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

Abstract

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 q_c and heat transfer coefficient h_c, 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 h_c without the definition of the bulk quantities by using the measured temperature distributions. We applied existing h_c correlations to an arbitrary radial location y from the condensation surface, and obtained the distribution of local h_c. As a result, we found that h_c was radially almost constant in the turbulent boundary layer (dimensionless distance of y⁺ > 20). This means that existing h_c correlations are applicable to computational cells of y⁺ > 40 in a three-dimensional computation.