Experimental investigation on supercooling, thermal conductivity and stability of nanofluid based composite phase change material

Abstract

With increasing concerns over global warming, there is compelling need to apply energy technologies to improve energy efficiencies. One of the new technologies is the use of phase change materials (PCMs) to store energy and release it on demand. However, most of these materials undergo supercooling, aggregation and have low thermal conductivity that inhibits effective heat transfer. In this paper supercooling, stability, energy storage,thermal conductivity and latent heat of fusion of water based nanofluid of barium chloride dehydrate (BaCl2·2H2O) were experimentally studied by adding a mass fraction of 0.2 w.t%–1 wt.% magnesium oxide (MgO) and 0.2 wt.%–1 wt.% multi-walled carbon nanotubes (MWCNTs). Results show that by adding separately mass fraction of 1.% of MgO and MWCNTs reduce the supercooling degree of barium chloride dehydrate by 85% and 92% respectively. At the same mass fraction, thermal conductivity also improves by 6% on addition of MWCNTs and 17% on addition of MgO. However, the enthalpies reduce by 7% at 1 wt.% MgO and by 12.3% at 1 wt% MWCNTs. It was found that MgO exhibited relatively higher thermal conductivity and a lower reduction in latent heats at a mass fraction of 1 wt.%. Surfactant was also found to prevent aggregation at low temperatures.