Track 6- Thermal Hydraulic Analysis and Testing Experiment Study on the Condensation Heat Transfer with Accumulated Noncondensable Gas in a Vertical Tube Kwon-Yeong Lee and Moo Hwan Kim* Mechanical Engineering Department, Pohang University of Science and Technology Pohang 790-784, ROK * Corresponding author: Phone +82-054-279-2165, FAX. +82-054-279-3199, E-mail: email@example.com ABSTRACT It has been well known that even a small amount of noncondensable gas can reduce the condensation heat transfer considerably. In the condenser tube the condensate flows as an annular liquid film adjacent to the tube wall and the steam-noncondensable gas mixture flows in the core region. Then the reduction is mainly caused by a noncondensable gas layer formed adjacent to the liquid-gas interface. Recently, several researches have been performed for the condensation in the presence of noncondensable gas taken place inside a vertical tube. Pure steam condensation mode and mixture bypass mode have been studied mainly. This research has been performed to study the heat transfer characteristics for a PRHRS condensation heat exchanger in a SMART. The remaining heat is removed from the core passively by the PRHRS in a period of serious accidence of the SMART. Three different kinds of mode are expected during the operation of the PRHRS - pure steam mode, mixture bypass mode, and noncondensable gas accumulated and remained mode. The main subject of this study is about the last mode that the noncondensable gas is accumulated and remained inside the vertical tube because the condensate fills the bottom of the tube. The experimental facilities consisted of a steam generation part, a steam flow rate control part, a steam-nitrogen mixing part, a test section, and a data acquisition system. The condenser tube of the test section is a 304 stainless steel pipe with 13 mm inner diameter, 2.5 mm thickness, and 3 m length. A 40 mm inner diameter concentric acryl jacket surrounded the test condenser. The local heat fluxes were calculated from the local coolant bulk temperatures at the midpoint of the annular gap, and a small amount of air was injected through the annulus with the coolant to enhance turbulence and mixing. In the mainly focused mode, the noncondensable gas was solved and removed with the condensate water. So the solubility of noncondensable gas should be considered. The heat transfer coefficients decreased as the nitrogen volumetric fraction inside the condenser tube increased. The heat flux increased as the inlet mixture Reynolds number increased.
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