Investigation of enhancement in the thermal response of phase change materials through nano powders

Abstract

A major problem faced by Phase Change Materials (PCM) based latent heat thermal energy storage systems is the slow thermal response. In this study, the feasibility of nano phase change materials composites is investigated experimentally by using various types of nanoparticles in PCM, to improve thermal response by increasing the thermal conductivity. Heat transfer enhancement of PCM composites (RT26 and coconut oil) is achieved by acquiring better thermophysical properties through seeding nanoparticles in PCM. RT26 and coconut oil are beneficial due to the absence of corrosion to metallic containers. A thermal response investigation is conducted with a flat slab type latent heat thermal energy storage unit. It was observed that the increase in thermal conductivity of PCM by seeding nanoparticles is useful for the improvement of heat transfer. Carbon nanotubes have shown better performance as compared to Al2O3 and Fe3O4 nanoparticles. It was further analyzed that at a 1 wt percent concentration of nanoparticles, the maximum heat transfer enhancement in RT26 caused by Fe3O4, Al2O3 and carbon nanotubes nanocomposites is up to 20.01, 36.68 and 64.21% respectively. The maximum heat transfer enhancement in coconut oil caused by Fe3O4, Al2O3 and carbon nanotubes nanocomposites is up to 8.83, 14.84 and 33.38% respectively. Therefore, it is revealed that RT26 has more potential for heat transfer enhancement as compared to coconut oil. This is due to the percentage improvement in the thermophysical response of RT26 as compared to coconut oil. The economic and environmental analysis was conducted to compare the performance of latent heat thermal energy storage unit with and without the application of nanoparticles in PCM, to estimate the most viable candidate among various nano composites. The economic analysis presented the lowest annual energy running cost and Net Present Value(NPV) for nanocomposite of carbon nanotubes in RT26 is Rs.-4381 and RS.-36375 respectively. Whereas the maximum annual energy cost and NPV for pure RT26 are Rs.-12240 and Rs. -75548 respectively. The NPV for Fe3O4 and Al2O3 is Rs.-62207 and Rs.-53062 respectively. The cost and NPV were Rs.-6646 and Rs.-55226 in the case of carbon nanotubes in coconut oil. It shows that the trend is the same in the case of Fe3O4 and Al2O3 nanoparticles in both RT26 and coconut oil, unlike of carbon nanotubes. The environmental analysis shows that the maximum and minimum payments of carbon dioxide by carbon nanotubes and Fe3O4 nano composites respectively in RT26, are Rs.7000 and Rs.2176. While the corresponding values are Rs.2975 and Rs.798 in the case of coconut oil. Hence, carbon nanotubes in RT26 have the highest economic and environmental viability. Accordingly, the enhancement in heat transfer using these nanoparticles will be helpful in air conditioning applications like animal houses.