Abstract: According to the predigestion and analysis of the rapid expansion of a supercritical solution process, a flow model of a nozzle for superfine particles preparation is established． The description of the one-dimensional time-independent flow model includes a conical entrance segment, straight pipe and outlet segment for ultrasonic expansion till mach disk. The main parameters origin in the model and the basic mechanisms of calculating the solution are also presented. Based on the model of the RESS process, the simulation of flow state in each stage is realized and some data of parameters including temperature, pressure, density and velocity along the axis of the nozzle are presented. Some guidelines to optimize parameters are offered to achieve uniform superfine particles.

Key words: rapid expansion of supercritical solution, nozzle, flow model, superfine particles