Investigation of flow boiling in horizontal tubes: Part I—A new diabatic two-phase flow pattern map

Wojtan, Leszek; Ursenbacher, Thierry; Thome, John R.

doi:10.1016/j.ijheatmasstransfer.2004.12.012

Cited by 443 publications

(261 citation statements)

References 11 publications

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“…The aforementioned observation was not unexpected due to the highly non-linear nature of the Rouhani and Axelsson (1970) in this region of vapour quality. Five observed data points out of a total of 18 data points (a total of 18 unique flow conditions with two successive measurements taken for each respective flow condition resulting in a total of 36 data points) did not match the predictions of the modified Wojtan et al (2005) flow pattern map (Figure 4). The aforementioned exceptions could be isolated to the predictions of intermittent flow, which were difficult to classify using subjective visual means.…”

Section: Data Validationmentioning

confidence: 94%

The influence of inclination angle on void fraction and heat transfer during condensation inside a smooth tube

Olivier

Meyer

Paepe

et al. 2016

International Journal of Multiphase Flow

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Most work in literature on condensation in tubes has been done for smooth tubes in the horizontal and vertical configurations. Recent experimental works with condensation at different inclination angles showed that the heat transfer characteristics were a function of inclination angle. These works were limited to heat transfer and pressure drop measurements with visual observations. However, no work has been done on measuring the void fractions during condensation at different inclination angles. The purpose of this study was to measure void fractions and heat transfer coefficients during condensation for tube inclinations ranging from vertical downwards (-90ᵒ) to vertical upwards (90ᵒ) at a saturation temperature of 40 ᵒC. Measurements were taken in an experimental set-up in which condensation occurred on the inside of a test section. The test section was a circular tube with an inner diameter of 8.38 mm and a heat transfer length of 1.488. The refrigerant used was R134a, and the void fractions were measured using two capacitive void fraction sensors. Mass fluxes ranging from 100 -400 kg/m 2 .s and vapour qualities ranging from 10 -90% were considered. Heat transfer coefficients were also compared with void fractions. It was found that at combinations of low mass fluxes and vapour qualities, void fraction and heat transfer were significantly affected by changes in inclination angle. Generally, void fractions and heat transfer coefficients increased with downward inclination angles with an optimum angle between -10ᵒ and -30ᵒ (downward flow). At some intermediate mass flux and vapour quality conditions, the void fraction and heat transfer coefficients were observed to be independent of the inclination angle despite changes in the prevailing flow patterns.2

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Section: Data Validationmentioning

confidence: 94%

The influence of inclination angle on void fraction and heat transfer during condensation inside a smooth tube

Olivier

Meyer

Paepe

et al. 2016

International Journal of Multiphase Flow

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“…The maximum pressure drop occurs around 60% of vapor quality regardless of orientation. According to the flow pattern map of [13], this maximum occurs for annular flow regime at the inlet of the bend. The 1087 pressure drop data points measured in horizontal and vertical return bends ( ,) for refrigerants HFO-1234yf, R134a and R-410A were compared against four two-phase frictional pressure drop prediction methods in return bends [14 [15[16[17[18].…”

Section: Perturbation Lengthsmentioning

confidence: 99%

Two-Phase Flow Characteristics in Singularities

Revellin¹,

Padilla²,

Bonjour³

2015

Encyclopedia of Two-Phase Heat Transfer and Flow II

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“…To obtain the two-phase heat transfer coefficient the procedures as described by Wojtan et al [16,17] are used, which builds on the work of Kattan et al [18] and Zürcher et al [19]. The process for obtaining the two-phase heat transfer coefficient is quite involved and only the most important equations are stated here.…”

Section: Heat Transfer Coefficients -Two-phase Regionmentioning

confidence: 99%

Second law analysis and optimization of a parabolic trough receiver tube for direct steam generation

2014

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Entropy generation in the receiver tube of a parabolic trough solar collector can mainly be attributed to the fluid friction and finite temperature differences. The contribution of each of these components is investigated under different circumstances. Mass flow rates, tube diameters and operating pressures are investigated to obtain good guidelines for receiver tube and plant design. Operating pressures between 3 MPa (saturation temperature of 233.9 °C) and 9 MPa (saturation temperature of 303.3 °C) were investigated.Results show that small diameters can result in excessive fluid friction, especially when the mass flow rates are high. For most cases, tube diameters beyond 20 mm will exclusively be subject to entropy generation due to finite temperature differences, and entropy generation due to fluid friction will be small to negligible. Increasing the concentration ratio will decrease entropy generation, due to a higher heat flux per unit meter. This will ultimately result in shorter receiver tube lengths. From a simulated annealing (SA) optimization it was seen that if the diameter is increased, the entropy generation can be lowered, provided that the concentration ratio is kept constant. However, beyond a certain point gains in minimizing the entropy generation become negligible. The optimal operating pressure will generally increase if the mass flow rate is increased. Finally it was seen that higher operating pressures are more advantageous when the entropy generation minimization is considered in conjunction with the work output.

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Investigation of flow boiling in horizontal tubes: Part I—A new diabatic two-phase flow pattern map

Cited by 443 publications

References 11 publications

The influence of inclination angle on void fraction and heat transfer during condensation inside a smooth tube

The influence of inclination angle on void fraction and heat transfer during condensation inside a smooth tube

Two-Phase Flow Characteristics in Singularities

Second law analysis and optimization of a parabolic trough receiver tube for direct steam generation

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