Numerical and experimental studies of thin liquid film flow between two forward-rollers

Roll coating is a widely used industrial technique to deposit a thin and uniform liquid film on a sheet or solid substrate. In this paper the three dimensional forward roll coating process has been studied by both experiments and numerical simulations. Experiments were conducted on a 2 roll coating system of pick up roll and application roll using two samples of 50% and 70% by weight aqueous glycerin solutions. The gap between the two rollers at nip was maintained at 100 microns. The coating film thickness and the distance of the film splitting point from the nip were measured during the experiments. The coating film thickness was determined for different speed ratios for both samples. 3D Numerical simulations for forward coating process have been carried out and the simulation results were verified were with experiments. They match very well, the error between them being 5% to 10%.