Experimental study was carried out to study the phase change heat transfer within a composite of phase change material ͑PCM͒ infiltrated high thermal conductivity foam. An experimental setup was built to measure the temperature profiles and capture the melting evolution of the PCM inside aluminum foams. Aluminum foams were used as the porous material, and low melting temperature paraffin wax was used as the PCM. It was observed from the results that the system parameters of the wax/foam composite had a significant influence on its heat transfer behavior. By using higher porosity aluminum foam, the steady-state temperature was reached faster as compared to the foams with lower porosity. Similarly for the bigger pore size foams the steady state was attained faster as compared to the smaller pore size foams. This was due to the greater effect of convection in both the higher porosity and bigger pore size foams. However, for the lower porosity foams the heater temperature was comparatively lower than the higher porosity foams due to greater heat conduction through the foam material. Therefore, an optimal value should be selected for the foam porosity and pore size such that the effects of both conduction and convection heat transfers can be completely utilized to have a greater and improved thermal performance for the wax/aluminum foam composite.

Latent energy storage capacity was analyzed for a system consisting of carbon nanoparticles doped phase change materials ͑PCMs͒. Three types of samples were prepared by doping shell wax with single wall carbon nanotubes ͑SWCNTs͒, multiwall CNTs, and carbon nanofibers. Differential scanning calorimetry was used to measure the latent heat of fusion. The measured values of latent heat for all the samples showed a good enhancement over the latent heat of pure wax. A maximum enhancement of approximately 13% was observed for the wax/SWCNT composite corresponding to 1% loading of SWCNT. The change in latent heat was modeled by using an approximation for the intermolecular attraction based on the Lennard-Jones potential. A theoretical model was formulated to estimate the overall latent energy of the samples with the variation in volume fraction of the nanoparticles. The predicted values of latent energy from the model showed good agreement with the experimental results. It was concluded that the higher molecular density of the SWCNT and its large surface area were the reasons behind the greater intermolecular attraction in the wax/SWCNT composite, which resulted in its enhanced latent energy. The novel approach used to predict the latent heat of fusion of the wax/nanoparticle composites has a particular significance for investigating the latent heat of PCM with different types of nanoparticle additives.

The present work involves a study on the thermal conductivity of nanoparticle-oil suspensions for three types of nanoparticles, namely, carbon nanotubes ͑CNTs͒, exfoliated graphite ͑EXG͒, and heat treated nanofibers ͑HTT͒ with PAO oil as the base fluid. To accomplish the above task, an experimental analysis is performed using a modern light flash technique ͑LFA 447͒ for measuring the thermal conductivity of the three types of nanofluids, for different loading of nanoparticles. The experimental results show a similar trend as observed in literature for nanofluids with a maximum enhancement of approximately 161% obtained for the CNT-PAO oil suspension. The overall percent enhancements for different volume fractions of the nanoparticles are highest for the CNT-based nanofluid, followed by the EXG and the HTT. The findings from this study for the three different types of carbon nanoparticles can have great potential in the field of thermal management.

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