A CFD study of wave influence on film steam condensation in the presence of non-condensable gas

Wang, Xianmao; Chang, Ho; Corradini, Michael L.

doi:10.1016/j.nucengdes.2016.06.003

Cited by 30 publications

(6 citation statements)

References 20 publications

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“…It should be noted that in the data processing, grids with a liquid fraction greater than 0.5 are deleted so that the white area without data represents the liquid film area. The mass transfer in the non-condensable gas layer near the phase interface is related to the shapes of the phase interface, which is consistent with Wang et al (2016).…”

Section: Characteristics Of Liquid Filmsupporting

confidence: 83%

“…The wave motion can be observed when the local Reynolds number of the liquid film is greater than 30 (Bejan, 1995), which has a great influence on the heat transfer (Lee et al, 2015;Choi et al, 2020). Wang et al (2016) confirmed that the wave structure can enhance the condensation rate by up to ten percent and that the wave effects on film condensation should be included in the heat transfer analysis. Therefore, an accurate numerical calculation considering the gasliquid phase interface in the presence of non-condensable gas is necessary, which is close to the actual physical process.…”

Section: Introductionmentioning

confidence: 68%

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A numerical study on film condensation of steam with non-condensable gas on a vertical plate

Wei

Wang³

2023

Front. Energy Res.

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The film condensation of steam is very common in several industrial areas, such as condensers in power plants, seawater desalination, and air-conditioning systems. In some studies, the non-condensable gas and liquid film are overlooked for the sake of simplicity. To provide an integral computational scheme, in the present study, the film condensation of steam in the presence of non-condensable gas on a vertical plate has been simulated using a two-dimensional CFD model combining a wall condensation model and volume of fluid (VOF) model. After verification, the proposed computational scheme is used to simulate the steam condensation process, with the mass fractions of non-condensable gas varying from 5% to 45%. The results indicate that the concentration of non-condensable gas in the boundary layer decreases gradually with the condensation process, resulting in a decline in the synergy between temperature and velocity field. It can also be found that the fluctuation of the liquid film can influence the concentration distribution of the non-condensable gas layer. For cases with high concentrations of steam, the thermal resistance of liquid film can reach more than 20% of the total thermal resistance, which should not be ignored.

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Section: Characteristics Of Liquid Filmsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 68%

A numerical study on film condensation of steam with non-condensable gas on a vertical plate

Wei

Wang³

2023

Front. Energy Res.

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“…where T air,in,inlet and T air,in,outlet are the mass-weighted average temperatures of the air at the inlet and at the outlet of the pipe section, respectively, K. Finally, the convective heat transfer coefficient for the air inside the tube is derived using the Nusselt number Nu air,in h air,in = Nu air,in v air,in d pipe (7) where v air,in is a mean air velocity in the pipe, m/s. The Nusselt number for the finned side of the pipe is based on the correlations for cross flow over tube bundles [ (8) where Re air,out is the Reynolds number defined on the basis of maximum velocity that occurs in the pipe bundle (as the flow cross section area decreases due to existence of the pipes having external diameter D pipe ), Pr air,out stands for the Prantdl number defined for the temperature T bundle,av , while Pr pipe,wall is the Prantdl number defined for the temperature T pipe,wall,av . Symbols A, b and c denote correlation coefficients for the in-line bundle arrangement and they depend on the Re air,out value.…”

Section: Heat Transfer Coefficientsmentioning

confidence: 99%

“…Although limited when it comes to condensation hoods, the literature describes profusely the unit processes regarding other applications and appliances. The most important phenomena in terms of the condensation efficiency are: the model of condensation of the air-steam mixture coupled with the species transportation process [4][5][6][7][8], the heat transfer in externally-finned pipes with plain circular fins [9][10][11][12][13][14], and also tube bundle configuration analysis [15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Development of a Condensation Model and a New Design of a Condensation Hood—Numerical and Experimental Study

et al. 2021

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The development of a numerical model and design for the innovative construction of a heat exchanger (HE) used in a condensation hood (being a part of the combi-steamer) are described in this work. The model covers an air-steam flow, heat transfer, and a steam condensation process. The last two processes were implemented with the use of an in-house model introduced via User Defined Functions (UDF). As the condensate volume is negligible compared to the steam, the proposed model removes the condensate from the domain. This approach enabled the usage of a single-phase flow for both air and steam using a species transport model. As a consequence, a significant mesh and computation time reduction were achieved. The new heat exchanger is characterised by reorganised fluid flow and by externally finned pipes (contrary to the original construction, where internally finned pipes were used). This allowed a reduction in the number of the pipes from 48 to 5, which significantly simplifies construction and manufacturing process of the HE. The redesigned HE was tested in two cases: one simulating normal working conditions with a combi-steamer, the other with extremely high heat load. Measurement data showed that the numerical model predicted condensate mass flow rate (3.67 g/s computed and 3.56 g/s measured) and that the condensation capability increased at least by 15% when compared to the original HE design.

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“…Surface condensation occurs on surface walls, whereas capillary condensation occurs on surface pores. This capillary condensation or micro-condensation occurs on the porous surface walls [3,4].…”

Section: Introductionmentioning

confidence: 99%

Heat Flux Condensation on Coconut Shell Activated Charcoal Porous Media

Praswanto¹,

Asroni²,

Priyasmanu³

et al. 2020

JSAE

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One way to keep the air humidity is by increasing the heat transfer with the porous media model. Increasing heat transfer depends on the value of the heat flux on the porous media. The heat flux value can be determined by inserting the porous media into the test section and then flow the vapor. The amount of heat absorbed is influenced by the large diameter of the porous on the media used. Therefore, this study aimed to optimize coconut shell charcoal by activating the charcoal. The purpose of activating coconut shell charcoal is to enlarge the pores so that it absorbs heat better than charcoal that has not been activated. The research method used is an experimental method and compares the results of research with previous studies. The porous media was vaporized for 60 minutes with a vapor temperature of 30 °C, while the vapor speed was varied, namely 1 m/s, 2m/s and 3 m/s. From the research results, that by using coconut shell activated charcoal, the heat flux value was higher than using coconut shell charcoal media. This is because the pore size in activated charcoal is larger and more numerous than charcoal that has not been activated so that it absorbs more heat. In addition, the greater the vapor speed, the higher the heat flux, because in the test section more vapor enters than vapor that comes out so that the porous media has a long time to absorb heat in the vapor. The heat transfer that occurs in porous media includes forced convection heat transfer because it has a value of Gr/Re2 < 1.

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A CFD study of wave influence on film steam condensation in the presence of non-condensable gas

Cited by 30 publications

References 20 publications

A numerical study on film condensation of steam with non-condensable gas on a vertical plate

A numerical study on film condensation of steam with non-condensable gas on a vertical plate

Development of a Condensation Model and a New Design of a Condensation Hood—Numerical and Experimental Study

Heat Flux Condensation on Coconut Shell Activated Charcoal Porous Media

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