Experiments are conducted to investigate nucleate boiling of HFE-7100 liquid on 10 × 10 mm copper surfaces with corner pins that are 3 × 3 mm in cross section and 2-, 3-, and 5-mm tall. Heat transfer coefficient and critical heat flux are compared for 0 (saturation), 10, 20, and 30Ksubcooling at orientations from θ = 0 to 180 deg. Thermal power removed in nucleate boiling at all orientations increases, partially due to the increase in surface area for boiling and the increased mixing by departing bubbles from the plane portion of the surface and sides of the pins. Increasing subcooling and pin height increases the thermal power removed and the temperature of the base surface. With 30 K subcooling, thermal power removed at critical heat flux from the copper surface with 5 mm pins at θ = 0 deg is in excess of 93 W, decreasing to 86W at θ = 180 deg. The corresponding base temperature is ̃91 and 95°C, compared with the saturation temperature in the experiments of ̃54°C. Critical heat flux increases linearly with increased liquid subcooling, and the developed correlation, which accounts for the effects of liquid subcooling and surface orientation and area in contact with the boiling liquid, is within +10%of data. © 2008 by the American Institute of Aeronautics and Astronautics, Inc.