In this study, melting behavior of paraffin in a horizontal shell-and-tube type-storage unit is experimentally studied. Both the concentric and eccentric orientations of the inner tube according the center of the outer shell are considered. Three different values for the eccentricity from the center of the outer shell is investigated: e = 10, 20 and 30 mm besides the concentric geometry (e = 0). For each geometric orientation, effect of the inlet temperature on the melting behavior is also obtained. A special attention is paid to understand the melting behavior based on the temporal variation of temperature field inside PCM. Eccentricity is shown to respond much well to the melting behavior and hence enhance melting behavior due to intensified natural convection intensity inside PCM. (C) 2014 Elsevier Ltd. All rights reserved.