Improvement Of Freezing Concentration Equipment And Micro-simulation In The Growth Of Ice Crystals

Freezing concentration as a non-thermal processing technologies, it is able to maximize the retention of the original fresh flavor of food and nutrition, the minimal changes in the Loss of volatile aromatic components and heat-sensitive components Of enzymes, color ,its unique advantages, will become the study of food processing technology, one of the hot spots. However, due to freeze concentration of ice crystals have a relatively high rate of entrainment, and it is difficult to be separated from the solution .The frozen concentrate that no appropriate equipment,its promotion and use is limited. Since a long time, in order to address the issue of entrainment of ice crystals, the unit size of ice crystals was concerned by domestic and foreign experts and scholars who con- trolled the growth of ice crystals based on the measured datas or main experience.This paper, the development of an appropriate frozen concentrated equipment used in laboratory . Through domestic and international field of metal micro-structure of the phase-field model, the law of formation of ice crystals and methods of controlling were explored. Specific research work and the main con- clusions were as follows:(1)Design a freeze concentration equipmentused in laboratory,crystallizer can be combined with the growth of pot that reduce the contamination,the remove ice methods can effective implementation of the separation of the size of ice crystals.(2)Design a freeze concentration equipmentused in laboratory,crystallization can be combined with the growth of pot that reduce the contamination,the remove ice methods can effective implementation of the separation of the size of ice crystals.(3)Watermelon juice for the experimental material Changes from 9(brix) to 46.6(brix). Watermelon juice in the enrichment process, Pre-loss rate of fruit juice is much larger than the late loss rate .its first 2 ~ 8 hours ,the loss rate of ice crystals in soluble solids reach to 71.8%,from 9～15h the loss rate of ice crystals in soluble solids reach to 27.1%, As a result, in the pre-freezing concentration , large temperature difference, ice crysta amount is large; in the later period ,small temperature differences ice crysta amount is small. (4) Obtain the heat transfer coefficient K=0.195kJ/(m2·s). Laboratory is going to build a set of medium equipment for freezing concentration, the K Can be used as the basis for the design of the crystallizer.(5)Ice crystal was a typical kind of solidfication structure. The phase-field model was introduced because of its non-equilibrium from its typical structure,involving energy,quality and momentum transfer,as well as the interface kinetics and the problem caused by capillarity effects coupled with the free boundary. Taken advantages of phase-field model which could change the sharp interface from the course of interface evolution into the diffuse interface, it was used to simulate the process of evolution of microstructure in the process of ice crystal growing of freeze concentration. The basic principles of phase-field,the discrete numerical solution, stability conditions, initial conditions and boundary conditions were discussed.(6)The growth process of ice crystals of supercooling water was numerically simulated by phase-field model, which including the course of evolution of ice crystal morphology at different cooling time, different degrees of supercooling.