Improvement of CUPID code for simulating filmwise steam condensation in the presence of noncondensable gases

Abstract

a b s t r a c tIn a nuclear reactor containment, wall condensation forms with noncondensable gases and their accumulation near the condensate film leads to a significant reduction in heat transfer. In the framework of nuclear reactor safety, the film condensation in the presence of noncondensable gases is of high relevance with regards to safety concerns as it is closely associated with peak pressure predictions for containment integrity and the performance of components installed for containment cooling in accident conditions. In the present study, CUPID code, which has been developed by KAERI for the analysis of transient twophase flows in nuclear reactor components, is improved for simulating film condensation in the presence of noncondensable gases. In order to evaluate the condensate heat transfer accurately in a large system using the two-fluid model, a mass diffusion model, a liquid film model, and a wall film condensation model were implemented into CUPID. For the condensation simulation, a wall function approach with a heat/mass transfer analogy was applied in order to save computational time without considerable refinement for the boundary layer. This paper presents the implemented wall film condensation model, and then introduces the simulation result using the improved CUPID for a conceptual condensation problem in a large system.

Steam Condensation Heat Transfer in the Presence of Noncondensable Gases (NCGs) in Nuclear Power Plants (NPPs): A Comprehensive Review of Fundamentals, Current Status, and Prospects for Future Research

“…The HMTD approach is particularly effective in predicting heat and mass transfer coefficients at interfaces and considers the influence of NCGs on the condensation process through mass transfer effects. It can be applied to various condensation scenarios involving different fluids, geometries, and pressure conditions [74]. However, the HMTD model does have some limitations.…”

Improvement of Condensation Model With the Presence of Non-Condensable Gas for Thermal-Hydraulic Analysis in Containment

“…Resolved boundary method or HMTA method with wall function is usually used to model steam condensation. Fine near-wall mesh resolution (dimensional length y + <1) is required for the former method, which requires a lot of computing resources; HMTA method with wall function can reduce requirements for mesh resolution to a certain degree (Ambrosini et al, 2014;Lee et al, 2015). The GASFLOW code uses HMTA method with wall function to model steam condensation in containment (Wang et al, 2018).…”