This investigation pertains to the nucleate pool boiling heat transfer studies on submerged horizontal flat copper surfaces of different roughness at atmospheric and sub-atmospheric pressures. The experiments were carried out for distilled water and sodium chloride solutions (35,000 and 50,000 ppm) in the pressure range 10-100 kN/m2. The experimental results were compared with Rohsenow's correlation. The experimental boiling curve slope was lower than the Rohsenow's correlation. © 1985.