Recently, latent heat thermal energy storage system has gained attentions in order to utilize the middle temperature factory waste heat (100-200 degrees C). The purpose of this study is to develop heat storage system with a latent heat storage material for using the middle temperature heat. In this study, the direct contact melting and solidification behavior between heat transfer fluid (oil) and erythritol (PCM) were visualized in order to investigate the characteristics of heat storage and release at difference flow rate of oil (1.0-4.0 kg/min) and the effects of perforated partition plate. In this direct contact method, if the packed height of erythritol increases due to porous solidification, erythritol may be flowed out from a vessel with oil. So to control the packed erythritol height, the effect of a perforated partition plate in the vessel was investigated. As a result, it is found that since the bubbles of PCM are broken by the perforated partition plate, it prevents that the solidified height of PCM increases. (C) 2014 Elsevier Ltd. All rights reserved.