Highly conducting coreeshell phase change materials for thermal regulation Nuno Vitorino a , João C.C. Abrantes a, b, * , Jorge R. Frade a a Department of Materials and Ceramic Engineering, CICECO, University of Aveiro, 3810 Aveiro, Portugal b UIDM, ESTG, Polytechnic Institute of Viana do Castelo, 4900 Viana do Castelo, Portugal highlights graphical abstract  Coreeshell composite model for highly enhanced transport properties.  Self organized graphiteeparaffin composites for fast latent heat charge and discharge.  Cellular composites by emulsification of paraffin in aqueous suspensions. article info Article history: Received 9 September 2013 Accepted 2 February 2014 Available online 8 February 2014 Keywords: Microstructural design Self-assembling Coreeshell Phase change materials Thermal conductivity abstract A coreeshell model has been derived for microstructural design of PCM-based composites with opti- mized 3-dimensional organization of a conducting phase, and a novel method was developed to process self-assembled coreeshell composites for thermal regulation or heat storage. The method was based on emulsification of graphite suspensions in melted paraffin yielding a coreeshell microstructure based on self-organisation of graphite platelets with preferential orientation; this allows remarkable enhancement of thermal conductivity, which increases by at least one order of magnitude for 5 vol% graphite addition. The microstructure of the graphite shell remains stable upon repeated cycling above and below the melting temperature of the paraffin, and shape stabilization is also retained, even without external encapsulation. One confirm that the levels of thermal conductivity of these phase change materials is sufficient for latent heat discharge from relatively large spherical samples to surrounding air. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Phase change materials (PCM) are widely proposed for thermal management and heat or cold storage applications, based on the high latent heat. However, thermal conductivity is usually lower than 0.5 W m 1 K 1 [1] which sets kinetic limitations. In order to overcome these kinetic limitations a variety of strategies to increase the PCM thermal conductivity has been used [2e16]. Table 1 summarize some of these strategies, with emphasis on PCM- based composites with conducting metallic structures [4e6], PCM/carbon composites [8,9,17], and other less common compos- ites [10,16,18]. Though most of these approaches rely on highly conducting phase, for the sake of simplicity, this yields limited gains in thermal conductivity [4,8,11,13,17], even on adding highly conducting materials, such as nanostructured carbons [8,12e15,17]. High volume fractions of the highly conducting phase increase thermal conductivity but affect latent heat storage [7]. * Corresponding author. UIDM, ESTG, Polytechnic Institute of Viana do Castelo, 4900 Viana do Castelo, Portugal. Tel.: þ351 258 819 700; fax: þ351 258 827 636. E-mail address: jabrantes@estg.ipvc.pt (J.C.C. Abrantes). Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng http://dx.doi.org/10.1016/j.applthermaleng.2014.02.001 1359-4311/Ó 2014 Elsevier Ltd. All rights reserved. Applied Thermal Engineering 66 (2014) 131e139