This paper presents an experimental study on heat transfer characteristics of PCMs embedded in open-cell metal foams and expanded graphite, respectively. In this study the paraffin wax RT 27 and calcium chloride hexahydrate are employed as the heat storage media and the transient heat transfer behavior is measured. The results indicate that the addition of porous materials, either open-cell metal foams or expanded graphite, can enhance the heat transfer rate of PCMs. Especially for metal foams, the results show that they can double the overall heat transfer rate during the melting processes. The effect of mass ratio of expanded graphite on heat transfer is examined. (C) 2010 Elsevier Ltd. All rights reserved.