◽  
Slug Flow ◽  
Reactor Core ◽  
Approximate Model ◽  
Differential Pressure ◽  
Liquid Slug ◽  
Two Phase ◽  
Simulation Code

An approximate model is presented which permits the prediction in detail of the unsteady differential pressure fluctuation behavior between subchannels in the nuclear reactor core. The instantaneous fluctuation of differential pressure between two subchannels in gas-liquid slug flow regime is deemed as a result of the intermittent nature slug flow in each subchannel. The model is based on the detailed numerical simulation result of two-phase flow that pressure drop occurs mainly in liquid slug region and in the bubble region it is negligibly small. The instantaneous fluctuation of differential pressure between the two subchannels is associated with pressure gradient in the liquid slug for each channel. In addition to a hydrostatic gradient, acceleration and frictional gradients are taken into account to predict pressure gradient in the liquid slug. This model temporarily used in conjunction with the numerical simulation code works satisfactorily to reproduce numerical simulation results for instantaneous fluctuation of differential pressure between two modeled subchannels.

NUMERICAL SIMULATION OF TWO-PHASE SLUG FLOW USING A HYBRID CODE BASED ON SLUG TRACKING AND SLUG CAPTURING METHODOLOGIES

2016 ◽  
Author(s):  
Vinicius Almeida ◽  
Marco Germano Conte ◽  
Fausto Arinos Barbuto ◽  
Rigoberto Morales
Keyword(s):  
Numerical Simulation ◽  
Slug Flow ◽  
Two Phase ◽  
Hybrid Code

Two-Phase Cross Flow Between Subchannels in a Tight-Lattice Rod Bundle

2009 ◽  
Author(s):  
Weizhong Zhang ◽  
Hiroyuki Yoshida ◽  
Kazuyuki Takase
Keyword(s):  
Numerical Simulation ◽  
Pressure Gradient ◽  
Slug Flow ◽  
Cross Flow ◽  
Differential Pressure ◽  
Liquid Slug ◽  
Two Phase ◽  
Rod Bundle ◽  
Simulation Results ◽  
Tight Lattice

In relation to the thermal-hydraulic design of an innovative Flexible-fuel-cycle Water Reactor (FLWR), this study investigates inter-subchannel cross flow phenomena in a tight-lattice rod bundle. Numerical simulations of cross flow using advance interface tracking method were performed and the results were analyzed by a statistical method to clarify the characteristics of inter-subchannel two phase cross flow in the FLWR reactor core. It was revealed that strong correlation exists between differential pressure and gas/liquid mixing coefficients, and cross flow results mechanistically from differential pressure between subchannels. An approximate model is presented which permits the prediction in detail of the components of the inter-subchannel fluctuation differential pressure. The instantaneous fluctuation of differential pressure between two subchannels in gas-liquid slug flow regime is deemed as a result of the intermittent nature of slug flow in each subchannel. The model is based on the detailed numerical simulation results that pressure drop occurs mainly in liquid slug region and in the bubble region it is negligibly small. The instantaneous fluctuation of differential pressure is associated with pressure gradient in the liquid slug for each channel. In addition to a hydrostatic gradient, acceleration and frictional gradients are taken into account to predict pressure gradient in the liquid slug. This model used in conjunction with the numerical simulation code works satisfactorily to reproduce numerical simulation results for instantaneous fluctuation of differential pressure between two modeled subchannels.

Numerical Simulation of Flow Regime Transition From Slug to Wavy Flow in Helically Coiled Tubes

2016 ◽  
Author(s):  
Zhaoxu Li ◽  
Hongye Zhu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Centrifugal Force ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Pressurized Water Reactor ◽  
Two Phase ◽  
Pressurized Water

Two-phase flow in helically coiled tubes is becoming the interest of many investigators because of its importance in various applications, such as nuclear engineering, chemical engineering, refrigerating engineering and power engineering. Compared with U-type tubes used in pressurized water reactor (PWR), helically coiled tubes have advantages in size, heat transfer capacity, thermal stress toleration and two-phase stability. Accordingly the helically coiled tubes have been utilized in the steam generators of the next general reactors, such as gas-cooled reactor, fast breeder reactor and integrated pressurized water reactor. In helically coiled tubes the characteristics of momentum and heat transfer are distinct from those in straight tubes due to the presence of centrifugal force, especially for two-phase flow. Meanwhile, the transitions of flow regime, which is the crucial knowledge for the designers to determine the heat transfer rates and flow resistance, are also significantly affected by the centrifugal force. In this study, two-phase flow regimes in helically coiled tubes are investigated. Computational fluid dynamics (CFD), using fractional volume of fluid (VOF) model, is carried out to simulate wavy and slug flow regimes in helically coiled tubes. The corresponding experiment is also conducted to visualize these flow regimes at different superficial flow velocities. Numerical simulation results actually reflect the influence of centrifugal force on the two-phase flow and show a good agreement with the photographs captured from the experiment. Based on the simulations at different superficial flow velocities, the boundary between the slug and wavy flow regimes is predicted, in addition, compared with that in inclined tubes. The comparison indicates that centrifugal force could induce the appearance of wavy flows in advance and prompt the transition from slug flow to wavy flow.

