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Multidimensional effects in laminar filmwise condensation of vapor in binary and ternary mixtures with non-condensable gases
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.ORCID iD: 0000-0001-5595-1952
2008 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 238, no 6, 1373-1381 p.Article in journal (Refereed) Published
Abstract [en]

This paper is dealing with the multidimensional modelling of gravity driven water vapour free convection condensation from binary and ternary mixtures of condensable and noncondensable gases. In the case of ternary mixtures, a special attention is paid to the influence of the light gas on the transport phenomena in the gaseous phase. Two solution methods have been applied: an analytical solution employing the boundary layer similarity approximation and a numerical solution of multi-fluid, multi-component formulation of the conservation equations. It has been demonstrated that the two methods are equivalent when applied to binary mixtures in simple geometries. However, to capture the spatial effects and the ternary mixture phenomena the latter method must be used.

Place, publisher, year, edition, pages
2008. Vol. 238, no 6, 1373-1381 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-7457DOI: 10.1016/j.nucengdes.2007.11.003ISI: 000256122700010Scopus ID: 2-s2.0-42249111344OAI: oai:DiVA.org:kth-7457DiVA: diva2:12487
Note

QC 20100623

Available from: 2007-09-10 Created: 2007-09-10 Last updated: 2016-06-09Bibliographically approved
In thesis
1. Theoretical investigation of water vapour condensation in presence of noncondensable gases
Open this publication in new window or tab >>Theoretical investigation of water vapour condensation in presence of noncondensable gases
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Steam condensation phenomenon plays an important role in many industrial applications. Especially in energy sector this process requires deep understanding. When noncondensable gases are taken into consideration description of the entire phenomenon becomes more complicated. If the surface condensation is taken into consideration this additional species accumulates and creates noncondensable layer near the surface on water vapour condenses. Due to this effect heat and mass transfer rates from gas mixture decreases. Also volume condensation (if it occurs) is affected by the presence of inert gases.

Several examples where the phenomena described above are important can be taken into consideration: studies of accidents in the nuclear power plants where condensation in the volume and condensation on the cold containment’s structures occurs after steam is released due to the pipe brake in the primary loop (especially this is important for PWR’s containments which in normal operation conditions are filled with air or nitrogen); condensation of steam in the pipe systems of BWR reactors where some amount of hydrogen can be accumulated due to the water vapour condensation in nonvented pipes; condensation of steam in the condensers after low pressure stage turbine; etc. Also in other fields, e.g. chemistry or meteorology, the condensation of water vapour in presence of noncondensable species plays very important role.

Diffusion surface condensation model and its implementation into CFX – 4 CFD code has been described in this licentiate thesis. Three different situations have been taken into account: surface condensation of water vapour in presence of air on the vertical wall (computational results have been compared with several commonly used correlations), surface condensation of water vapour in presence of air on the horizontal wall (results have been compared with experimental data), volume condensation in presence of air (known also as spontaneous condensation) – principle of the model has been described and calculation example has been presented and analysed.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 64 p.
Keyword
Technology, TEKNIKVETENSKAP
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-321 (URN)91-7178-050-0 (ISBN)
Presentation
2005-05-19, Sal B1, Brinellvägen 23, Stockholm, 10:00
Note
QC 20100623Available from: 2005-07-20 Created: 2005-07-20 Last updated: 2012-02-14Bibliographically approved
2. Mechanistic Modeling of Water Vapour Condensation in Presence of Noncondensable Gases
Open this publication in new window or tab >>Mechanistic Modeling of Water Vapour Condensation in Presence of Noncondensable Gases
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis concerns the analytical and numerical analysis of the water vapour condensation from the multicomponent mixture of condensable and noncondensable gases in the area of the nuclear reactor thermal-hydraulic safety.

Following an extensive literature review in this field three aspects of the condensation phenomenon have been taken into consideration: a surface condensation, a liquid condensate interaction with gaseous mixtures and a spontaneous condensation in supersaturated mixtures. In all these cases condensation heat and mass transfer rates are significantly dependent on the local mixture intensive parameters like for example the noncondensable species concentration.

In order to analyze the multicomponent mixture distribution in the above-mentioned conditions, appropriate simplified physical and mathematical models have been formulated. Two mixture compositions have been taken into account: a binary mixture of water vapour with heavy noncondensable gas and a ternary mixture with two noncondensable gases with different molecular weights. For the binary mixture a special attention has been focused on the heavy gas accumulation in the near-interface region and the influence of liquid film instabilities on the interface heat and mass transfer phenomena. For the ternary mixture of gases a special attention has been paid to the influence of the light gas and induced buoyancy forces on the condensation heat and mass transfer processes.

Both analytical and numerical methods have been used in order to find solutions to these problems. The analytical part has been performed applying the boundary layer approximation and the similarity method to the system of film and mixture conservation equations. The numerical analysis has been performed with the in-house developed code and commercial CFD software. Performing analytical and CFD calculations it has been found that most important processes which govern the multicomponent gas distribution and condensation heat transfer degradation are directly related to the interaction between interface mass balances and buoyancy forces. It has been observed that if the influence of the liquid film instabilities is taken into consideration the heat transfer enhancement due to the presence of different types of waves is directly related to the internal film hydrodynamics and shows up in the mixture-side heat transfer coefficient. The model developed for the dispersed phase growth shows that degradation of the condensation heat transfer rate, which is a consequence of degradation of the convective mass flux, should be taken into account for highly supersaturated gaseous mixtures and can be captured by combination with the mechanistic CFD surface condensation model.

Keywords: condensation, noncondensable gases, CFD simulation, boundary-layer approximation, binary and ternary mixtures

Place, publisher, year, edition, pages
Stockholm: KTH, 2007
Series
TRITA-FYS, ISSN 0280-316X ; 2007:63
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-4483 (URN)978-91-7178-747-7 (ISBN)
Public defence
2007-09-27, FD5, Albanova University Center, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Note

QC 20100623

Available from: 2007-09-10 Created: 2007-09-10 Last updated: 2015-01-30Bibliographically approved

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Anglart, Henryk

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