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International Heat Transfer Conference 11

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

INTERACTION BETWEEN NATURAL CIRCULATION AND CONDENSATION HEAT TRANSFER IN THE PASSIVE CONTAINMENT COOLING CONDENSERS

J. L. Munoz-Cobo
Polytechnic University of Valencia, Department of Chemical and Nuclear Engineering, Camino de Vera 14, 46022 Valencia, Spain

S. Chiva
Department of Chemical & Nuclear Engineering Polytechnic University of Valencia P.O. Box 22012 46071 Valencia Spain

A. Escriva
Polytechnic University of Valencia, Department of Chemical and Nuclear Engineering, Camino de Vera 14, 46022 Valencia, Spain

Jose Corberan
Universidad Politecnica de Valencia

DOI: 10.1615/IHTC11.590
pages 443-449

Abstrakt

The passive containment cooling condensers (PCCCs) are the crucial part of several new reactor designs, like the European Simplified Boiling Water Reactor (ESBWR) and the SBWR. Each PCCC is formed by several vertical tubes connected to an upper plenum that receives the steam from a distributor, and a lower plenum where the condensate, the uncondensed steam and the noncondensable gases (NC) are discharged. These PCCCs are submerged in a large pool. Inside the vertical tubes of the PCCC, we have condensation in presence of NC gases with concurrent downflow (Munoz-Cobo et al., 1996), (Chiva et al., 1997). Outside the condenser tubes we have several heat transfer regimes, in the lower part of the tubes near the tube exit, we have laminar natural convection. The physical reason for this behavior is that in this region the heat transfer (sensible + condensation) is very small, and therefore the buoyancy term in the condensation equations is small and the flow is laminar. The second region is the turbulent region, where the natural convection flow becomes turbulent, and the boundary layer thickness increases with distance. In the third region, about one half-meter from the tube entrance, we have interaction among the boundary layers of the neighbouring tubes. In this region the turbulent boundary layers of the neighbouring tubes overlap, producing an enhanced turbulent region with strong circulating currents. Then when the upper part of the pool reach the saturation temperature, we have pool boiling in this region.
We have developed several models to compute the heat transfer coefficients for the following regimes: i) condensation in presence of noncondensable gases inside the tubes, ii) laminar natural convection for vertical cylinders, iii) turbulent natural convection for vertical cylinders, (Munoz-Cobo et al., 1996), (Chiva et al., 1997), (Mills, 1995). These models have been implemented in the TRAC-BF1 code and have been extensively validated with experimental data and 2D calculation with the FLUENT code.
Finally we have developed a PCCC model suitable for the TRAC-BF1 code, which performs all the functions of a real PCCC. With this model we have studied the interaction between the condensation regime inside and the natural convection outside the tubes.

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