Flow pattern visualization and heat transfer characteristics of R-134a during evaporation inside a smooth tube with different tube inclinations

Mohseni, S.G.; Akhavan-Behabadi, M.A.

doi:10.1016/j.icheatmasstransfer.2014.10.018

Cited by 28 publications

(7 citation statements)

References 11 publications

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Section: Romanmentioning

confidence: 99%

“…In diabatic configuration, the studies of Bhagwat and Ghajar [7,8] and Mohseni and Akhavan-Behabadi [9] were published more recently. Bhagwat and Ghajar [7,8] presented a study about heated air-water flow pattern transitions in a 12.7 mm inner diameter channel while Mohseni and Akhavan-Behabadi [9] study deals with R134a flow boiling in a 8.9 mm inner diameter channel. Both studies show a certain agreement with the observations which were previously done in adiabatic configuration with a σ surface tension (N.m -1 ) φ heat flux (W.m -2 ) Φ two-phase flow multiplier (-) pred predicted sat saturation test test top top tot total vap vapour Δp differential pressure taps pronounced effect of inclination on flow patterns for low-inertia flows.…”

Section: Romanmentioning

confidence: 99%

“…Both studies show a certain agreement with the observations which were previously done in adiabatic configuration with a σ surface tension (N.m -1 ) φ heat flux (W.m -2 ) Φ two-phase flow multiplier (-) pred predicted sat saturation test test top top tot total vap vapour Δp differential pressure taps pronounced effect of inclination on flow patterns for low-inertia flows. However, like most studies of the literature, the visualisation section of Mohseni and Akhavan-Behabadi [9] is located at the outlet of the test section. Consequently, the flow in the evaporator and the effect of heat flux cannot be directly analysed.…”

Section: Romanmentioning

confidence: 99%

See 2 more Smart Citations

Experimental study of flow boiling in an inclined mini-channel: Effect of inclination on flow pattern transitions and pressure drops

Layssac

Lips

Revellin

2018

Experimental Thermal and Fluid Science

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An experimental study of R245fa two-phase flow in a 1.6 mm inner diameter circular channel is presented in both adiabatic and diabatic conditions. The test section is composed of a sapphire tube coated with ITO, which enables a total transparency of the evaporator. The effect of inclination on the flow patterns and the pressure drops is presented and discussed for various vapour qualities and mass velocities and a saturation temperature of 81°C, corresponding to a Bond number of 4.2. For each experimental conditions, the pressure drops are measured and the flow is visualised under eleven configurations of inclination from the vertical downward flow (-90°) to the vertical upward flow (+90°). The flow pattern transitions are compared with two flow pattern maps available in the literature. The effect of the heat flux on the flow patterns is analysed and shows the disappearance of the stratified flow for the downward flows in the case of low-inertia flows. A study of the effect of the inclination on the total and frictional pressure gradients is also led. The observations are compared with several models of the literature. These models show a good agreement to predict the pressure gradient for upward flows. Finally, the effect of the heat flux on the pressure drop variations with inclination is analysed. It shows a general increase of the pressure drops due to gravity and frictional forces with the heat flux for low vapour qualities, whatever the considered inclination. This offset decreases with the vapour quality.

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Section: Romanmentioning

confidence: 99%

Section: Romanmentioning

confidence: 99%

Section: Romanmentioning

confidence: 99%

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Experimental study of flow boiling in an inclined mini-channel: Effect of inclination on flow pattern transitions and pressure drops

Layssac

Lips

Revellin

2018

Experimental Thermal and Fluid Science

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“…Inclination is an option when designing condenser tubes that cannot be oriented horizontally or vertically owing to space constraints, operating conditions, performance optimization, or environmental conditions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Examples in which condensation occurs in inclined tubes include steam condensers used for air-cooling, certain rooftop industrial air-cooled refrigeration systems, and in the condensers of motor vehicles and trucks driving up and down hills.…”

