Analysis of prediction methods for non-equilibrium internal flow condensation heat transfer

Abstract

Due to the climate crisis, there is a need to improve the performance of energy conversion systems and increase the use of renewable energy sources. In this context, accurate performance prediction methods for heat exchangers, including condensers, are of crucial importance. In the heat transfer process in a condenser including desuperheating and subcooling, both sensible and latent heat transfer may occur simultaneously due to thermal non-equilibrium effects. Liquid condensate may form close to the vapor saturation point of the bulk flow in the desuperheating region, while superheated vapor may penetrate beyond the liquid saturation point far into the two-phase region, and gas bubbles and subcooled mixture may exist in the subcooled region. These are complex phenomena that to a large extent affect the performance of the condenser. This paper presents an analysis of the prediction methods for non-equilibrium condensation heat transfer. First, the heat transfer mechanisms of non-equilibrium condensation are discussed. Next, state-of-the-art prediction methods developed for the target heat transfer processes are analyzed. Moreover, a database containing all data available in the open literature is built to evaluate the predictive performance of the prediction methods. Finally, a new prediction method is proposed for the subcooled condensation based on the identified heat transfer mechanisms. The results suggest that the Jacob correlation has the best predictive performance, followed by the Kondou correlation. The mean absolute percentage errors of both the Jacob and Kondou prediction methods are lower than 15 %, and more than 85 % of the experimental data points are predicted with a deviation within ± 30 %. The new prediction method proposed for the subcooled condensation is in good agreement with the experimental data, with a mean absolute percentage error of 12 %.