© 2015 Elsevier Ltd. All rights reserved. This paper investigated natural convection and nucleate boiling of PF-5060 dielectric liquid on 10 × 10 mm uniformly heated copper (Cu) surfaces with different diameter dimples, for potential application to immersion cooling of high power computer chips. The circular dimples, 300, 400, and 500 μm in diameter and 200 μm deep, have a triangular lattice with a pitch-to-diameter ratio of 2.0. The total number of dimples on the 10 × 10 mm surfaces increases with decreasing the dimple diameter. In addition to the dimple diameter, the performed experiments quantified the effects of the surface inclination angle and the liquid subcooling on the nucleate boiling heat transfer coefficient, hNB, and the critical heat flux (CHF). The inclination angle varied from 0° (upward facing) to 180° (downward facing) in increments of 30°, and the liquid subcooling includes 0 K (saturation), 10 K, 20 K and 30 K. In the upward facing orientation, the Cu surface with 400 μm dimples gives the highest hMNB (∼1.06 W/cm2 K) and CHF (∼19.3 W/cm2). The values for the surface with 500 μm dimples are ∼1.0 W/cm2 K and ∼18.7 W/cm2, respectively, and ∼0.7 W/cm2 K and ∼18 W/cm2 on the surface with 300 μm dimples. The CHF and hMNB on all dimpled Cu surfaces decrease with increased inclination angle to the lowest values in the downward facing orientation. These values are ∼36% and ∼33% of those in the upward facing orientation, respectively. In addition, the CHF in the upward facing orientation, increases linearly with increased liquid subcooling at a rate of 1.8%/K.