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ORAL PRESENTATION
Session: 4 Complex fluid deformation and rheology: Theories and thermodynamic relationships
(scheduled: Tuesday, 11:10 )
Thermodynamics of Non-Isothermal Polymer Flows: Experiment, Theory and Simulation
T.C. Ionescu1, B.J. Edwards1, D.J. Keffer1, V.G. Mavrantzas2
1 Department of Chemical Engineering, University of Tennessee, Knoxville, TN 37996-2200, USA
2 Department of Chemical Engineering, University of Patras, Patras GR 26504, Greece
We provide a critical evaluation of the so-called ''Theory of Purely Entropic Elasticity'', which states that the free energy change of a flowing, non-isothermal viscoelastic fluid is entirely due to entropic effects, and contains no contributions due to elastic energy changes. Our investigation consists of both theoretical and experimental parts. In the theoretical part, we perform non-equilibrium Monte Carlo simulations to calculate both the energetic and entropic contributions to the free energy of the material under uniaxial elongational flow. This results in measurable energetic effects at higher strain rates, and these effects increase as temperature decreases. Experimentally, we measured the heat capacity at constant volume of LDPE under steady-state shear and uniaxial elongational flow conditions, and calculated the conformational contribution to this quantity. According to the Theory of Purely Entropic Elasticity, the conformational contribution to the heat capacity should be negligible, however, significant non-vanishing contributions are measurable at high strain rates. Results are qualitatively consistent between theory and simulation. © IWNET 2006
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and Kleanthi for IWNET 2006