Session: 13-01: Computer Code V&V - I

Paper Number: 134262

134262 - Modeling Co-Current and Counter-Current Flow: A Performance Evaluation of the Trace Condensation Model With Non-Condensable and Light Gases 

Abstract: 

Modeling Co-Current and Counter-Current Flow: A Performance Evaluation of the TRACE Condensation Model with Non-Condensable and Light Gases

Abstract: Ensuring the effective condensation of steam is crucial for the safe and efficient operation of Nuclear Power Plants (NPPs), whether they are functioning under normal conditions or facing unforeseen circumstances. This is essential for mitigating the risks associated with excessive pressure and overheating. However, the presence of Non-Condensable Gases (NCGs) can hinder the condensation process by creating a thermal resistance layer, obstructing steam diffusion, and impeding condensation on the system's surface. Hence, this research aims to enhance our understanding of the steam condensation process by validating and assessing its performance in the presence of non-condensable and lightweight gases. To do so, the study makes use of a condensation setup situated in the vertical tube of KAIST's Passive Containment Cooling System (PCCS) facility. This facility is chosen for its accessibility in the context of validation. Going beyond previous validations with RELAP5/MOD3.2, which concentrated on pure steam and air, this research incorporates TRACE validation to investigate the impact of non-condensable and lightweight gases—specifically, Air, Nitrogen, Hydrogen, and Helium. The study generates various scenarios, mapping them to TRACE parameters to comprehend the influence of these gases. Utilizing the user-friendly SNAP graphical interface, a geometric model is constructed and subsequently verified within the TRACE code, showcasing satisfactory alignment with experimental data. Following this, 2,100 TRACE cases are generated to assess the Condensation Heat Transfer Coefficient (HTC). Based on these data points, Pearson correlation coefficients suggest that the mass fraction exerts the most significant detrimental influence on the HTC, closely followed by the gas type determined by molecular weight. Given the pronounced negative impact of mass fraction and molecular weight on the condensation HTC, the initial focus is on their influence on liquid generation rate in co-current flow condensation. Results show that increasing mass fraction and molecular weight decrease the liquid generation rate compared to pure steam. Investigation of mass fraction and molecular weight impact on drain mass flow rate in steam/NCG mixture flow variations reveals their role in initiating counter-current flow limitations (CCFL). Findings indicate that reaching the NCG mixture flow rate threshold halts condensation, marking the onset of CCFL. Additionally, increased mass fraction and switching to gases with higher molecular weights result in an earlier occurrence of CCFL.

Keywords: Condensation heat transfer coefficient, Co-current flow, Counter-current flow, Light gases, Non-condensable gases, Passive containment cooling systems, TRACE.

 

Presenting Author: Samah A. Albdour Khalifa University

Presenting Author Biography: Ms. Samah Albdour is in the last year of her Mechanical and Nuclear Engineering Ph.D. program at Khalifa University, working under the guidance of Dr. Afgan and Dr. Addad. She earned an MSc in Mechanical Engineering from Kyungpook National University in South Korea and a bachelor's degree in Nuclear Engineering from Jordan University of Science and Technology. Her doctoral research centers on modeling condensation processes in the presence of non-condensable gases within nuclear power plants.

Authors:

Samah A. Albdour Khalifa University
Yacine Addad Khalifa university
Imran Afgan Khalifa University