Cu nanoparticles were added into the deionized water with dispersant and ultrasonic wave to prepare the dispersive Cu-H2O nano fluid. The effect of nano fluid on the characteristics of vacuum flash ice preparation by changing the particle size and the mass fraction of nano fluid under the 100 Pa was explored experimentally. As the results showed

adding nano particles into water without dispersant (nano particles have settling phenomenon)

can reduce the supercooling degree of water

and shorten the time of phase change. However the uniform dispersion of nano fluid without settlement can significantly shorten the time of phase change

and the supercooling degree is reduced by 37%. At the initial flash moment

nano fluid has little effect on the cooling process of liquid phase. The larger the mass fraction of the nano fluid

the shorter the icing time

and the greater the cooling rate of the solid phase. The phase transformation time is shortened with the decrease of the particle size

but the temperature drop rate is almost the same in the solid phase. The change of particle size has little effect on the supercooling degree of the solution

which is basically maintained at 1.5℃ at lower concentration.