| Gravure printing is widely used in food,pharmaceutical,and other packaging industries.As a green printing material,water-based ink has problems such as non-volatility and poor drying on non-absorbent packaging substrates,which have a great limitation on its application.To solve these problems,this paper conducts a macroscopic and microscopic numerical simulation of hot air drying of gravure printing water-based inks through computational fluid dynamics(CFD)for the prediction of gravure printing water-based hot air drying inks.This approach can improve the drying efficiency of water-based inks,save process costs,and thus expand the application of waterbased inks on non-absorbent substrates.Firstly,this study establishes the geometric model of the drying oven based on the actual structure of the gravure oven for the fluid dynamic analysis of gravure drying by simplification.Then the local structure optimization is carried out by adding the deflector plate in the drying oven to study the influence of the structure of the deflector plate on the hot air drying effect of gravure water-based ink,which can assist the structural design of the gravure drying oven and improve the uniformity of airflow distribution in the gravure drying oven.Secondly,this study establishes the multiphase flow model of gravure water-based ink drying for the local area in the drying box to investigate the effects of different factors on the drying efficiency of water-based ink.Taking waterbased ink droplets as an example,a multiphase flow impingement airflow drying model for gravure printing water-based ink is constructed by using the volume of fluid(VOF)method combined with a user-defined function(UDF)compiled based on the mass transfer rate equation for water-based ink drying.Finally,the model is validated in this research.The ink drying state in the impinging airflow region is simulated using the model,and the effects of the temperature and velocity of the impinging airflow as well as the ink viscosity and thickness on the ink drying efficiency are analyzed.The research results show that the reasonable design of the deflector plate can improve the efficiency of hot air drying of gravure printing water-based ink.When the deflector plate is placed between the interval of each air nozzle instead of directly above the air nozzle,the uniformity and speed size of air nozzles 4～7 are improved.In addition,increasing the airflow temperature and airflow speed,reducing the viscosity and thickness of water-based ink,can improve the heat and mass transfer between the airflow and water-based ink,where the airflow velocity is 25m/s,can effectively shorten the drying time of water-based ink.The simulation results in this paper can help designers to predict the effect achieved by the equipment structure of the gravure drying box and avoid the waste caused by back-adjustment in the production process.The multi-phase impact airflow drying model based on the CFD method can provide new research ideas for analyzing the drying characteristics of water-based inks on non-absorbent substrates.This study provides theoretical support for solving the problem of drying difficulties of water-based inks on nonabsorbent flexible packaging substrates to extend the application of water-based inks. |
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