Research Thrust IV
Phase-Change-Material Nanoemulsions for Energy Transport and Storage
Highly stable nanoemulsions of a phase change material (PCM) such as tetradecane and beeswax in water have been developed using common surfactants and a low energy emulsification method by CCNY and IRSTEA researchers. However, their rheological and heat transfer characteristics must be studied extensively to utilize them in practical thermal energy storage systems. Nanoemulsions with a mean particle size of ~200 nm have been shown to be stable with no significant phase separation for more than one year. Emulsion viscosity increases significantly when the solid fraction exceeds 10%, which is much lower than in ice slurries. Further investigations are necessary to obtain lower viscosities at higher solid fractions to achieve a greater thermal storage capacity. In forced convection experiments, thermal non-equilibrium effects and unusual instabilities (large amplitude oscillations in the flow rate and heated tube surface temperatures) have been observed at the phase change temperature in both nanoemulsions and gas hydrate slurries.
Thus, the formation, stability and transport phenomena in PCM nanoemulsions will be experimentally and computationally investigated. The effects of nucleation agents on supercooling phenomena will be investigated by differential scanning calorimetry (DSC), and rheological properties will be determined as a function of temperature. An X-ray imaging system will be used to investigate the agglomeration and formation of particle clusters as well as solid fraction distributions in heated flow channels. Multi-dimensional NMR will be used to characterize the molecular compositions and structures of the nanoemulsion phases and their interactions with adsorbed species. These studies will be conducted in collaboration with French researchers since there are many common multi-scale, multiphase phenomena of interest in both hydrate slurries and PCM nanoemulsions.
CCNY: Masahiro Kawaji, Robert Messinger, Artur Zych
Fraunhofer ISE: Stefan Gschwander, Peter Schossig
IRSTEA: Anthony Delahaye, Laurence Fournaison
ENSTA ParisTech: Didier Dalmazzone
INP-LGC: Olivier Masbernat
IPF: Ulrich Scheler