Study of freezing characteristics of water based grapheme Nano-fluid PCM in a spherical capsule

Abstract

In the present scenario of increasing levels of energy consumption, a lot of research focus is being carried out in optimising thermal energy consumption. The latent heat energy storage system is widely being identified as a viable option which possesses very high potential to optimise thermal energy consumption in Refrigeration and Air-conditioning applications. The efficient functioning of a latent heat energy storage system mainly depends on the phase change material, the phenomenon of sub-cooling and total freezing time. This paper reports the results of comparative experimental study on the freezing characteristics of water based nano fluid PCM with grapheme nano-particles inside a spherical encapsulation made of different materials. Graphene as a nano-particle possesses large surface area which enhances the heat transfer characteristics of the PCM. The materials used for the spherical encapsulation were high density poly-ethylene (HDPE) polymer and copper metal. Experimental tests are thus carried out on each of these spheres at specific HTF temperatures of the evaporator for a concentration of 0.1 wt% concentration of graphene in the PCM. The experimental results indicated a significantly reduction in total freezing time in the capsule sphere made of copper as compared to the sphere made of HDPE at a fixed HTF temperature for 0.1% graphene. The results also showed the elimination of sub-cooling phenomena for both cases during the charging process.