Air-Side Heat Transfer and Friction Correlations for Schwarz-D Fin Condensers

Abstract The aim of the present study is to propose a new correlation to predict the j and f factors for the air-side of flat plate condensers made of triply periodic minimal surfaces (TPMS) fins of the Schwarz-D type. A total of 101 prototypes were tested, generating a database of 141 data points, with various geometrical parameters and operating conditions. In particular, fin gaps from 1.51 to 7.1 mm and flow lengths from 51 to 134 mm were investigated, with Reynolds numbers varying between 194 and 2624 for some test objects. The nonlinear least-squares Marquardt–Levenberg algorithm was used to develop a correlation including the Reynolds number, the fin curvature, the condenser aspect ratio, and the shearing angle. This correlation predicts 94% and 89% within a ±25% error band, of the measured f and j factors, respectively.