Bubble Diameter Effects on CFD Simulation for Subcooled Boiling Flow in Rolling Circular Tube

Eulerian two-fluid model coupled with wall boiling model was employed to calculate the three dimensional flow field and local parameter distribution with different bubble diameter models in circular tube under static and rolling condition. The wall boiling model utilized in this study was validated by Bartolomei experiment data, and a good agreement can be obtained. The calculation results of local void fraction are compared with experiment data to verify the accuracy of the numerical calculation for subcooled boiling flow under rolling condition. The Zeitoun bubble mean diameter model which the most recommended correlation for bubble diameter under low pressure and several fixed bubble diameters are applied to simulate the same condition in low pressure. These results are compared, include the distribution of void fraction, velocity distribution and radial flow induced by rolling motion. A good agreement with the experimental data has been achieved when Zeition bubble mean diameter and 2 mm fixed bubble diameter are used to describe vapor diameter in static condition. The local void fraction fluctuation has the same period with the rolling motion, and the fluctuation amplitude increases with the increase of rolling amplitude and rolling frequency. The difference shown in rolling condition between calculation results and experimental data demonstrates that better agreement with the experimental data has been achieved in the near-wall region about local void fraction which has bigger fluctuation amplitude. Higher void fraction has gotten using Zeition bubble mean diameter model to describe bubble diameter in subcooled boiling flow, tiny difference has showed in temperature, velocity and radial velocity in different bubble diameter model. Accurate vapor diameter model or method to describe vapor diameter coupled with suitable interphase force model is needed in rolling condition under low pressure to fit the calculation of subcooled boiling better under rolling condition.

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Analysis of RELAP5 Drift-Flux Model for Vertical Subcooled Boiling Flow at Low Pressure Conditions

10.1115/imece2000-1535 ◽

2000 ◽

Author(s):

Boštjan Končar ◽

Ivo Kljenak ◽

Borut Mavko

Keyword(s):

Void Fraction ◽

Drift Velocity ◽

Bubbly Flow ◽

Low Pressure ◽

Subcooled Boiling ◽

Drift Flux Model ◽

Drift Flux ◽

Boiling Flow ◽

Flux Model ◽

Relap5 Code

Abstract The RELAP5/MOD3.2.2 Gamma code was assessed against low pressure boiling flow experiments performed by Zeitoun and Shoukri (1997) in a vertical annulus. The predictions of subcooled boiling bubbly flow showed that the present version of the RELAP5 code underestimates the void fraction increase along the flow and strongly overestimates the vapor drift velocity. It is shown that in the calculations, a higher vapor drift velocity causes a lower interphase drag and may be a possible reason for underpredicted void fraction development. A modification is proposed, which introduces the replacement of the EPRI drift-flux formulation, which is currently incorporated in the RELAP5 code, with the Zuber-Findlay (1965) drift-flux model for the experimental low pressure conditions of the vertical bubbly flow regime. The improved experiment predictions with the modified RELAP5 code are presented and analysed.

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Modeling of low-pressure subcooled boiling flow of water via the homogeneous MUSIG approach

Nuclear Engineering and Design ◽

10.1016/j.nucengdes.2009.06.005 ◽

2009 ◽

Vol 239 (10) ◽

pp. 1733-1743 ◽

Cited By ~ 10

Author(s):

Erfeng Chen ◽

Yanzhong Li ◽

Xianghua Cheng ◽

Lei Wang

Keyword(s):

Low Pressure ◽

Subcooled Boiling ◽

Boiling Flow

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Mechanism study of bubble maximum diameter in the subcooled boiling flow for low-pressure condition

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2020.120585 ◽

2021 ◽

Vol 164 ◽

pp. 120585

Author(s):

Xiaomeng Dong ◽

Zhijian Zhang

Keyword(s):

Low Pressure ◽

Maximum Diameter ◽

Subcooled Boiling ◽

Pressure Condition ◽

Mechanism Study ◽

Boiling Flow

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Characteristics of Bubble Departure Frequency in a Low-Pressure Subcooled Boiling Flow

Journal of Nuclear Science and Technology ◽

10.1080/18811248.2010.9720958 ◽

2010 ◽

Vol 47 (7) ◽

pp. 608-617 ◽

Cited By ~ 23

Author(s):

Dongjin EUH ◽

Basar OZAR ◽

Takashi HIBIKI ◽

Mamoru ISHII ◽

Chul-Hwa SONG

Keyword(s):

Low Pressure ◽

Subcooled Boiling ◽

Boiling Flow

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Modelling of the Near-Wall Liquid Velocity Field in Subcooled Boiling Flow

Heat Transfer: Volume 2 ◽

10.1115/ht2005-72182 ◽

2005 ◽

Cited By ~ 6

Author(s):

Franz Ramstorfer ◽

Bernd Breitscha¨del ◽

Helfried Steiner ◽

Gu¨nter Brenn

Keyword(s):

Experimental Data ◽

Surface Roughness ◽

Flow Velocity ◽

Liquid Flow ◽

Axial Velocity ◽

Velocity Profiles ◽

Subcooled Boiling ◽

Test Channel ◽

Boiling Flow ◽

Near Wall

The subject of the present work is the modelling of the liquid streamwise flow velocity in the two-phase boundary layer in subcooled boiling flow under the influence of the vapor bubbles. Subcooled boiling flow experiments were carried out in a horizontal test channel in order to investigate the interaction between the bubbles and the liquid phase. The heater surface was located at the bottom of the test channel. The near-wall liquid flow velocity was measured using a two-component laser-Doppler anemometer. Based on the experimental data a model is proposed to describe the impact of the gaseous phase on the motion of the liquid in the subcooled boiling regime. It was observed that the axial velocity profiles near the wall follow a logarithmic law similar to that used in turbulent single-phase flow over rough surfaces. Based on this finding it is suggested to model the influence of the bubbles on the liquid flow analogously to the effect of a surface roughness. The correlation developed for an equivalent surface roughness associated with the bubbles yields good agreement of the modeled axial velocity profiles with the experimental data.

