Contents lists available at ScienceDirect Nuclear Engineering and Design journal homepage: www.elsevier.com/locate/nucengdes Performance analyses of a steam condensation tube immersed in a saturated water pool: Effects of tube inclination Muritala Alade Amidu, Junseok Park, Youngjae Park, Changhwan Lim, Satbyoul Jung, Hyungdae Kim ⁎ Department of Nuclear Engineering, Kyung Hee University, Yongin, Republic of Korea ARTICLE INFO Keywords: Passive containment cooling water storage tank Thermal performance Tube inclination Two-phase heat exchanger ABSTRACT Two-phase heat exchanger immersed in a passive containment cooling water storage tank (PCCWST) is a key component of the passive containment cooling system (PCCS) in light water reactors. Condensation and boiling heat transfer phenomena taking place on the inside and outside walls are crucial to the performance of the heat exchanger tube. The performances of such phenomena can be readily affected by the inclination angle of the heat exchanger tube under buoyancy-driven convection conditions in a PCCWST. However, to date no systematic examination of the effects of inclination angle on pool heat exchanger performance has been reported. This paper presents the results of numerical and experimental analyses of how inclination angle affects the perfor- mance of a single steam condensation tube immersed in a saturated water pool. To concurrently predict the two- phase heat transfer processes inside and outside the heat exchanger tube, an explicit heat structure coupling of two thermal-hydraulic codes was implemented using open media models. An experimental facility was also constructed to test a single-tube heat exchanger under the same conditions as the simulation. A comparison of simulation data and experimental results obtained for the reference case (tube inclination of 30°) confirmed that the coupled code could predict the heat transfer rate in the pool heat exchanger within the error limits of the experimental measurements. In light of this, additional simulations and experiments were conducted at varying inclination angles, from 3° to 90°. The results of simulations and experimental studies revealed that the heat transfer rate of a heat exchanger tube in a saturated pool is hardly influenced by tube inclination. Although an increase in inclination angle caused the vapor slug to spread around the heat exchanger tube surface, preventing liquid from getting to the surface of the tube, thereby decreasing boiling heat transfer coefficients, this was compensated for by an increase in condensation heat transfer coefficients as the inclination angle increased as a result of accelerated condensate liquid film in the tube. Thus, the overall effect of inclination angle on the thermal performance of a single-tube pool heat exchanger is inconsequential. 1. Introduction Pool heat exchangers are important elements of advanced passive thermal–hydraulic safety systems for most advanced nuclear power reactors. For example, in the Advanced Power Reactor Plus (APR+), the pool heat exchanger is associated with a passive condensation cooling tank (PCCT) and passive auxiliary feed water systems (PAFS) in which the decay heat is removed from the reactor core by cooling down the secondary system of the steam generator using a condensation heat exchanger installed in the PCCT, as reported by Yoon et al. (2014). Pool heat exchangers are also associated with passive residual heat removal (PRHR) systems, isolation condenser systems (ICS), and passive con- tainment cooling systems (PCCS), as described by Cummins et al. (2003). Heat exchanger tubes used in such passive safety systems of ad- vanced nuclear reactors have diverse orientations. Various shapes and configurations of pool heat exchangers are illustrated in Fig. 1. No re- presentation of scale was intended in these drawings, and no attempt was made to represent the bundle configuration of the condenser tubes. Features to note in the drawings are that: (1) a PRHR has both hor- izontal and vertical runs in the heat exchanger tubes, (2) a PAFS has slightly inclined (∼3°) runs in the heat exchanger tubes, and (3) ICS and PCCS have vertical runs in the heat exchanger tubes. The key safety issue associated with the pool heat exchangers is their capability to remove thermal energy from the reactor at the rate at which it is being added. However, the effects of the orientation of these pool heat ex- changers on their heat removal capabilities have not been investigated systematically. A brief investigation reported by Minocha et al. (2016) http://dx.doi.org/10.1016/j.nucengdes.2017.08.014 Received 13 February 2017; Received in revised form 3 August 2017; Accepted 14 August 2017 ⁎ Corresponding author at: Department of Nuclear Engineering, Kyung Hee University, Yongin 446-701, Republic of Korea. E-mail address: hdkims@khu.ac.kr (H. Kim). Nuclear Engineering and Design 323 (2017) 142–155 Available online 30 August 2017 0029-5493/ © 2017 Elsevier B.V. All rights reserved. MARK