Development of a Prototypical Condensation Model for the Nearly Horizontal Heat Exchanger Tube of the APR+ PAFS (Passive Auxiliary Feed-water System)

摘要

A new condensation heat transfer model based on the flow regime in the nearly horizontal tube has been developed for the Passive Auxiliary Feed-water System (PAFS) of Korean Advanced Power Reactor Plus (APR+). This study focused on the stratified flow in horizontal pipes in which two different heat transfer mechanisms are involved. The void fraction was determined from the 1-D separated flow model (SFM) which incorporates closure relations for shear stress defined by single-phase based expressions and geometric relations for a concave interface using the eccentric circles. The wetted angle proposed by Hart correlation (1989) was used to classify flow regimes into annular, stratified-wavy and stratified-smooth flow. The new film condensation heat transfer correlation based on Nusselt integral analysis (1916) was proposed to predict the heat transfer coefficient affected by the vapor flow on the upper portion of tube in the stratified flow. Furthermore, the convective heat transfer correlation for single-phase heat transfer was used to predict the heat transfer coefficient for condensate flowing on the entire perimeter of annular flow and the bottom of the stratified flow. Finally, the new condensation heat transfer model package was evaluated against available experimental data for water and it shows good results.