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A computational analysis of the effects of the input process parameters on the final product properties in the spray dryer for tannin particles

其他書名	master thesis
出版	B. Krajnc, 2009
URL	http://books.google.com.hk/books?id=-DcWMwEACAAJ&hl=&source=gbs_api

註釋The design of spray dryers is typically optimized for the unique operating conditions. How-ever, users sometimes need to use the same spray dryer chamberwith some modifications due to the requirements of different products and/or production rates. Additionally, modification of operating conditions isvery often used in order to improve thermal efficiency of the overall spray drying process. In this work results of a computational fluid dynamic (CFD) analysis of the effects of in-put process parameters on final product properties in the spray dryer for tannin particles are presented. Commercial CFD code ANSYS CFX 11.0 SP1 and spray dryer model template supplied with have been used. Model template has been modified and utilized (a) for simple hexahedral spray dryer of tannin water mixture in order to initially analyze the behaviour of the model, and (b) for reference lab-scale spray dryer of both maltodextrin water mixture in order to validate the model by comparison to Huang et al. (2006) and tannin water mixture in order to analyze the effectof decreased inlet temperature of drying air. Results of steady state simple spray dryer simulations are presented. Particle trajecto-ries are presented that reveal intensive droplet evaporation for high inlet temperatureof drying air and only poor volatilization accompanied with dropletcooling for inlet tempera-ture being too low. Transient reference spraydryer simulations have been performed for two different mesh sizes and particle rates for maltodextrin mixture. Presented time averaged profiles at different levels in the drying chamber reveal reasonable matching of velocity profiles. Additional transient tannin mixture simulations for two different inlet temperatures reveal reasonable matching of temperature and humidity profiles too, yet for different initiali-zation and longer physical run time. Thus, a numerical model capable to handle full-scale industrial spray drying process has been built up, which has to be improved further, however.