Numerical modelling of paint curing in convective ovens

M. Vasudevan. Master thesis, Chalmers University of Technology, Supervisor Srdjan Sasic. 12 June 2018.

Abstract

The paint application and the curing process is a crucial step in the automotive production lines as it accounts for both aesthetic appeal and protection against corrosion. The requirement of a standard for the paint curing process and quantification for improving performance parameters is the primary motivation for developing a mathematical model based on first principles. The complex curing process involves conjugate heat transfer, mass transfer and polymerization process.

Extensive Three-Dimensional Computational Fluid Dynamics (CFD) based studies have been made in the literature with One-Dimensional mass transport modeling of the solvent at the paint layer-air interface with no resolution of heat transport within the same. Representative experiments of the curing process have been performed by Swerea-IVF and the measurements signify the importance of resolution of heat transport within the paint layer. The current study is intended to provide Heat Transfer Co-efficient (HTC) for the Three-Dimensional CFD simulations. The temporal resolution of the heat transport equation within the paint layer creates large separations of time scales and this makes the computational requirements in-feasible for the current scale of problem. A known value of HTC in the Three-dimensional CFD simulations provides an opportunity to avoid solving heat transfer in different phases simultaneously. Therefore, the current work is an attempt towards benefiting from both experiments and numerical techniques as One-Dimensional simulations have been developed to characterize the heat and mass transport within the paint layer to result in the optimized HTC based on the experimental measurements.

The work involved optimization of HTC in the heat transfer solver and a model parameter that represents evaporation at the paint layer-air interface in the mass transfer solver. It is observed in the work that the HTC is a strong function of concentration of solvent and the model parameter in the mass transport equation increased with decreasing concentration of the solvent. The model parameter in the mass transport equation is invariant with the temperature.




Photo credits: Nic McPhee