The major technical issue in gas hydrates energy storage systems is how to increase the refrigerants-water mass and heat transfer and how to realize a rapid formation of clathrate hydrate. Borrowing ideas from heat transfer enhancement of the fluid with the addition of nano-sized particles, the formation and dissociation of HFC134a (CH2FCF3) hydrate were studied in nano-copper suspensions of different mass fractions. The experimental results indicate that the addition of nano-copper enhances the heat and mass transfer process of HFC134a hydrate formation, which was shortened with the increasing mass fraction of nano-copper. Compared with the dissociation pressure at a given temperature below the critical dissociation point, a significant upward shift of the dissociation pressure of the HFC134a. hydrate formed in the nano-fluid was observed. The critical dissociation point shifts from the former point (283.15 K, 414.86 kPa) to the latter one (282.65 K, 401.35 kPa.), and the dissociation curve does not shift with the change of mass fraction of the nano-copper. (c) 2005 Elsevier Ltd. All rights reserved.