Flow Pattern Analysis on Sticky Regime and Effectiveness of Volume Chamber for Milk Production using CFD Method
Hafid Alwan(a*), Yazid Bindar(b)
a) Department of Chemical Engineering, University of Sultan Ageng Tirtayasa, 42435 Cilegon, Banten, Indonesia
b) Department of Chemical Engineering, Faculty of Industrial Technology, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung, Indonesia
*hafidalwan[at]untirta.ac.id
Abstract
The CFD method is used to evaluate the performance of the spray dryer operation in various geometry and operating conditions. This method is believed to be able to replace, complement, and strengthen the role of the experimental method in resolving problems that occur in the spray drying chamber. Through this method, the design information needed in the cylinder-on-cone spray dryer construction can be obtained. Especially related to the milk drying process. This information is obtained by investigating the performance of the spray dryer with several steps that must be passed. This investigation was conducted aimed at obtaining comprehensive design information. Stages carried out include, constructing thermophysical properties of milk, determining grid generation that includes grid shape and size, determining the size of the geometry of the spray drying chamber, and determining the angle of the droplet spray dryer. Thermophysical properties of milk are constructed in two ways, first using the Aspen Plus® V10 and mathematical equations obtained from experimental data from several researchers. The numerical solution solved through the CFD method using FLUENT ANSYS 19.0. The turbulent model used is Re-Normalized Group-kε (RNG-kε). This turbulent model is believed to be able to provide better results compared to the standard turbulent k-ε model. The standard turbulent k-ε model is built on the basis of turbulent isotropic and turbulent equilibrium, without any correction of the swirl. Through the turbulent model, the swirl RNG-kε found in the spray drying process can be calculated for its contribution. The contribution of the swirl in the turbulent model RNG-kε can be seen through the magnitude of the turbulent viscosity value (μt). The spray drying chamber in this study is represented in two-dimensional geometry (2-D). The shape of the grid used is a triangular (trilateral) form with a total grid of 574.942 elements. Through the shape and number of the grid, the jet pattern is far more stable so that it can minimize the presence of numerical errors. The variables used in this numerical investigation are geometry variable represented by the size of the diameter and spray angle. By using grid size and shape as well as the turbulent RNG-kε model, fluid flow patterns of each variable are obtained. This pattern of fluid flow basically represents the trajectory passed by the particle. Flow patterns that have strong backflow can cause high particle end temperatures. The reason is the particles are held in the drying chamber following the fluid flow. This flow pattern is created in the small size of space and wide spray angle. The problem that is often caused in the presence of particle deposits on the walls and product agglomeration. Through analysis of the droplet evolution curve into particles and sticky area curves, milk droplets can be traced to an area that allows deposits and agglomeration to occur. The result is particle deposition that often occurs in the walls of the cone and the wall near the atomizer. While agglomeration occurs in the product collection area. The design of the spray drying chamber which is considered the best to be built is a spray dryer with 2 m diameter and spray angle of 60 and 100 degrees in order to produce the final product with the low temperature and water content.
Keywords: CFD method, spray dryer, chamber, milk, flow pattern, sticky area
Topic: Chemical Engineering