Internal dropwise condensation: Modeling and experimental framework for horizontal tube condensers

Many researches have been focused on internal condensation with machined microstructure patterns on internal surfaces that can improve heat transfer performance up to 400% comparing to smooth surfaces. However, microstructure patterns are not effective for all geometries such as micro-channels and other complicated shapes. This study uses a dropwise condensation (DWC) promoter that can be easily applied to different geometries to improve internal condensation heat transfer. The main objectives of this study are to investigate internal condensation heat transfer by the dropwise condensation promoter via (i) developing an internal dropwise condensation model and (ii) conducting internal condensation experiments with the dropwise condensation promoter. The dropwise condensation model was modified to the available internal condensation model. The experiments for internal steam condensation were conducted for aluminum and copper tubes with external fins and an internal coating for dropwise condensation. The experimental results are compared to the results from several correlations in the literature and the model developed in this study. It is found that most correlations in the literature overestimate internal condensation heat transfer coefficients at low mass fluxes. The dropwise condensation model shows that dropwise condensation promoters can enhance internal condensation heat transfer coefficients. This conclusion is verified by experimental results demonstrating that the hydrophobic dropwise condensation promoter used in this study can enhance internal condensation heat transfer coefficients by 50%.