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CFD-based analysis of oil circulation in ONAN-cooled power transformer radiators.

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Title: CFD-based analysis of oil circulation in ONAN-cooled power transformer radiators.
Authors: Garelli, Luciano1 (AUTHOR) lgarelli@cimec.unl.edu.ar, Ríos Rodriguez, Gustavo Adolfo1 (AUTHOR) gusadrr@santafe-conicet.gov.ar, Storti, Mario Alberto1 (AUTHOR) mario.storti@cimec.unl.edu.ar
Source: International Journal of Numerical Methods for Heat & Fluid Flow. 2026, Vol. 36 Issue 7, p2718-2744. 27p.
Subjects: Radiators, Computational fluid dynamics, Insulating oils, Energy dissipation, Natural heat convection, Heat transfer fluids, Power transformers
Abstract: Purpose: This study aims to use computational fluid dynamics (CFD) simulations to investigate the thermofluid dynamics and oil circulation in power transformer radiators working in oil natural air natural mode. Design/methodology/approach: Two numerical approaches are compared: a closed-loop buoyancy-driven flow model capturing the oil natural convection and a simplified model that imposes the oil mass flow rate at the upper collector of the radiator bank. First, a set of numerical simulations is conducted assuming a fixed power loss per fin for radiator configurations featuring 1, 5 and 15 fins, and the results are validated against a reduced semianalytical model. Findings: The analysis reveals that the imposed mass flow rate boundary condition yields a higher average outlet temperature and approximately 5% lower dissipated power compared with the natural convection model. Furthermore, experimental data on radiator fin temperature and oil mass flow rate were compared with numerical simulations using both approaches. Although this discrepancy is acceptable from an engineering perspective, oil flow distribution within the fin channels is significantly modified by the type of boundary condition being used. The analysis leads to notable differences in the oil local velocity and temperature fields, affecting the fin surface temperature distribution. Originality/value: The findings indicate that although the forced-circulation approach is useful to estimate the overall dissipated power, it is inadequate for detailed internal thermofluid dynamic analyses. The implications of this work are critical for the accurate design and performance evaluation of power transformer radiators. [ABSTRACT FROM AUTHOR]
Copyright of International Journal of Numerical Methods for Heat & Fluid Flow is the property of Emerald Publishing Limited and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
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Header DbId: egs
DbLabel: Engineering Source
An: 194733977
AccessLevel: 6
PubType: Academic Journal
PubTypeId: academicJournal
PreciseRelevancyScore: 0
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Items – Name: Title
  Label: Title
  Group: Ti
  Data: CFD-based analysis of oil circulation in ONAN-cooled power transformer radiators.
– Name: Author
  Label: Authors
  Group: Au
  Data: <searchLink fieldCode="AR" term="%22Garelli%2C+Luciano%22">Garelli, Luciano</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> lgarelli@cimec.unl.edu.ar</i><br /><searchLink fieldCode="AR" term="%22Ríos+Rodriguez%2C+Gustavo+Adolfo%22">Ríos Rodriguez, Gustavo Adolfo</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> gusadrr@santafe-conicet.gov.ar</i><br /><searchLink fieldCode="AR" term="%22Storti%2C+Mario+Alberto%22">Storti, Mario Alberto</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> mario.storti@cimec.unl.edu.ar</i>
– Name: TitleSource
  Label: Source
  Group: Src
  Data: <searchLink fieldCode="JN" term="%22International+Journal+of+Numerical+Methods+for+Heat+%26+Fluid+Flow%22">International Journal of Numerical Methods for Heat & Fluid Flow</searchLink>. 2026, Vol. 36 Issue 7, p2718-2744. 27p.
– Name: Subject
  Label: Subjects
  Group: Su
  Data: <searchLink fieldCode="DE" term="%22Radiators%22">Radiators</searchLink><br /><searchLink fieldCode="DE" term="%22Computational+fluid+dynamics%22">Computational fluid dynamics</searchLink><br /><searchLink fieldCode="DE" term="%22Insulating+oils%22">Insulating oils</searchLink><br /><searchLink fieldCode="DE" term="%22Energy+dissipation%22">Energy dissipation</searchLink><br /><searchLink fieldCode="DE" term="%22Natural+heat+convection%22">Natural heat convection</searchLink><br /><searchLink fieldCode="DE" term="%22Heat+transfer+fluids%22">Heat transfer fluids</searchLink><br /><searchLink fieldCode="DE" term="%22Power+transformers%22">Power transformers</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Purpose: This study aims to use computational fluid dynamics (CFD) simulations to investigate the thermofluid dynamics and oil circulation in power transformer radiators working in oil natural air natural mode. Design/methodology/approach: Two numerical approaches are compared: a closed-loop buoyancy-driven flow model capturing the oil natural convection and a simplified model that imposes the oil mass flow rate at the upper collector of the radiator bank. First, a set of numerical simulations is conducted assuming a fixed power loss per fin for radiator configurations featuring 1, 5 and 15 fins, and the results are validated against a reduced semianalytical model. Findings: The analysis reveals that the imposed mass flow rate boundary condition yields a higher average outlet temperature and approximately 5% lower dissipated power compared with the natural convection model. Furthermore, experimental data on radiator fin temperature and oil mass flow rate were compared with numerical simulations using both approaches. Although this discrepancy is acceptable from an engineering perspective, oil flow distribution within the fin channels is significantly modified by the type of boundary condition being used. The analysis leads to notable differences in the oil local velocity and temperature fields, affecting the fin surface temperature distribution. Originality/value: The findings indicate that although the forced-circulation approach is useful to estimate the overall dissipated power, it is inadequate for detailed internal thermofluid dynamic analyses. The implications of this work are critical for the accurate design and performance evaluation of power transformer radiators. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of International Journal of Numerical Methods for Heat & Fluid Flow is the property of Emerald Publishing Limited and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 27
        StartPage: 2718
    Subjects:
      – SubjectFull: Radiators
        Type: general
      – SubjectFull: Computational fluid dynamics
        Type: general
      – SubjectFull: Insulating oils
        Type: general
      – SubjectFull: Energy dissipation
        Type: general
      – SubjectFull: Natural heat convection
        Type: general
      – SubjectFull: Heat transfer fluids
        Type: general
      – SubjectFull: Power transformers
        Type: general
    Titles:
      – TitleFull: CFD-based analysis of oil circulation in ONAN-cooled power transformer radiators.
        Type: main
  BibRelationships:
    HasContributorRelationships:
      – PersonEntity:
          Name:
            NameFull: Garelli, Luciano
      – PersonEntity:
          Name:
            NameFull: Ríos Rodriguez, Gustavo Adolfo
      – PersonEntity:
          Name:
            NameFull: Storti, Mario Alberto
    IsPartOfRelationships:
      – BibEntity:
          Dates:
            – D: 01
              M: 07
              Text: 2026
              Type: published
              Y: 2026
          Identifiers:
            – Type: issn-print
              Value: 09615539
          Numbering:
            – Type: volume
              Value: 36
            – Type: issue
              Value: 7
          Titles:
            – TitleFull: International Journal of Numerical Methods for Heat & Fluid Flow
              Type: main
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