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Investigation on Bubble Diameter Distribution in Upward Flow by the Two-Fluid and Multi-Fluid Models

Energies ◽

10.3390/en14185776 ◽

2021 ◽

Vol 14 (18) ◽

pp. 5776

Author(s):

Yongzhong Zeng ◽

Weilin Xu

Keyword(s):

Experimental Data ◽

Volume Fraction ◽

Fluid Model ◽

Bubble Diameter ◽

Diameter Distribution ◽

Bubble Flow ◽

Calculation Results ◽

Two Fluid Model ◽

Gas Volume ◽

Two Fluid

Bubble flow can be simulated by the two-fluid model and the multi-fluid model based on the Eulerian method. In this paper, the gas phase was further divided into several groups of dispersed phases according to the diameter by using the Eulerian-Eulerian (E-E) multi-fluid model. The diameters of bubbles in each group were considered to be the same, and their distributions were reorganized according to a specific probability density function. The experimental data of two kinds of bubble flow with different characteristics were used to verify the model. With the help of the open-source CFD software, OpenFOAM-7.x (OpenFOAM-7.0, produced by OpenFOAM foundation, Reading, England), the influences of the group number, the probability distribution function, and the parameters of different bubble diameters on the calculation results were studied. Meanwhile, the numerical simulation results were compared with the two-fluid model and the experimental data. The results show that for the bubble flow with the unimodal distribution, both the multi-fluid model and the two-fluid model can obtain the distribution of gas volume fraction along the pipe radius. The calculation results of the multi-fluid model agree with the experimental data, while those of the two-fluid model differ greatly from the experimental data, which verifies the advantage of the multi-fluid model in calculating the distribution of gas volume fraction in the polydisperse bubble flow. Meanwhile, the multi-fluid model can be used to accurately predict the distribution of the parameters of each phase of the bubble flow if the reasonable bubble diameter distribution is provided and the appropriate interphase force calculation model is determined.

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A Mechanistic Model for Predicting Subcooled Boiling Flow

Volume 2: Symposia, Parts A, B, and C ◽

10.1115/fedsm2003-45571 ◽

2003 ◽

Author(s):

G. H. Yeoh ◽

J. Y. Tu

Keyword(s):

Void Fraction ◽

Liquid Velocity ◽

Fluid Model ◽

Mechanistic Model ◽

Three Dimensional ◽

Annular Channel ◽

Heat Fluxes ◽

Group Model ◽

Subcooled Boiling ◽

Boiling Flow

Population balance equations combined with a three-dimensional two-fluid model are employed to predict subcooled boiling flow at low pressure in a vertical annular channel. The MUSIG (MUltiple-SIze-Group) model implemented in CFX4.4 is extended to account for the wall nucleation and condensation in the subcooled boiling regime. Comparison of model predictions against local measurements is made for the void fraction, bubble Sauter diameter and gas and liquid velocities covering a range of different mass and heat fluxes and inlet subcoolings. Good agreement is achieved with the local radial void fraction, bubble Sauter diameter and liquid velocity profiles against measurements. However, significant weakness of the model is evidenced in the prediction of the vapor velocity. Work is in progress to circumvent the deficiency of the extended MUSIG model by the consideration of an algebraic slip model to account for bubble separation.

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Subcooled Boiling Flow Heat Transfer From Plain and Enhanced Surfaces in Automotive Applications

Journal of Heat Transfer ◽

10.1115/1.2780178 ◽

2008 ◽

Vol 130 (1) ◽

Cited By ~ 14

Author(s):

Franz Ramstorfer ◽

Helfried Steiner ◽

Günter Brenn ◽

Claudius Kormann ◽

Franz Rammer

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Nucleate Boiling ◽

Heated Wall ◽

Transfer Model ◽

Subcooled Boiling ◽

Cooling Systems ◽

Porous Coatings ◽

Transfer Rates ◽

Boiling Flow

The requirement for the highest possible heat transfer rates in compact, efficient cooling systems can often only be met by providing for a transition to subcooled boiling flow in strongly heated wall regions. The significantly higher heat transfer rates achievable with boiling can help keep the temperatures of the structure on an acceptable level. It has been shown in many experimental studies that special surface finish or porous coatings on the heated surfaces can intensify the nucleate boiling process markedly. Most of those experiments were carried out with water or refrigerants. The present work investigates the potential of this method to enhance the subcooled boiling heat transfer in automotive cooling systems using a mixture of ethylene-glycol and de-ionized water as the coolant. Subcooled boiling flow experiments were carried out in a vertical test channel considering two different types of coated surfaces and one uncoated surface as a reference. The experimental results of the present work clearly demonstrate that the concept of enhancing boiling by modifying the microstructure of the heated surface can be successfully applied to automotive cooling systems. The observed increase in the heat transfer rates differ markedly for the two considered porous coatings, though. Based on the experimental data, a heat transfer model for subcooled boiling flow using a power-additive superposition approach is proposed. The model assumes the total wall heat flux as a nonlinear combination of a convective and a nucleate boiling contribution, both obtained from well-established semiempirical correlations. The wall heat fluxes predicted by the proposed model are in very good agreement with the experimental data for all considered flow conditions and surface types.

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