A rotating heat pipe assembly was tested at rotational speeds of 700, 1400, and 2800 rpm using distilled water as the working fluid. Tests were made during film condensation on several copper condensers, including smoothwalled cylinders, an internally finned cylinder, and a truncated cone. The truncated cone surface was also promoted for dropwise condensation using n-octadecyl mercaptan in octanoic acid. Heat-transfer performance improved with increasing rotational speed. The internally finned cylinder and the truncated cone showed a 100% improvement over the equivalent smooth-walled cylinder. Dropwise condensation showed substantial improvement over film condensation, primarily at low rotational speeds. Nomenclature cp = specific heat gc = gravitational constant m = mass rate of flow Q = heat-transfer rate R = radius AT = cooling water temperature difference p = density a = surface tension o> = angular velocity