Theory About The Application Of Rapid Expansion

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Preparation of ultrafine particles active material, there is the traditional method has some limitations. For example, some degradation of biological products should not be easy to smash a way to change the use of their particle size and distribution of the state; and Gas Preparation of ultrafine particles, either physical or chemical vapor gas law, are accompanied by a large number of heat the occurrence of spray is operated under high temperature, biological active substances generally have heat-sensitive, easily decomposed at high temperatures, deactivation.

This technology has been in China on a number of research and application, reducing the particle size, particle morphology of such control has been success, such as Zhao-Hui Wang developed a Rapid Expansion of use of aluminum particles in isopropyl alcohol test equipment. The rapid expansion of technology has been around 1μm fine particle. Chen use this method to the effective pharmacological Po Shi Gee composition made of α-abalone a diameter of 2.1-18.5μm of fine particles.

Rapid Expansion of experimental studies have been largely focused ...
... on technology or other parameters on the product characteristics; such as changing the extraction pressure, solute concentration, expansion before the pressure, temperature and nozzle size change on the size of crystalline particles, thereby provide the basis for theoretical study and as a basis for industrial scale.The process of rapid expansion nozzle is a key component, studies on the flow of the process is carried out around the nozzle. Matosn will be rapid expansion of SCF in the expansion process is divided into three distinct phases: the first in the nozzle expansion occurred within the length of the process is similar to the process area and the subsonic adiabatic expansion; second stage supersonic free expansion process is isentropic area; third stage is the expansion of the area around the gas jet and interaction. Based on the experiments in recent years, the establishment of a one-dimensional was compressible flow model. Berned studied the crystal of benzoic acid and the Philippines in the crystallization from the supercritical CO2 and growth results; the flow of fluid in the nozzle is approximately one-dimensional adiabatic flow with friction. East China University of Hong-Yan Chen in the above flow model based on the combination of convective heat created Rapid Expansion of Supercritical flow calculation model. The model wills RESS process flow within the nozzle is divided into one-dimensional isentropic throttle and steady compressible pipe flow of two parts, and calculated. Most of professor studied the heat transfer fluid nozzle wall and the fluid flow of the nozzle and the nozzle exit parameters. Throttling process through the calculation, the process can get the temperature of fluid flow, pressure distribution.

In the crystallization theory, Tvanaa and RnadoPlh through a batch crystallization process of supercritical CO2 in the crystallization mechanism of acid into the nucleus through the research identified the different cooling and decompression process on the crystal size effects, confirming the concept of crystal nucleation and growth of the correctness. Tai and cheng by studying the Philippines in supercritical CO2 in the mechanism and kinetics of growth, they believe that the growth mechanism of the Philippines and dynamics in liquid solution with similar, but different in the gas phase growth.

Thermodynamics of the process, the general view that, for dilute supercritical solution, the critical parameters of pure solvents with a small difference changes the phase behavior of the expanding process of the thermodynamic diagrams by solvent, such as the enthalpy - entropy - to determine the pressure map.

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