Heat transfer enhancement of paraffin wax using compressed expanded natural graphite for thermal energy storage

Compressed expanded natural graphite (CENG) matrices with different densities were used to increase the thermal property of paraffin wax. To predict the performance of the paraffin wax/CENG composites as a thermal energy storage system, their structure, thermal conductivity and latent heat were characterized. Results indicated that the thermal conductivity of the composites can be 28-180x that of the pure paraffin wax. The existence of natural convection can reduce the time necessary for melting due to the anisotropy of the pore structure and thermal conductivity in CENG matrix. There are almost linear relationships between the thermal conductivity and the bulk density of the CENG matrix, and between the latent heat of the composite and the mass ratio of paraffin wax in the CENG matrix. (C) 2009 Elsevier Ltd. All rights reserved.