Melting of an organic phase change material (PCM) n-triacontane (C30H62) in a side heated tall enclosure of aspect ratio 10, by a uniformly dissipating heat source has been studied computationally and experimentally. While heat transfer data for melting in enclosures under isothermal wall boundary condition are available in the literature, other boundary conditions, such as constant heat flux often arise in applications of PCM for transient thermal management of electronics. An implicit enthalpy-porosity approach was utilized for computational modeling of the melting process. Experimental visualization of melt front locations was performed. Comparisons between experimental and computational heat transfer data and melt interface locations were good. Fluid flow and heat transfer characteristics during melting suggested that natural convection plays a dominant role during initial stages of melting. At later times, the strength of natural convection diminishes as melting is completed. Correlations of heat transfer rate and melt fraction with time were obtained. (C) 2000 Elsevier Science Ltd. All rights reserved.