Unsteady multi-phase mass transfer modeling and analysis for the process of the ammonia volatilization from yarn bobbin

An unsteady multi-phase mass transfer model is developed to analyze and discuss the mass transfer characteristics in the process of the ammonia volatilization from yarn bobbin. The model considers the mass diffusion in the porous material, concentration distribution in boundary layer and the mass convection diffusion in the air flow. The five key parameters of the model are solved by giving the analytic expressions and calculating formulas expectively. With the experimental results from lattice distortion modification production equipment, the two main unknown parameters of the concentration partition coefficient and the diffusion coefficient were determined by data fitting method based on the proposed mass transfer model. The mass transfer model was used to investigate the ammonia medium mass transfer characteristics. The results show that the concentration distribution in the yarn bobbin is mainly related to the air flow velocity and the volatilization time. The concentration gradient between the center and the surface enhances with the increasing of the air flow velocity. But the impact of the air flow velocity on the concentration gradient decreases with the volatilization time extension. The mass transfer rate improves with the air flow velocity increasing, and decreases with the yarn bobbin radius increasing. The normalized concentration and the normalized volatilized mass have no relation with the initial concentration, but are just determined by the inherent mass transfer properties of the ammonia medium in yarn bobbin.