In this experimental study, melting behavior of paraffin in a storage unit of the horizontal shell-and-tube type is investigated. In order to enhance melting rate, a conducting fin is attached to the bottom of the inner tube. At first, the tube without a fin is tested. Then, the tubes with fin of four different heights (h=10, 20, 30 and 40 mm) are examined. Experiments are conducted at constant values of the inlet temperature and the inlet mass flow rate of the heat transfer fluid (HTF). As phase change material (PCM), paraffin (solidification range of 56-58 C) is used. For each case tested, transient variations of the temperature at some specific radial points inside the phase change material (PCM) are obtained. For the case without a fin, natural convection recirculation is shown to be weak in the lower half region of the annulus when compared to that in the upper half region. Results show that attaching a conducting fin to the bottom of the inner tube intensifies the recirculation of liquid PCM in the lower half and, in follows, enhances the melting rate about 72.8% for the fin height of 40 mm when compared to without fin (h=0 mm).