Section: Introductionmentioning

confidence: 99%

Condensation heat transfer coefficients in an inclined smooth tube at low mass fluxes

Ewim

Meyer

Abadi

2018

International Journal of Heat and Mass Transfer

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The purpose of this study was to present the heat transfer coefficients and flow patterns during the condensation of R134a inside an inclined smooth tube at low mass fluxes and different temperature differences (the temperature differences were between the saturation temperature and wall temperature). Condensation experiments were conducted at different inclination angles ranging from −90° (vertically downwards) to +90° (vertically upwards), at low mass fluxes of 50, 75, and 100 kg/m 2 s, and temperature differences from 1 °C to 10 °C. Measurements were taken at different mean vapour qualities between 0.1 to 0.9 in a smooth tube test section with an internal diameter of 8.38 mm and length of 1.5 m. The average saturation temperature was kept constant at 40 °C. It was found that inclination significantly influenced the flow patterns and the heat transfer coefficients. Downwards flows accounted for an increase in heat transfer coefficient with the maximum heat transfer coefficient found at inclinations of −15° and −30° (downwards flow) at the corresponding minimum temperature difference was tested for in each case. The maximum inclination effect was approximately 60% and was obtained at the lowest mass flux of 50 kg/m 2 s. In general, it was concluded that the heat transfer coefficients were more sensitive to the temperature difference for downwards flows than for upwards flows. Furthermore, there was no significant effect of temperature difference on the heat transfer coefficients for upwards flows. It was also found that the downwards and upwards vertical orientations were almost independent of the temperature difference. With respect to the inclination effect, it was found that in general, it decreased with an increase in temperature difference but decreased with an increase in mass flux and vapour quality.

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“…Thisdifference of behaviour may be due to the different phenomenology between micro and macro-channel two-phase flows. In macro-scale[15,17,19,22], the two-phase flow is mainly annular or stratified while in micro-scale slug flows were observed[16,20]. The effect of inclination may be interpreted in terms of partial dry-out of the upper part of the tube in macro-scale.…”

mentioning

confidence: 97%

Effect of inclination on heat transfer coefficient during flow boiling in a mini-channel

Layssac

Lips

Revellin

2019

International Journal of Heat and Mass Transfer

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An experimental study of heat transfer during R245fa flow boiling is carried out in a 1.6 mm inner diameter circular channel (198 original data points). The test section is composed of a sapphire tube coated with ITO, which enables a total transparency of the evaporator in the visible spectrum. The acquisition of the outer wall temperature field is ensured by means of an infrared camera and the heat transfer coefficient is calculated by means of a local thermal model. The effect of the inclination on the heat transfer is presented and discussed for various vapour qualities and mass velocities and a saturation temperature of 81°C, corresponding to a Bond number of 4.1. For each experimental condition, the mean heat transfer coefficient is calculated for various inclinations from the vertical downward flow (-90°) to the vertical upward flow (+90°). The variation of the heat transfer coefficient are first presented and analyzed in the horizontal case. The heat transfer coefficient variations with the flow parameters are interpreted in terms of nucleate and convective boiling and these observations are confirmed by the visualisation of the nucleation phenomenon in the evaporator. The inclination has almost no effect on the heat transfer and this lack of effect is finally interpreted in terms of shift between the annular to intermittent flow pattern transition coupled with the nucleate to convective boiling transition.

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Flow pattern visualization and heat transfer characteristics of R-134a during evaporation inside a smooth tube with different tube inclinations

Cited by 28 publications

References 11 publications

Experimental study of flow boiling in an inclined mini-channel: Effect of inclination on flow pattern transitions and pressure drops

Experimental study of flow boiling in an inclined mini-channel: Effect of inclination on flow pattern transitions and pressure drops

Condensation heat transfer coefficients in an inclined smooth tube at low mass fluxes

Effect of inclination on heat transfer coefficient during flow boiling in a mini-channel

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