Assemblage of turbulent jet flows through static particulate media/Turbulentsete jugavooluste kogumi liikumine labi osakestega taidetud staatilise keskkonna

• Published in: Proceedings of the Estonian Academy of Sciences p. 284
• Main Authors: Lauk, Peep, Rebassa, Josep Hueso, Kartushinsky, Aleksander, Tisler, Sergei, Tahemaa, Toivo, Polonsky, Andrei
• Format: Journal Article
• Language: English
• Published: Estonian Academy Publishers 01.09.2016
• Subjects: Differential equations, Partial; Jets; Mathematical models; Porous materials; Properties; Turbulence
• ISSN: 1736-6046
• DOI: 10.3176/proc.2016.3.05

The work consists in numerical modelling of two-phase flow in porous media. The performance of a vertical cylinder pellets dryer with four lateral jets discharging air to a motionless particulate medium was modelled. The aim was to better understand the mechanism of heat exchange and the effect of different parameters on the fluid going through a particulate medium. The flow was considered non-isothermal and turbulent. The cases were first calculated for a single phase (isothermal and non-isothermal) and then for two phases with changing the particles volume fraction and size. The Boussinesq approach was used to take into account the effect of temperature on the gas velocity, and the k-∈ model was applied for the closure of momentum equations. The solution algorithm was built using a scheme of finite differences with the tri-diagonal matrix algorithm. The results show how different variables, such as axial velocity or temperature of lateral jets flow, start with high values in the inlets and merge and collapse further downstream while the flow goes through the medium. The axial velocity drops from the jets up to the end of the system. This drop is higher for larger particles volume fractions. The radial velocity tends to increase from a null value faster for larger particles volume fractions. As the drag increases, the temperature drops faster for larger particles volume fractions and for bigger particles, which can be explained by the higher energy transfer between the flow and the particles. Key words: assemblage of jets, multi-phase flow, particulate media, non-isothermal turbulent flow, RANS modelling, TDMA method, pellet dryer. Too koosneb kahefaasilise vooluse numbrilisest modelleerimisest poorse keskkonna tingimustes. Pelletikuivataja tood modelleeritakse voolamisena vertikaalses silindris, millel on neli kulgduusi ohu sisselaskmiseks kuivatatavate osakeste liikumatusse keskkonda. Kaesoleva too eesmark on paremini tunnetada soojusvahetuse mehhanismi ja seda, kuidas erinevad parameetrid mojutavad keskkonda labivat gaasi, et konstrueerida optimaalset kuivatit. Voolust kasitletakse mitteisotermilisena ja arvestatakse niiskusesisalduse muutumisega loplike vahede skeemi. Labiarvutatud juhtumid on esiteks uhe faasi jaoks (isotermiline ja mitteisotermiline) ning siis kahe faasi jaoks, muutes osakeste mahuosa ja nende suurust. Selleks et arvesse votta temperatuuri moju gaasi kiirusele, kasutati Boussinesqi lahendust ja momendivorrandite sulgemiseks rakendati k-e mudelit. Tulemused naitavad erinevate muutujate--eelkoige telgkiiruse ja kulgjugade temperatuuri--moju vaartustele. Sisselaske juures olevad korged vaartused vahenevad voolu keskkonna labimisega. Muutus on suurem osakeste suurema mahu korral, sest see takistab voolu. Radiaalne kiirus kaldub suurenema nullist kiiremini suurema osakeste mahuosa korral, kuna need muudavad voolu suunda. Temperatuur langeb kiiremini suurema osakeste mahuosa korral ja suuremate osakeste puhul, sest takistusjoud suureneb, mida saab tolgendada kui suurenenud energiaulekannet vooluse ning osakeste vahel.