Mechanism Study on Condensation Heat Transfer on Shell Side of Spiral Wound Heat Exchanger : Visualization of Film Behavior

Abstract

Because of compact design and easy to modulization, the Spiral Wound Heat Exchanger (SWHX) is used as a steam generator and passive residual heat removal system (PRHRS) in light water Small Modular Reactors (SMRs) and nuclear ships. When used as a PRHRS, the shell side is mainly connected with the primary system. In an accident situation, two phase steam flows down through the shell-side and its cooled down by condensation phenomena. To design proper PRHRS, it is important to evaluate and predict the condensation performance.

In this study, to analysis the condensation heat transfer mechanism on shell side of SWHX, heat transfer evaluation and visualization experiment are conducted. In order to reflect real SWHX to test-section, 6 coiled tubes are installed in one layer, and it are cut in 60° to mimic spacing bars which support coiled tubes to make stable structure. The experiment is conducted with pressurized steam. The steam is condensed at little super-heated condition and the condition covers velocity of 4 ~ 18 m/s and pressure of 3 bar. Coolant is injected to each coiled tube with same conditions. At the heat transfer experiment, heat transfer coefficients of each tube are measured. In addition, film behavior is observed by high-speed camera (PHANTOM) at frond and side of test-section. Visualization experiment is conducted with Nd:YAG laser and light source. From the experimental results, condensation heat transfer trend of each tube is discussed with film behavior.