There is a growing interest in using unbaffled stirred tanks for addressing a number of processing needs such as low shear damage (sensitive biocultures), low attrition (solid–liquid applications), deep-cleaning/ sterilization (pharmaceutical applications). The main feature of uncovered, unbaffled stirred tanks is highly swirling motion of the fluid that results in a deformation of the free liquid surface. At sufficiently high agitation speeds the resulting whirlpool reaches the impeller and gives rise to a gas–liquid dispersion, so leading to the formation of a dispersion without the use of gas-sparger; the so-called self-inducing operation of the vessel. In this work, digital image analysis coupled with a suitable shadowgraphy-based technique is used to investigate the shape of the free-surface that forms in uncovered unbaffled stirred tanks, when different stirrer geometries are considered. The technique is based on back-lighting the vessel and suitably averaging over time the recorded free surface shape. For each investigated geometry, the deformed free-surface was analyzed at different impeller speeds. Different geometries of the vessel were analyzed, by varying impeller distance from vessel bottom as well as agitator type (Rushton turbine, Lightnin A310, Pitched Blade Turbine). It is shown that impeller design strongly affects the free surface profile, and in turn the impeller speed at which the free surface reaches the impeller. A model was developed to fully describe free-surface profile at all agitation speeds and for all investigated geometries, suitable for being adapted to experiments by means of physically consistent parameters adjustment.

Busciglio, A., Caputo, G., Scargiali, F. (2013). Free-surface shape in unbaffled stirred vessels: Experimental study via digital image analysis. CHEMICAL ENGINEERING SCIENCE, 104, 868-880 [http://dx.doi.org/10.1016/j.ces.2013.10.019].

Free-surface shape in unbaffled stirred vessels: Experimental study via digital image analysis

CAPUTO, Giuseppe;SCARGIALI, Francesca
2013-01-01

Abstract

There is a growing interest in using unbaffled stirred tanks for addressing a number of processing needs such as low shear damage (sensitive biocultures), low attrition (solid–liquid applications), deep-cleaning/ sterilization (pharmaceutical applications). The main feature of uncovered, unbaffled stirred tanks is highly swirling motion of the fluid that results in a deformation of the free liquid surface. At sufficiently high agitation speeds the resulting whirlpool reaches the impeller and gives rise to a gas–liquid dispersion, so leading to the formation of a dispersion without the use of gas-sparger; the so-called self-inducing operation of the vessel. In this work, digital image analysis coupled with a suitable shadowgraphy-based technique is used to investigate the shape of the free-surface that forms in uncovered unbaffled stirred tanks, when different stirrer geometries are considered. The technique is based on back-lighting the vessel and suitably averaging over time the recorded free surface shape. For each investigated geometry, the deformed free-surface was analyzed at different impeller speeds. Different geometries of the vessel were analyzed, by varying impeller distance from vessel bottom as well as agitator type (Rushton turbine, Lightnin A310, Pitched Blade Turbine). It is shown that impeller design strongly affects the free surface profile, and in turn the impeller speed at which the free surface reaches the impeller. A model was developed to fully describe free-surface profile at all agitation speeds and for all investigated geometries, suitable for being adapted to experiments by means of physically consistent parameters adjustment.
2013
Settore ING-IND/25 - Impianti Chimici
Busciglio, A., Caputo, G., Scargiali, F. (2013). Free-surface shape in unbaffled stirred vessels: Experimental study via digital image analysis. CHEMICAL ENGINEERING SCIENCE, 104, 868-880 [http://dx.doi.org/10.1016/j.ces.2013.10.019].
File in questo prodotto:
File Dimensione Formato  
Busciglio_CES2013b_COMP.pdf

Solo gestori archvio

Dimensione 4.06 MB
Formato Adobe PDF
4.06 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10447/89784
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 59
  • ???jsp.display-item.citation.isi??? 50
social impact