Thermal hydraulic characteristics of air–water two-phase flows in helical pipes

Jayakumar, J. S.; Mahajani, Sanjay M.; Mandal, J.C.; Iyer, Kannan N.; Vijayan, P.K.

doi:10.1016/j.cherd.2009.09.007

Cited by 31 publications

(8 citation statements)

References 23 publications

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“…Jayakumar et al [23][24] also studied the single-phase and two-phase (water-air) flows inside vertical helical pipes numerically and determined the influence of the void fraction (within a small range) and some geometrical characteristics on the pressure loss. They developed a correlation for estimating the overall and local Nusselt numbers as functions of the angular location and heat transfer coefficient for a fluid flow through helically coiled heat exchangers.…”

Section: Introductionmentioning

confidence: 98%

Numerical study of the influence of geometrical characteristics of a vertical helical coil on a bubbly flow

Saffari

Moosavi

2014

J Appl Mech Tech Phy

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In this article, turbulent single-phase and two-phase (air-water) bubbly fluid flows in a vertical helical coil are analyzed by using computational fluid dynamics (CFD). The effects of the pipe diameter, coil diameter, coil pitch, Reynolds number, and void fraction on the pressure loss, friction coefficient, and flow characteristics are investigated. The Eulerian-Eulerian model is used in this work to simulate the two-phase fluid flow. Three-dimensional governing equations of continuity, momentum, and energy are solved by using the finite volume method. The k-ε turbulence model is used to calculate turbulence fluctuations. The SIMPLE algorithm is employed to solve the velocity and pressure fields. Due to the effect of a secondary force in helical pipes, the friction coefficient is found to be higher in helical pipes than in straight pipes. The friction coefficient increases with an increase in the curvature, pipe diameter, and coil pitch and decreases with an increase in the coil diameter and void fraction. The close correlation between the numerical results obtained in this study and the numerical and empirical results of other researchers confirm the accuracy of the applied method. For void fractions up to 0.1, the numerical results indicate that the friction coefficient increases with increasing the pipe diameter and keeping the coil pitch and diameter constant and decreases with increasing the coil diameter. Finally, with an increase in the Reynolds number, the friction coefficient decreases, while the void fraction increases.

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Section: Introductionmentioning

confidence: 98%

Numerical study of the influence of geometrical characteristics of a vertical helical coil on a bubbly flow

Saffari

Moosavi

2014

J Appl Mech Tech Phy

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“…They reported the formation of a liquid film on the outer portion of the tube and a good agreement with average void fraction experimental data. Jayakumar et al (2010) presented a CFD analysis for the heat transfer of an airewater two-phase mixture flowing through a helically coiled heat exchanger, identifying the effect of different geometrical parameters. Validation against experiments is provided for the frictional pressure drop and the heat transfer coefficient.…”

Section: Introductionmentioning

confidence: 99%

CFD study of an air–water flow inside helically coiled pipes

Colombo

Cammi

Guédon

et al. 2015

Progress in Nuclear Energy

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a b s t r a c tCFD is used to study an airewater mixture flowing inside helically coiled pipes, being at the moment considered for the Steam Generators (SGs) of different nuclear reactor projects of Generation IIIþ and Generation IV. The two-phase mixture is described through the EulerianeEulerian model and the adiabatic flow is simulated through the ANSYS FLUENT code. A twofold objective is pursued. On the one hand, obtaining an accurate estimation of physical quantities such as the frictional pressure drop and the void fraction. In this regard, CFD simulations can provide accurate predictions without being limited to a particular range of system parameters, which often constricts the application of empirical correlations. On the other hand, a better understanding of the role of the centrifugal force field and its effect on the two-phase flow field and the phase distributions is pursued.The effect of the centrifugal force field introduced by the geometry is characterized. Water is pushed by the centrifugal force towards the outer pipe wall, whereas air accumulates in the inner region of the pipe. The maximum of the mixture velocity is therefore shifted towards the inner pipe wall, as the air flows much faster than the water, having a considerably lower density. The flow field, as for the singlephase flow, is characterized by flow recirculation and vortices. Quantitatively, the simulation results are validated against the experimental data of Akagawa et al. (1971) for the void fraction and the frictional pressure drop. The relatively simple model of momentum interfacial transfer allows obtaining a very good agreement for the average void fraction and a satisfactory estimation of the frictional pressure drop and, at the same time, limits the computational cost of the simulations. Effects of changes in the diameter of the dispersed phase are described, as its value strongly affects the degree of interaction between the phases. In addition, a more precise treatment of the near wall region other than wall function results in a better definition of the liquid film at the wall, although an overestimation of the frictional pressure drop is obtained.

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“…Heat transfer calculations for the two-phase flow are validated against experimental results of flow through an annular pipe (Jayakumar et al, 2010b). In the section 3 details of heat transfer characteristics along the length of the pipe for single-phase fluid have been presented.…”

Section: Estimation Of Two-phase Heat Transfer Coefficientmentioning

confidence: 99%

“…A numerical study can give much more insight into the phenomena and further, the influence of various parameters can also be studied. Jayakumar et al (2008bJayakumar et al ( , 2010b) have carried out heat transfer studies of flow of two-phase air-water mixture through helical coils. This paper gives a clear picture on the influence of velocity, temperature and void fraction on the coil parameters.…”

Section: Air-water Two-phase Flow and Heat Transfermentioning

confidence: 99%

“…They established the effect of centrifugal acceleration on the flow regime map and brought out the spatial and temporal flow structure distribution. Jayakumar et al (2010b) has reported numerical investigation of heat transfer to two-phase air-water mixture flowing through helical pipes. In that work, the variation of phasic velocity, temperature and void fraction at various cross-sections along the length of tube are presented.…”

Section: Pressure Drop and Heat Transfer For Air-water Two-phase Flowmentioning

confidence: 99%

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