This research paper specifically focuses on experimentally characterizing and elaborating the effect of z-aligned carbon nanofibers (CNFs) on the through-thickness (i.e., z-direction) thermal conductivity of paraffin wax. The z-aligned CNF network present within the paraffin sample was hypothesized to provide a thermally-conductive nanostructure throughout the sample thickness, thereby increasing the thermal conductivity and the thermal energy charging/discharging capabilities of the paraffin wax. It was further hypothesized that the effectiveness of this thermally-conductive nanostructure was strongly related to both CNF alignment and CNF concentration.
To experimentally analyze the respective impact of CNF concentration (measured as a percentage of sample weight) and CNF alignment on the through-thickness thermal conductivity, z-aligned CNF-modified paraffin wax samples with various CNF concentrations were manufactured and compared with unmodified (i.e. control) paraffin wax samples and unaligned CNF-modified paraffin wax samples; the concentration of CNF-reinforcement was tested at both 0.1wt.% and 0.3wt.%. The through-thickness thermal conductivities were characterized for all samples using a steady-state parallel plate testing device and the results were compared and discussed against the experimental parameters. It was found that both CNF alignment and concentration had a strong influence on the improvement of through-thickness thermal conductivity of paraffin wax.