CFD Modeling of Two-Phase Gas-Liquid Slug Flow Using VOF Method in Microchannels

2009 ◽  
Author(s):  
A. Mehdizadeh ◽  
S. A. Sherif ◽  
W. E. Lear
Keyword(s):  
Numerical Simulation ◽  
Liquid Film ◽  
Slug Flow ◽  
Thin Liquid Film ◽  
Liquid Films ◽  
Vof Method ◽  
Cfd Modeling ◽  
Two Phase ◽  
Mesh Resolution ◽  
Gas Volume

Despite of the fact that numerical simulation of two-phase flows in microchannels has been attempted by many investigators, most efforts seem to have failed in correctly capturing the flow physics, especially the slug flow regime characteristics. The presence of a thin liquid film in the order of 10 μm around the bubble (sometimes called gas pocket or gas slug) may be a contributing factor to the above difficulty. Typically, liquid films have a significant effect on the flow field. Thus, there is a strong motivation to employ numerical simulation methods in order to avoid some of the experimental difficulties. In this paper, the characteristics of two-phase slug flows in microchannels are calculated with the help of the Volume-of-Fluid (VOF) method. Formation of the slugs for different superficial velocities, Capillary numbers, and gas volume fractions are investigated. The minimum mesh resolution required to capture the liquid film surrounding the gas bubble is reported employing a dynamic mesh adaption methodology with interface tracking. Results are shown to be in good agreement with experimental data and empirical correlations.

Experimental investigation on the effect of diameter ratio on two-phase slug flow separation in a T-Junction

2018 ◽  
Vol 170 ◽  
pp. 139-150 ◽  
Author(s):  
Ahmed Saieed ◽  
William Pao ◽  
Buddhika Hewakandamby ◽  
Barry J. Azzopardi ◽  
David A. Wood ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Flow Separation ◽  
Slug Flow ◽  
Diameter Ratio ◽  
Two Phase

Numerical evaluation of separation efficiency in converging T-junction with slug flow

2019 ◽  
Vol 30 (7) ◽  
pp. 3515-3534
Author(s):  
William Pao ◽  
Zeeshan Qadir Memon
Keyword(s):  
Phase Separation ◽  
Slug Flow ◽  
Separation Efficiency ◽  
Diameter Ratio ◽  
Flow Loop ◽  
Two Phase ◽  
Content Type ◽  
Production Platform ◽  
Major Factors ◽  
Phase Separator

Purpose Excessive liquid carryover in T-junction presents a serious operational issue in offshore production platform. Slug flow and diameter ratio of T-junction are considered as two major factors causing liquid carryover. Regular and reduced T-junction are being used as partial phase separator but their efficiency is low. Converging T-junction with two distinct diameters (primary and secondary) in branch arm is used to improve the phase separation efficiency. The motivation is to combine specific feature of regular and reduced T-junction to increase separation efficiency of existing T-junction without involving too much operational workover. The purpose of this paper is to numerically evaluate the separation efficiency of a converging T-junction design. The present model and its methodology was validated with in-house experimental data for 3 inches diameter flow loop. Design/methodology/approach The slug flow regime was simulated using incompressible Eulerian mixture model coupled with volume of fluid method to capture the dynamic gas-liquid interface. Findings The analyses concluded that T-junction with primary-secondary branch arm diameters combination of 1.0-0.5 and 0.67-0.40 managed to achieve 95 per cent separation efficiency. The research also confirmed that over reduction of T-junction secondary diameter ratio below 0.2 will lead to decrease in separation efficiency. Research limitations/implications The present research is limit to air/water two-phase flow but the general results should be applicable for wider application. Practical implications The proposed design limited excessive workover and installation for current and existing T-junction. Hence, cutting down installation cost while improving the separation efficiency. Social implications The present research resulted in higher separation efficiency, cutting down production down time and lead to operational cost saving. Originality/value The present research proposes an original and new T-junction design that can increase phase separation efficiency to over 90 per cent. The finding also confirmed that there is a limitation whereby smaller diameter ratio T-junction does not always resulted in better separation.

Numerical simulation of two-phase separation in a small diameter ratio T-junction

2017 ◽  
Vol 48 (3-4) ◽  
pp. 255-260 ◽  
Author(s):  
W. Pao ◽  
A. Saieed ◽  
F. M. Hashim ◽  
R. B. M. Norpiah
Keyword(s):  
Numerical Simulation ◽  
Phase Separation ◽  
Small Diameter ◽  
Diameter Ratio ◽  
Two Phase
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