Saturation pool boiling experiments of degassed PF-5060 dielectric liquid investigated nucleate boiling on 13 Cu surfaces with average roughness, Ra, of 0.039 (smooth polished) to 1.79 lm at six inclination angles, θ, from 0 deg (upward facing) to 180 deg (downward facing). Values of the nucleate boiling heat transfer coefficient, hNB, in the upward facing orientation increase with increasing surface roughness and are correlated in terms of the applied heat flux, q: hNB=A qB. The exponent \"B\" decreases from 0.81 to 0.69 as Ra increases from 0.039 to 1.79 μm, while the coefficient \"A\" increases with Ra to the power 0.24. The values of the maximum heat transfer coefficient, hMNB, which occurs near the end of the fully developed nucleate boiling region, increase with increasing Ra and decreasing inclination angle. In the upward facing orientation, h NB increases by ~58% with increasing Ra from 0.134 to 1.79 μm, while hMNB increases by more than 150% compared with that on smooth-polished Cu. Values of hMNB in the downward facing orientation are ~40% of those in the upward facing orientation. Copyright © 2014 by ASME.