Prediction Method of Condensation Heat Transfer from Steam-Air Mixture for CFD Application

In our previous study, we measured the radial and axial temperature distributions of steam-air mixture in a vertical circular pipe (diameter, 49.5 mm; cooling height, 610 mm). The measured temperatures were used to evaluate the condensation heat flux qc and heat transfer coefficient hc, where the bulk quantities were defined at the center of the circular pipe. It is sometimes difficult to define the bulk quantities in a three-dimensional computation for a complex geometry or complex flow field. In this study, therefore, we evaluated a prediction method for hc without the definition of the bulk quantities by using the measured temperature distributions. We applied existing hc correlations to an arbitrary radial location y from the condensation surface, and obtained the distribution of local hc. As a result, we found that hc was radially almost constant in the turbulent boundary layer (dimensionless distance of y+ > 20). This means that existing hc correlations are applicable to computational cells of y+ > 40 in a three-dimensional computation.