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[en] Reflux and vent condensers are vertical separators where film condensation occurs. A vapour mixture is supplied at the bottom of the tubes and encounters vertical cold surfaces. A falling film forms and exits from the bottom of the tubes, flowing counter-current to the vapour, but co-current to the coolant on the shell side. Flooding occurs when the condensate flow moves from a gravity regime to a shear regime. Vapour velocities at or above the flooding velocity will cause the liquid to exit from the top of the tubes rather than from the bottom. The main disadvantage of these condensers is the limited flooding velocity allowed. Several investigators propose correlations to predict the flooding velocity. In most cases these correlations come from isothermal experiments data, thus the general recommendation of using safety factors of at least 30%. This work compares these correlations to new experimental values of flooding in steam/air vent condensation. The experimental apparatus is a 3 m long, double-pipe condenser with an internal diameter of 0.028 m. The conclusions presented here will aid the design engineer to understand better the applicability of the discussed correlations in the design of steam/air vent condensers
Journal
[en] Local condensation heat transfer rates are measured for steam-air mixtures in direct contact with subcooled water layers inside a vertical tube over a wide range of liquid flow rates. The gas mixture is maintained effectively stagnant during the tests and the major resistance to heat transfer is due to the large amount of noncondensables. A theoretical model is developed to account for some additional thermal resistance on the liquid side, by decomposing the liquid film into a wavy 'nonresistant' region and a substrate region where temperature gradients may prevail. Heat transfer coefficients are found to depend not only on the steam concentration but also on the liquid flow rate. Interestingly, wave characteristics of the falling liquid layer, such as the dominant wave velocity and frequency, demonstrate that condensation may only be responsible for minor modifications of the isothermal liquid surface morphology. Furthermore, the dependence of heat transfer coefficients on the liquid flow rate is attributed to the dynamic interaction between the interfacial waves and the gas layer. This notion is utilized by correlating measured gas Sherwood numbers with the gas Grashof number and a dimensionless parameter which characterizes the interface. (author)
Journal
International Journal of Heat and Mass Transfer; ISSN 0017-9310; 
; CODEN IJHMAK; v. 38(5); p. 779-794
; CODEN IJHMAK; v. 38(5); p. 779-794
[en] The RIMAP project is aimed at the establishment of an European RBMI framework including the assessment of the Consequence of Failure (CoF). Although the RIMAP framework allows the use of various methods provided they meet certain requirements, specific methods to assess the CoF have been developed. Both for a screening analysis and a detailed analysis a RIMAP-compliant method is described. The field of application covers the full range of equipment types, including static equipment, rotating equipment and safety instrumented functions. In a worked example the use of the detailed RIMAP method is demonstrated for the case of steam containments as being applied in the power industry
Journal
International Journal of Pressure Vessels and Piping; ISSN 0308-0161; ; CODEN PRVPAS; v. 81(10-11); p. 787-796
; CODEN PRVPAS; v. 81(10-11); p. 787-796
[en] There is dealt with the effect of series connection of surface and jet condensers for nuclear power plants. It will be shown that series connection of jet condensers has got considerable advantages as compared to series connection of surface condensers with respect to physical behavior as well as cost. (orig./HP)
[de]
Behandelt wird die Auswirkung der Reihenschaltung bei Oberflaechen- und Mischkondensatoren fuer KKW. Dabei zeigt sich, dass die Reihenschaltung von Mischkondensatoren gegenueber der Reihenschaltung von Oberflaechenkondensatoren erhebliche Vorteile sowohl hinsichtlich des physikalischen Verhaltens wie auch der Kosten bringt. (orig./HP)Journal
Brennstoff-Waerme-Kraft; ISSN 0006-9612; ; v. 32(3); p. 111-115
; v. 32(3); p. 111-115
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