TY - JOUR
T1 - Numerical analysis of slot die coating of nanocellulosic materials
AU - Panikaveetil Ahamed Kutty, Fuaad
AU - Koppolu, Rajesh
AU - Swerin, Agne
AU - Lundell, Fredrik
AU - Toivakka, Martti
N1 - Eva Höglund: "TAPPI journal ger forskarna tillåtelse att parallellpublicera förlagets version och utan embargo. Det enda de ber är att journalen får publicera artikeln först. Licensfrågan svarade de inte på så bäst att sätta publisher rights policy."
PY - 2020/11
Y1 - 2020/11
N2 - Nanocellulosic coatings as a food packaging material are of commercial interest due to their nontoxic nature, renewability, and excellent barrier properties. Complex shear-thinning rheology poses challenges in designing and sizing equipment to pump, mix, and process the suspension and actual coating process. This study aims to determine the effectiveness of computational fluid dynamics (CFD) in predicting nanocellulosic suspension flow in light of existing rheological data. We employ and compare three distinct rheological models to characterize the rheology and flow of nanocellulose suspensions through a slot die coater, where the model parameters are established from existing slot rheometry measurements. A volume-of-fluid (VoF) based finite volume method is employed to simulate the flow in a slot die operated in an unconventional metering mode. Results with the Casson model predict the presence of unyielded regions in the flow, which was not captured using the power law model. These stagnation regions will incur coatability issues stemming from flow intermittencies and lead to potential defects in the coating layer, including fracture. The results suggest that a rheological model that includes yield stress should be considered while modeling such flows. A need for better rheological data to model nanocellulosic flows, especially at high consistencies and shear rates, is also highlighted.
AB - Nanocellulosic coatings as a food packaging material are of commercial interest due to their nontoxic nature, renewability, and excellent barrier properties. Complex shear-thinning rheology poses challenges in designing and sizing equipment to pump, mix, and process the suspension and actual coating process. This study aims to determine the effectiveness of computational fluid dynamics (CFD) in predicting nanocellulosic suspension flow in light of existing rheological data. We employ and compare three distinct rheological models to characterize the rheology and flow of nanocellulose suspensions through a slot die coater, where the model parameters are established from existing slot rheometry measurements. A volume-of-fluid (VoF) based finite volume method is employed to simulate the flow in a slot die operated in an unconventional metering mode. Results with the Casson model predict the presence of unyielded regions in the flow, which was not captured using the power law model. These stagnation regions will incur coatability issues stemming from flow intermittencies and lead to potential defects in the coating layer, including fracture. The results suggest that a rheological model that includes yield stress should be considered while modeling such flows. A need for better rheological data to model nanocellulosic flows, especially at high consistencies and shear rates, is also highlighted.
UR - https://imisrise.tappi.org/TAPPI/Products/20/NOV/20NOV575.aspx
M3 - Article
VL - 19
SP - 575
EP - 582
JO - Tappi Journal
JF - Tappi Journal
SN - 0734-1415
IS - 11
ER -