COBEM99

SR27 Transferência de Calor e Massa

Title:

ANALYSIS OF THE AIR FLOW BETWEEN A MOVING SUBSTRATE AND A CURVED PLATE

Summary :

CONVENTIONAL DRYING OF COATED SUBSTRATES USUALLY USE AIR IMPINGEMENT TO SUPPORT AND HEAT THE COATED WEB. BECAUSE OF THE HIGH VELOCITY AIR FLOW, MOST OF THE HEAT IS TRANSFERRED BY CONVECTION AND THE HEAT TRANSFER COEFFICIENT IS NOT UNIFORM, WHICH CAN LEAD TO DRYING DEFECTS. A WAY OF OVERCOMING THIS PROBLEM AND OBTAIN A HIGH UNIFORM HEAT TRANSFER COEFFICIENT IS TO SUPPLY THE ENERGY TO THE BACK SIDE OF THE SUBSTRATE BY CONDUCTION THROUGH A VERY THIN AIR LAYER BETWEEN A HEATED PLATE AND THE MOVING SUBSTRATE. THEREFORE, IT IS ESSENTIAL TO FORM AND TO BE ABLE TO CONTROL A THIN, UNIFORM AND STABLE AIR LAYER BETWEEN THE SUBSTRATE AND THE HEATING PLATE. THIS WORK PRESENTS A THEORETICAL ANALYSIS OF THE AIR FLOW BETWEEN A MOVING FLEXIBLE SUBSTRATE AND A CURVED SOLID SURFACE. THE GOAL IS TO UNDERSTAND THIS ELASTOHYDRODYNAMIC ACTION AND DETERMINE HOW THE AIR LAYER THICKNESS CHANGES WITH THE PLATE GEOMETRY, SUBSTRATE MATERIAL AND OPERATING CONDITIONS. THE THEORETICAL MODEL CONSISTED OF THE NAVIER-STOKES EQUATION TO DESCRIBE THE AIR MOTION AND CYLINDRICAL SHELL APPROXIMATION TO MODEL THE DEFORMATION OF THE WEB. THE DIFFERENTIAL EQUATIONS WERE SOLVED BY THE GALERKIN / FINITE ELEMENT METHOD. THE AGREEMENT BETWEEN THE PREDICTED AIR LAYER THICKNESS AND THOSE MEASURED EXPERIMENTALLY WAS VERY GOOD. KEY WORDS: ELASTOHYDRODYNAMICS, DRYING, FINITE ELEMENT METHOD.

Author :

Carvalho, Márcio S.
Kolb, Blake B.

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