Analysis of the enhancing mechanism in pool boiling heat transfer through wetting speed for rough aluminum surfaces with FC-72

This study focused on the critical heat flux (CHF) characteristics in pool boiling heat transfer for various rough surfaces with FC-72. In particular, the enhancing effect of the CHF according to the direction of roughness was verified. Random rough surfaces with various roughness range were fabricated by the polishing process, and a unidirectional rough surface (URS) with hairlines on the surface was prepared for comparison. We proposed a CHF prediction model to analyze the enhancement of CHF on rough surfaces. The proportional relationship between the increase in CHF and the difference between the areal wetting speed on a rough surface and on a smooth surface was verified. The experimental CHF data were located in the median range of the proposed model, which was defined using the range of the Taylor instability wavelength in the Zuber model. In addition, the proposed model can predict the CHF for URS sample using the average of the areal wetting speed in both parallel and normal directions. (C) 2020 Elsevier Ltd. All rights reserved.