Study of advanced rheology models
(2019) MVKM01 20191Department of Energy Sciences
- Abstract
- For Tetra Pak to be able to continue its work on minimizing energy usage and waste in its production systems and delivering better solutions for its customers, it is of the utmost importance to understand the products used in the Tetra Pak system. Many of these products are defined as semi-fluid products, which means they can behave like both fluids and solids, depending on the circumstances. Understanding which rheological properties that can be modeled with different types of mathematical models and what type of experimental data that is needed for these models is therefore of the utmost importance and is the main focus of this thesis.
Two mathematical models for a shear rate-dependent viscosity were studied. A power law model and a... (More) - For Tetra Pak to be able to continue its work on minimizing energy usage and waste in its production systems and delivering better solutions for its customers, it is of the utmost importance to understand the products used in the Tetra Pak system. Many of these products are defined as semi-fluid products, which means they can behave like both fluids and solids, depending on the circumstances. Understanding which rheological properties that can be modeled with different types of mathematical models and what type of experimental data that is needed for these models is therefore of the utmost importance and is the main focus of this thesis.
Two mathematical models for a shear rate-dependent viscosity were studied. A power law model and a Herschel Bulkley model whose purpose is to model a solid behaviour at low shear rates with an extremely high viscosity. Four models where the combination of a differential equation and a viscosity model were combined to make the viscosity both dependent on the shear rate and the degradation of the microstructure of the product over time, so-called thixotropy, were also studied. A viscoelastic model whose purpose is to fully combine both a solid and a fluid behaviour was studied briefly.
Data fitting strategies were used to adapt the models to experimental data and the models usefulness was evaluated with how well the experimental data could be reproduced. A number of the models were implemented and further studied with more advanced simulations in ANSYS Fluent to be able to make a more detailed study of their suitability by comparing with experimental data. The CFD simulations included steady state simulations for a Bob & Cup rheometer and extensional rheometer, as well as a transient simulation to study how the surface profile behaves as it moves down a plate.
The conclusion was that the Herschel Bulkley model seemed most suitable for modelling the behaviour at low shear rates and appeared to generally represent the two products Vaniljyoghurt and Yoghurt Naturell best. Non of the models considered could fully capture the behaviour observed for Långfil. Of the four thixotropy models studied, a better fit with experimental data was obtained for a model that could not be implemented in Fluent because of its nonlinear nature. Hence, one of the less promising models was implemented to see if the addition of a time-dependent model made any major difference to the product behaviour for the transient simulation, which did not seem to be the case. However, it was found that the use of a surface tension model played a major role in the surface behaviour for a fluid flowing down a plate. It also turned out that the viscoelastic model could not be adapted to the experimental data available at all. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/8983588
- author
- Jönsson, Gustaf LU
- supervisor
- organization
- course
- MVKM01 20191
- year
- 2019
- type
- H2 - Master's Degree (Two Years)
- subject
- report number
- LUTMDN/TMHP-19/5440-SE
- ISSN
- 0282-1990
- language
- English
- id
- 8983588
- date added to LUP
- 2019-07-02 10:57:44
- date last changed
- 2019-07-02 10:57:44
@misc{8983588,
abstract = {{For Tetra Pak to be able to continue its work on minimizing energy usage and waste in its production systems and delivering better solutions for its customers, it is of the utmost importance to understand the products used in the Tetra Pak system. Many of these products are defined as semi-fluid products, which means they can behave like both fluids and solids, depending on the circumstances. Understanding which rheological properties that can be modeled with different types of mathematical models and what type of experimental data that is needed for these models is therefore of the utmost importance and is the main focus of this thesis.
Two mathematical models for a shear rate-dependent viscosity were studied. A power law model and a Herschel Bulkley model whose purpose is to model a solid behaviour at low shear rates with an extremely high viscosity. Four models where the combination of a differential equation and a viscosity model were combined to make the viscosity both dependent on the shear rate and the degradation of the microstructure of the product over time, so-called thixotropy, were also studied. A viscoelastic model whose purpose is to fully combine both a solid and a fluid behaviour was studied briefly.
Data fitting strategies were used to adapt the models to experimental data and the models usefulness was evaluated with how well the experimental data could be reproduced. A number of the models were implemented and further studied with more advanced simulations in ANSYS Fluent to be able to make a more detailed study of their suitability by comparing with experimental data. The CFD simulations included steady state simulations for a Bob & Cup rheometer and extensional rheometer, as well as a transient simulation to study how the surface profile behaves as it moves down a plate.
The conclusion was that the Herschel Bulkley model seemed most suitable for modelling the behaviour at low shear rates and appeared to generally represent the two products Vaniljyoghurt and Yoghurt Naturell best. Non of the models considered could fully capture the behaviour observed for Långfil. Of the four thixotropy models studied, a better fit with experimental data was obtained for a model that could not be implemented in Fluent because of its nonlinear nature. Hence, one of the less promising models was implemented to see if the addition of a time-dependent model made any major difference to the product behaviour for the transient simulation, which did not seem to be the case. However, it was found that the use of a surface tension model played a major role in the surface behaviour for a fluid flowing down a plate. It also turned out that the viscoelastic model could not be adapted to the experimental data available at all.}},
author = {{Jönsson, Gustaf}},
issn = {{0282-1990}},
language = {{eng}},
note = {{Student Paper}},
title = {{Study of advanced rheology models}},
year = {{2019}},
}