Computational Fluid Dynamics Analysis of Recycled Paper Packaging Drying Processes: Master thesis
Author
Kristensen, Jakob Rosenkilde
Term
4. semester
Education
Publication year
2024
Submitted on
2024-06-01
Pages
100
Abstract
This thesis investigates how computational fluid dynamics (CFD) can reliably model the drying of recycled paper packaging by representing coupled heat and mass transfer in both the surrounding airflow and the paper matrix. The work separates the problem into a steady-state model that captures the nearly constant mid-drying evaporation rate and a transient model that resolves time-dependent changes in temperature and moisture content. CFD simulations in Ansys Fluent (two- and three-dimensional) are used to compute heat and mass transfer and evaporation rates, while a Python implementation evaluates in-paper transport processes for the transient case. A controlled drying-oven setup provides temperature, humidity, and airflow data used as boundary conditions and for comparison. Across turbulence models and meshes, the k-ω SST model gave the most accurate evaporation-rate predictions, closely matching measurements, although achieving an experimental energy balance remains challenging. The study indicates that a two-way coupling between Ansys Fluent and the Python model could improve fidelity. Overall, the results show that CFD combined with numerical drying models can predict the drying behavior of complex recycled-paper geometries, exemplified by egg packaging.
Specialet undersøger, hvordan Computational Fluid Dynamics (CFD) kan modellere tørring af genanvendt papiremballage ved at beskrive koblet varme- og stoftransport i både luftstrømmen og papirmatricen. Problemstillingen opdeles i en stationær model, der beskriver den næsten konstante fordampningsrate i tørringens mellemfase, og en transient model, der fanger de tidsafhængige ændringer i temperatur og fugtindhold. CFD-beregninger i Ansys Fluent (2D og 3D) anvendes til at bestemme varme- og stofoverførsel samt fordampningsrater, mens en Python-implementering evaluerer transportfænomener i papiret for den transiente model. En kontrolleret tørreovn leverer temperatur-, fugtigheds- og strømningsdata til randbetingelser og sammenligning. På tværs af turbulensmodeller og net viste k-ω SST-modellen de mest præcise forudsigelser af fordampningsrater og stemte tæt overens med målinger, men det er fortsat udfordrende at opnå energibalance i niveau med forsøgene. Studiet peger på, at en tovejskobling mellem Ansys Fluent og Python-modellen kan øge nøjagtigheden. Samlet viser resultaterne, at CFD kombineret med numeriske tørringsmodeller kan forudsige tørringsadfærden for komplekse papirgeometrier, eksemplificeret ved æggebakker.
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