Solidification characteristics of paraffin in a horizontal shell-and-tube type-storage system are investigated experimentally. The inlet temperature and the mass flow rate of the heat transfer fluid (HTF) are kept constant. Eccentric geometries for the storage system in which inner tube center is vertically aligned eccentric with the center of the outer shell as well as the concentric geometry are tested. Five different values of the eccentricity from the center of the outer shell are considered: e = -10, -20, -30,10,20, and 30 mm besides the concentric geometry (e = 0). The focus of the study is on understanding the solidification behavior based on the transient temperature fields inside PCM. Eccentricity is shown to affect the total solidification time considerably. With an increasing eccentricity of the HTF tube (i.e. the inner tube), either upward or downward from the center of the outer shell, the total solidification time increases. (C) 2013 Elsevier Ltd. All rights reserved.