Fig. 3: Enhanced condensation heat transfer of F-DLC.

a Schematic of the chamber (not to scale) used for the condensation heat transfer experiments. Full details of the chamber and its operation can be found in Supplementary Notes 4a and 4b^54,55. The Cu tube sample having outer diameter D_OD = 9.53 mm, inner diameter D_ID = 8.0 mm, and length L = 134.6 mm was cooled via chilled water flowing inside of the tube at 8 ± 0.2 L min⁻¹. b Optical images during condensation showing (top) dropwise condensation on the F-DLC coated smooth Cu tube, and (bottom) filmwise condensation on the smooth uncoated hydrophilic Cu tube. The chamber vapor pressure P_v = 2.67 ± 0.15 kPa was identical for both tests. c Experimentally measured and theoretically computed steady-state condensation heat transfer coefficient (h_c) as a function of saturated steam vapor pressure (P_v) on the F-DLC coated Cu (dropwise) and bare Cu (filmwise) tubes. Error bars were computed using the propagation of error (see Supplementary Note 4c). The theoretical prediction for dropwise condensation (blue dotted line) was obtained using the classical droplet growth and distribution model (see Supplementary Note 4d). The theoretical prediction for filmwise condensation (red dotted line) was obtained using the Nusselt filmwise condensation model for a single horizontally oriented tube (see Supplementary Note 4e). For details about the experimental facility, test protocols, and uncertainty propagation, refer to Supplementary Notes 4a, 4b, and 4c.