Visualization and Numerical Simulations of Condensing Flow in Small Diameter Channels

Toninelli, Paolo; Bortolin, Stefano; Azzolin, Marco

doi:10.1080/01457632.2018.1443255

Cited by 17 publications

(6 citation statements)

References 22 publications

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“…The two distinct mechanisms that caused this effect were interfacial shear stress and turbulent effective conductivity. As reported by the simulation of Toninelli et al [14], the Reynolds number increased with an increase mass flux, causing an enhancement of the turbulent intensity, which enhanced the effective thermal conductivity. Additionally, an increase in the mass flux increased the relative velocity of the liquid/vapor, which can be expressed as follows:…”

Section: Heat Transfer Coefficientsupporting

confidence: 51%

Experimental Investigation of Two-Phase Flow Boiling Heat Transfer Coefficient and Pressure Drop of R448A inside Multiport Mini-Channel Tube

Hoang

Agustiarini

2022

Energies

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Regulations and restrictions against high global warming potential (GWP) refrigerants have been introduced to encourage the adoption of environmentally friendly refrigerants and mitigate the environmental impact of the HVAC industry. R448A, a zeotropic blend with a GWP of 1390, has recently been proposed as a drop-in replacement for R404A and R410A in commercial systems. In this study, the heat transfer coefficient and pressure drop characteristics of R448A within a multiport mini-channel tube were experimentally investigated. The experimental ranges of the mass and heat fluxes were 100 to 500 kg/(m2s) and 3–15 kW/m2, respectively. Additionally, the range of quality from 0 to 1 was considered at two fixed saturated temperatures of 3 and 6 °C. The heat transfer coefficient increased with mass flux. Under low mass flux condition, the heat flux increased the heat transfer coefficient, but there was no noticeable effect of the saturated temperature on the heat transfer coefficient. At high mass flux, heat flux had no major effect on heat transfer, while a decrease in the saturated temperature was found to increase the heat transfer coefficient. Moreover, the pressure drop increased with an increase in the mass flux and vapor quality, whereas the heat flux did not affect the pressure drop. The heat transfer coefficient and pressure drop performance of R448A was compared with that of R410A inside the same tube. Finally, correlations for heat transfer coefficient and pressure drop were proposed for the prediction of heat transfer coefficient and pressure drop in practical applications.

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Section: Heat Transfer Coefficientsupporting

confidence: 51%

Experimental Investigation of Two-Phase Flow Boiling Heat Transfer Coefficient and Pressure Drop of R448A inside Multiport Mini-Channel Tube

Hoang

Agustiarini

2022

Energies

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“…Turbulent effects in the liquid and vapor flows during the condensation process were considered using the SST k ~ω model, similarly to Da Riva and Del Col 31 . Similarly, Toninelli et al 20,34 concluded that the gravity effect on the condensation heat transfer and liquid phase distribution of R134a was more significant for a 3.38 mm inner diameter channel compared to a 1 mm minichannel. However, although the liquid film thinning at the top of the channel observed for the larger diameter tube due to gravity, the heat transfer coefficient in the 1 mm minichannel was higher than the one in the 3.38 mm tube due to the lower average liquid film thickness.…”

Section: Numerical and Analytical Studiesmentioning

confidence: 93%

“…Extensive experimental and theoretical research has been performed to investigate the influence of gravity on the interfacial behavior and flow condensation heat transfer by varying the tube inclination angle during on-ground experiments 15 – 19 (see Table 1 ). When stratified smooth or stratified wavy flow occurs, the liquid is drained at the bottom of the tube due to gravity and a thin film of condensate is formed at the top of the tube, leading to an increase in the heat transfer coefficient 20 . When the flow regime changes to churn, intermittent or annular flows, the liquid phase sporadically or entirely covers the inner circumference of the channel, thus increasing the local thermal resistance and consequently decreasing the condensation heat transfer rate 21 .…”

