This paper presents an experimental investigation of phase change material (PCM) melting in a transparent rectangular enclosure with and without horizontal partial fins. The enclosure was heated isothermally from one side while the other walls were thermally insulated. Experiments were performed with wall temperatures of 55, 60 and 70 degrees C (3.6 x 10(8) <= Ra <= 8.3 x 10(8)) for finned and unfinned enclosures. Visualization of the melting process and the temperature field were performed directly. Both qualitative and quantitative information about the melting phenomena were obtained using digital photographs of the instantaneous melt front evolutions and temperature recordings at the vertical mid-plane of the enclosure. Temperature histories revealed that the thermally stratified region became smaller as the number of fins increased. Experimental data were used to calculate melt fractions, heat transfer rates and Nusselt numbers during the melting process. Furthermore, two correlation equations were developed using the dimensionless parameters to predict the Nusselt number and melt fraction. Also, in order to evaluate the improved thermal performance of the enclosure in the presence of partial fins, two other parameters were defined, melting enhancement ratio and overall fin effectiveness. Experimental results indicated that increasing the number of fins decreased the melting time and increased the total heat transfer rate while the surface-averaged Nusselt number reduced. Melting enhancement ratio and overall fin effectiveness increased with increasing the number of fins and decreased with raising the wall temperature. Melting enhancement ratios decreased with time after reaching some maximum values indicating that partial fins are more beneficial during the initial time of the melting. (c) 2014 Elsevier Ltd. All rights reserved.