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Title:Numerična analiza strižnih napetosti v tekočini med rotacijskim zamrzovanjem viale : magistrsko delo
Authors:ID Špec, Miha (Author)
ID Zadravec, Matej (Mentor) More about this mentor... New window
ID Kamenik, Blaž (Comentor)
Files:.pdf MAG_Spec_Miha_2026.pdf (2,86 MB)
MD5: 2F76A5BD0C3449E25902C4FCFE277823
 
Language:Slovenian
Work type:Master's thesis/paper
Typology:2.09 - Master's Thesis
Organization:FS - Faculty of Mechanical Engineering
Abstract:V magistrskem delu je bila izvedena numerična analiza hidrodinamičnih obremenitev med postopkom rotacijskega zamrzovanja farmacevtskih vial. Obravnavan je bil prehodni večfazni tok tekočine in plina v vialah velikosti 2R, 10R in 50R pri različnih polnitvah ter različnih časih pospeševanja vrtenja do končne hitrosti 4000 obratov na minuto. Namen raziskave je bil določiti vpliv velikosti viale, polnitve in časa pospeševanja na površinsko uteženo povprečno strižno napetost na steni, največjo lokalno strižno napetost na steni ter normalno silo na stransko steno viale. V teoretičnem delu so predstavljene osnove liofilizacije, kontinuirne liofilizacije in rotacijskega zamrzovanja, nato pa še osnovni pojmi numeričnega modeliranja večfaznega toka. RDT model je bil pripravljen v programskem okolju ANSYS Fluent z uporabo metode VOF za opis medfazne površine med tekočo in plinsko fazo. Izvedena je bila verifikacija računske mreže, pripravljena simulacijska matrika ter opravljena obdelava rezultatov za primerjavo največjih in kvazistacionarnih vrednosti izhodnih veličin. Rezultati so pokazali, da največja povprečna strižna napetost ni monotono odvisna od polnitve, saj se najvišje vrednosti pogosto pojavijo pri vmesnih polnitvah, kvazistacionarna normalna sila pa se z večanjem polnitve in velikosti viale praviloma povečuje. Daljši čas pospeševanja izrazito zmanjša prehodne strižne napetosti, medtem ko ima le majhen vpliv na kvazistacionarno normalno silo. Dodatna analiza z metodo Random Forest in nadomestnimi modeli je potrdila, da sta za strižne napetosti najpomembnejša velikost viale in čas pospeševanja, za normalno silo pa predvsem velikost viale in polnitev.
Keywords:RDT, liofilizacija, rotacijsko zamrzovanje, večfazni tok, strižna napetost
Place of publishing:Maribor
Place of performance:Maribor
Publisher:M. Špec
Year of publishing:2026
Number of pages:1 spletni vir (1 datoteka PDF (XI, 69 f.))
PID:20.500.12556/DKUM-99288 New window
UDC:532.5:57.086.13(043.2)
COBISS.SI-ID:291099907 New window
NUK URN:URN:SI:UM:DK:4PICVP66
Publication date in DKUM:27.08.2026
Views:219
Downloads:8
Metadata:XML DC-XML DC-RDF
Categories:KTFMB - FS
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Licences

License:CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Link:http://creativecommons.org/licenses/by-nc-nd/4.0/
Description:The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.
Licensing start date:11.08.2026

Secondary language

Language:English
Title:Numerical analysis of shear stress development in a liquid during vial spin freezing
Abstract:This master’s thesis presents a numerical analysis of hydrodynamic loads during the spin freezing of pharmaceutical vials. A transient multiphase flow of liquid and gas was investigated in 2R, 10R and 50R vials at different fill levels and different acceleration times up to a final rotational speed of 4000 rpm. The aim of the study was to determine the influence of vial size, fill level and acceleration time on the area-weighted average wall shear stress, the maximum local wall shear stress and the quasi-stationary normal force acting on the side wall of the vial. The theoretical part first describes the basics of lyophilization, continuous lyophilization and spin freezing, followed by the main principles of numerical modelling of multiphase flow. The CFD model was prepared in ANSYS Fluent using the VOF method to describe the interface between the liquid and gas phases. A mesh verification study was performed, a simulation matrix was defined and the results were processed in terms of maximum and quasi-stationary output values. The results showed that the maximum average wall shear stress does not vary monotonically with fill level, since the highest values often occur at intermediate fill. In contrast, the quasi-stationary normal force generally increases with increasing fill level and vial size. A longer acceleration time significantly reduces transient shear loads, while it has only a minor influence on the quasi-stationary normal force. An additional Random Forest parameter-importance analysis and surrogate-model comparison confirmed that vial size and acceleration time are the dominant parameters for shear stresses, whereas normal force is mainly governed by vial size and fill level.
Keywords:CFD, lyophilization, spin freezing, multiphase flow, shear stress


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