Section: Introductionmentioning

confidence: 99%

“… Park et al 17 Experimental Circular 11.89 mm ID channel FC-72 Horizontal, vertical downflow and upflow P sat = 102–171.93 kPa G = 13.32–343.79 kg m −2 s −1 HTC measurements Flow visualizations At low G values, the three orientations yield significant differences in heat transfer performance; at high G values the local HTCs tend to converge for the three orientations. Toninelli et al 20 Experimental and numerical Circular 1 mm and 3.4 mm ID channels R134a Horizontal T sat = 40 °C T wall = 30 °C G = 100 kg m −2 s −1 x = 0.6 HTC measurements Flow visualizations Numerical simulations of FWC by means of VOF method The gravity effect on the liquid distribution is significant for the 3.38 mm tube, but the HTCs are smaller compared to 1 mm minichannel due to the higher average liquid film thickness. …”

Section: Introductionmentioning

confidence: 99%

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Condensation heat transfer in microgravity conditions

et al. 2023

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In the present paper, a thorough review of the experimental and numerical studies dealing with filmwise and dropwise condensation under microgravity is reported, covering mechanisms both inside tubes and on plain or enhanced surfaces. The gravity effect on the condensation heat transfer is examined considering the results of studies conducted both in terrestrial environment and in the absence of gravity. From the literature, it can be inferred that the influence of gravity on the condensation heat transfer inside tubes can be limited by increasing the mass flux of the operating fluid and, at equal mass flux, by decreasing the channel diameter. There are flow conditions at which gravity does exert a negligible effect during in-tube condensation: predictive tools for identifying such conditions and for the evaluation of the condensation heat transfer coefficient are also discussed. With regard to dropwise condensation, if liquid removal depends on gravity, this prevents its application in low gravity space systems. Alternatively, droplets can be removed by the high vapor velocity or by passive techniques based on the use of condensing surfaces with wettability gradients or micrometric/nanometric structuration: these represent an interesting solution for exploiting the benefits of dropwise condensation in terms of heat transfer enhancement and equipment compactness in microgravitational environments. The experimental investigation of the condensation heat transfer for long durations in steady-state zero-gravity conditions, such as inside the International Space Station, may compensate the substantial lack of repeatable experimental data and allow the development of reliable design tools for space applications.

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“…The findings suggested that gravity had minimal influence in the square minichannel, with heat transfer primarily governed by shear stress and surface tension under the considered mass flux conditions. Tonelli et al [65] conducted steady-state numerical simulations to analyse R134a condensation within horizontal channels. They explored the impact of hydraulic diameters ranging between 1 and 3.4 mm on two-phase fluid flow and heat transfer.…”

Section: Numerical Studies Focused On Mini/microchannel Condensation ...mentioning

confidence: 99%

Condensation Flow of Refrigerants Inside Mini and Microchannels: A Review

Başaran,

Benim

2024

Applied Sciences

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Nowadays, the demand for obtaining high heat flux values in small volumes has increased with the development of technology. Condensing flow inside mini- and microchannels has been becoming a promising solution for refrigeration, HVAC, air-conditioning, heat pumps, heat pipes, and electronic cooling applications. In these applications, employing mini/microchannels in the condenser design results in the working fluid, generally refrigerant, undergoing a phase change inside the mini/microchannels. On the other hand, the reduction in the hydraulic diameter during condensation gives rise to different flow regimes and heat transfer mechanisms in the mini- and microchannels compared to the conventional channels. Therefore, the understanding of fluid flow and heat transfer characteristics during condensation of refrigerant inside mini- and microchannels has been gaining importance in terms of condenser design. This study presents a state-of-the-art review of condensation studies on refrigerants inside mini- and microchannels. The review includes experimental studies as well as correlation models, which are developed to predict condensation heat transfer coefficients and pressure drop. The refrigerant type, thermodynamical performance, and compatibility, as well as the environmental effects of refrigerant, play a decisive role in the design of refrigeration systems. Therefore, the environmental impacts of refrigerants and current regulations against them are also discussed in the present review.

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Visualization and Numerical Simulations of Condensing Flow in Small Diameter Channels

Cited by 17 publications

References 22 publications

Experimental Investigation of Two-Phase Flow Boiling Heat Transfer Coefficient and Pressure Drop of R448A inside Multiport Mini-Channel Tube

Experimental Investigation of Two-Phase Flow Boiling Heat Transfer Coefficient and Pressure Drop of R448A inside Multiport Mini-Channel Tube

Condensation heat transfer in microgravity conditions

Condensation Flow of Refrigerants Inside Mini and Microchannels: A Review

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