Condensation heat transfer of R245fa in tubes with and without lyophilic porous-membrane-tube insert

Xie, Jian; Xu, Jinliang; Cheng, Yu; Feng, Xi‐Qiao; He, Xiaotian

doi:10.1016/j.ijheatmasstransfer.2015.04.081

Cited by 25 publications

(5 citation statements)

References 33 publications

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“…Under this circumstance, the larger fins act mainly as a 'bridge' for the second flow region. The flow pattern, which is similar to the enhanced condensation tube investigated by Xu and his co-workers [25][26][27][28][29], is likely to be modified from the wavy flow pattern.…”

Section: Results Of the Eight-fin Tubesupporting

confidence: 68%

“…Their results showed that the heat transfer coefficients could be more than two times those in the bare smooth tube. Xie et al [29] also performed a condensation experiment using R245fa with a modulated heat transfer tube that had a porous membrane tube in the center core. With the increase in vapor void fractions near the tube wall, the modulated heat transfer tube had up to 85% improvement in condensation heat transfer coefficients as compared to the bare tube.…”

Section: Nomenclaturementioning

confidence: 99%

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Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting

Wang

Leong

et al. 2018

International Journal of Heat and Mass Transfer

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Section: Results Of the Eight-fin Tubesupporting

confidence: 68%

Section: Nomenclaturementioning

confidence: 99%

Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting

Wang

Leong

et al. 2018

International Journal of Heat and Mass Transfer

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“…The outlet mixture enthalpy and quality are calculated as follows (31) where kw is the thermal conductivity of the microtube, hto is the total heat transfer coefficient, and hc is the heat transfer coefficient of cooling water. The calculation of hto and hc can be found in Ref 62 . Pressure drops were correlated based on the Chisholm method, where the two-phase multiplier ratio is expressed as: where Dgas,f is the friction pressure drop if the vapor phase flows alone.…”

Section: Data Reductionmentioning

confidence: 99%

Parametric study on hydrothermal properties of condensing flow in microtube heat exchangers using numerical and experimental approaches

Sadaghiani¹

2021

Preprint

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Microchannels have increasingly been used to miniaturize heat transfer equipment, improve energy efficiency, and minimize heat transfer fluid inventory. A fundamental understanding of condensation in microscale will yield far-reaching benefits for the different areas of industry. In this study, microtubes with inner diameters of 250, 500, 600, and 900 µm were used to investigate the effect of microtube diameter, inlet quality, and mass flux on the liquid/vapor interface near the wall boundaries in condensing flow. After validation with the experimental results, a transient numerical model (based on the volume of fluid approach) was developed to investigate the hydrothermal properties of condensing such as bubble dynamics, flow map transitions, transient interface shear force, and temperature on flow condensation performance in terms of heat transfer coefficient and pressure drop. The liquid film thickness, slug velocity, and location of transition from annular flow to slug flow inside the microtube were characterized for different microtubes, and the resultant alteration in condensation flow heat transfer and pressure drop is discussed in detail. The obtained results indicated that the interfacial characteristics of condensing flow in microtubes with hydraulic diameters lower than 500µm are majorly different from those with D>500µm.

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“…Lee et al [18] used a nanoscale surface to increase the heat transfer rate in dropwise condensation. Xie et al [19] investigated the condensation heat transfer performance of R245fa foam insulation in tubes with and without lyophilic porousmembrane-tube inserts, respectively. Wen et al [20] investigated the condensation heat transfer performance by using hydrophobic copper nanowires to induce a capillary force.…”

Section: Introductionmentioning

confidence: 99%

Analytical Investigation into Effects of Capillary Force on Condensate Film Flowing over Horizontal Semicircular Tube in Porous Medium

Chang

Shiue

Ciou

et al. 2021

Mathematical Problems in Engineering

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A theoretical investigation is performed into the problem of laminar filmwise condensation flow over a horizontal semicircular tube embedded in a porous medium and subject to capillary forces. The effects of the capillary force and gravity force on the condensation heat transfer performance are analyzed using an energy balance approach method. For analytical convenience, several dimensionless parameters are introduced, including the Jakob number Ja, Rayleigh number Ra, and capillary force parameter Boc. The resulting dimensionless governing equation is solved using the numerical shooting method to determine the effect of capillary forces on the condensate thickness. A capillary suction velocity can be obtained mathematically in the calculation process and indicates whether the gravity force is greater than the capillary force. It is shown that if the capillary force is greater than the condensate gravity force, the liquid condensate will be sucked into the two-phase zone. Under this condition, the condensate film thickness reduces and the heat transfer performance is correspondingly improved. Without considering the capillary force effects, the mean Nusselt number is also obtained in the present study as N u ¯ | V 2 ∗ = 0 = 2 R a D a / J a 1 / 2 ∫ 0 π 1 + cos θ 1 / 2 d θ .

show abstract

Condensation heat transfer of R245fa in tubes with and without lyophilic porous-membrane-tube insert

Cited by 25 publications

References 33 publications

Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting

Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting

Parametric study on hydrothermal properties of condensing flow in microtube heat exchangers using numerical and experimental approaches

Analytical Investigation into Effects of Capillary Force on Condensate Film Flowing over Horizontal Semicircular Tube in Porous Medium

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