The effect of channel orientation on heat transfer and wall shear stress in the bubbly flow

Kashinsky, O. N.; Randin, V. V.; Chinak, A. V.

doi:10.1134/s086986431304001x

Cited by 9 publications

(3 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Intensification of the heat transfer in this region relates to the additional flow turbulisation by bubbles and the reorganisation of the liquid velocity profile which leads to the increase of the velocity gradient in the near wall region. Early a similar degree of the increasing of wall shear stress and heat transfer coefficient in turbulent two-phase bubbly flows was found in [40,41].…”

Section: Discussionsupporting

confidence: 69%

Experimental and Numerical Study of the Flow and Heat Transfer in a Bubbly Turbulent Flow in a Pipe with Sudden Expansion

2019

View full text Add to dashboard Cite

The flow patterns and heat transfer of a downstream bubbly flow in a sudden pipe expansion are experimentally and numerically studied. Measurements of the bubble size were performed using shadow photography. Fluid phase velocities were measured using a PIV system. The numerical model was employed the Eulerian approach. The set of RANS equations was used for modelling two-phase bubbly flows. The turbulence of the carrier liquid phase was predicted using the Reynolds stress model. The peak of axial and radial fluctuations of the carrier fluid (liquid) velocity in the bubbly flow is observed in the shear layer. The addition of air bubbles resulted in a significant increase in the heat transfer rate (up to 300%). The main enhancement in heat transfer is observed after the point of flow reattachment.Energies 2019, 12, 2735 2 of 18 regime. Gas concentration increased immediately after the cross-section of the flow separation. Measurements by [7] were performed in an upward, vertical flow of a liquid (water) and CO 2 bubbles. The distribution of the mean carrier fluid velocity was strongly dependent on the bubbles' diameter. A review of the literature for two-phase flow in sudden expansions and contractions was performed in [8]. Wang et al. [8] have found that none of the existing eight correlations can accurately predict the experimental database. Most of these correlations greatly overpredicted the results for mini test sections. Some of the correlations also underpredicted the data for large test sections.There are only a few papers that consider the numerical modeling of isothermal bubbly flows in a pipe with sudden expansion [9,10]. Krepper et al. [9] presented a mathematical model for polydisperse flow in a vertical pipe with sudden expansion. The numerical predictions for bubbly pipe flow with an obstacle demonstrated very difficult nature of such flows [9]. The Eulerian model was developed to simulate bubbly flows in a pipe with sudden expansion in [10]. Predictions were carried out using the CFD commercial package STAR-CCM+. The developed model was validated against measurements of Bel Fdhila [11]. The eddy-viscosity k−ε model showed poor reproduction of the bubbly flow structure because it disregarded much of the information on fluid flow turbulence. The Second-Moment Closure and LES methods captured the main characteristic turbulent length-scales responsible for the diffusion of the bubble gas phase, and moreover, these methods predicted the flow patterns and bubble distributions across the pipe section [10].Recently published numerical works [12,13] investigated heat transfer in bubbly flows without an abrupt pipe or channel expansion. These studies showed the significant influence of bubble diameter and gas volumetric flow rate ratios on the flow patterns and heat transfer. Heat transfer in bubbly flow increased up to three times that of one-phase fluid flow. The liquid turbulence was modeled using an isotropic k−ε model [12]. The DNS of bubbly flow with heat transfer was performed [13]. The numerical [14...

show abstract

Section: Discussionsupporting

confidence: 69%

Experimental and Numerical Study of the Flow and Heat Transfer in a Bubbly Turbulent Flow in a Pipe with Sudden Expansion

2019

View full text Add to dashboard Cite

show abstract

“…For experimental studies of heat transfer from the heated wall to the bubble flow, we used the test section, made of thin-walled stainless steel [7] (Fig. 1 b).…”

Section: Methodsmentioning

confidence: 99%

Heat transfer of bubbly flow on inner wall of annular channel

2017

View full text Add to dashboard Cite

Abstract. Experimental investigations of heat transfer from the heated wall to the two-phase bubbly flow were performed in vertical annular channel using air-water system. The IR-thermography and miniature temperature sensors were used to measure heat transfer coefficients. The influence of bubbles on heat transfer is shown in comparison with the case of single phase flow. The presence of bubbles in the flow leads to heat transfer intensification in the annular channel even for low void fractions.

show abstract

“…For the case of laminar natural convection it has been found that the injection of sub-milimeter bubbles enhances the heat transfer due to mixing and advection effects (Kitagawa and Murai, 2013). This effect is maximized when bubbles impact and slide along hot walls (Donnelly et al, 2009 in vertical and inclined channels have shown that for high void fraction of gas and low friction Reynolds numbers the effect on the heat transfer coefficient and the wall shear stress are strongly dependent on the inclination angle (Kashinsky et al, 2013(Kashinsky et al, , 2014. In the present work, the dependency of the flow and the heat transfer in low void fraction bubbly flows on the inclination angle of a channel are studied using direct numerical simulations.…”

Section: Introductionmentioning

confidence: 95%

Numerical study of the flow and heat transfer of bubbly flows in inclined channels

Piedra¹,

Ramos³

et al. 2015

International Journal of Heat and Fluid Flow

View full text Add to dashboard Cite

The effect of channel orientation on heat transfer and wall shear stress in the bubbly flow

Cited by 9 publications

References 1 publication

Experimental and Numerical Study of the Flow and Heat Transfer in a Bubbly Turbulent Flow in a Pipe with Sudden Expansion

Experimental and Numerical Study of the Flow and Heat Transfer in a Bubbly Turbulent Flow in a Pipe with Sudden Expansion

Heat transfer of bubbly flow on inner wall of annular channel

Numerical study of the flow and heat transfer of bubbly flows in inclined channels

Contact Info

Product

Resources

About