Thermal transients in a U-bend
•We study the propagation of a hot thermal transient through a U-bend.•The evolution of Dean vortices as the thermal transient passes is studied.•It is found that baroclinic vorticity generation dominates over a large period of the transient, due to the thermal inertia of the wall.•This leads to a r...
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| Veröffentlicht in: | International journal of heat and mass transfer 2020-02, Vol.148, p.119039, Article 119039 |
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| container_title | International journal of heat and mass transfer |
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| creator | Skillen, Alex J. Zimoń, Małgorzata Sawko, Robert Tunstall, Ryan Moulinec, Charles R Emerson, David |
| description | •We study the propagation of a hot thermal transient through a U-bend.•The evolution of Dean vortices as the thermal transient passes is studied.•It is found that baroclinic vorticity generation dominates over a large period of the transient, due to the thermal inertia of the wall.•This leads to a reversal of the Dean vortex secondary flow.
We study numerically the propagation of a hot thermal transient through a U-bend via an ensemble of wall-resolved large eddy simulations. Conjugate heat transfer between fluid and solid domains is accounted for. The flow is in a fully turbulent mixed convection regime, with a bulk Reynolds number of 10,000, a Richardson number of 2.23, and water as the working fluid (Prandtl number = 6). These conditions lead to strong thermal stratification, with buoyancy-induced secondary flows, and the generation of a large and persistent recirculation region.
The evolution of Dean vortices as the thermal transient passes is studied. It is found that baroclinic vorticity generation dominates over a large period of the transient, due to the thermal inertia of the wall. Gravitational buoyancy leads to a reversal of the counter-rotating vortex pair. The impact of this reversal on the swirl-switching and secondary-current losses is assessed. It is found that low frequency modes are suppressed in the reversed-vortex state. |
| doi_str_mv | 10.1016/j.ijheatmasstransfer.2019.119039 |
| format | Article |
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We study numerically the propagation of a hot thermal transient through a U-bend via an ensemble of wall-resolved large eddy simulations. Conjugate heat transfer between fluid and solid domains is accounted for. The flow is in a fully turbulent mixed convection regime, with a bulk Reynolds number of 10,000, a Richardson number of 2.23, and water as the working fluid (Prandtl number = 6). These conditions lead to strong thermal stratification, with buoyancy-induced secondary flows, and the generation of a large and persistent recirculation region.
The evolution of Dean vortices as the thermal transient passes is studied. It is found that baroclinic vorticity generation dominates over a large period of the transient, due to the thermal inertia of the wall. Gravitational buoyancy leads to a reversal of the counter-rotating vortex pair. The impact of this reversal on the swirl-switching and secondary-current losses is assessed. It is found that low frequency modes are suppressed in the reversed-vortex state.</description><identifier>ISSN: 0017-9310</identifier><identifier>EISSN: 1879-2189</identifier><identifier>DOI: 10.1016/j.ijheatmasstransfer.2019.119039</identifier><language>eng</language><publisher>Oxford: Elsevier Ltd</publisher><subject>Baroclinic vorticity generation ; Buoyancy ; Computational fluid dynamics ; Computer simulation ; Convection ; Current loss ; Fluid flow ; Induction heating ; Large eddy simulation ; Nuclear thermal-hydraulics ; Prandtl number ; Reversed secondary flow ; Reynolds number ; Richardson number ; Secondary flow ; Statistically unsteady flow ; Stratified flow ; Thermal stratification ; Thermal transients ; Turbulent flow ; U bends ; Vorticity ; Working fluids</subject><ispartof>International journal of heat and mass transfer, 2020-02, Vol.148, p.119039, Article 119039</ispartof><rights>2019 The Authors</rights><rights>Copyright Elsevier BV Feb 2020</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c428t-20b10f3b81159fc2bf96ff8e42b323b3c468e2e323449424ddce6cbee7a6a4c83</citedby><cites>FETCH-LOGICAL-c428t-20b10f3b81159fc2bf96ff8e42b323b3c468e2e323449424ddce6cbee7a6a4c83</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktohtml>$$Uhttps://dx.doi.org/10.1016/j.ijheatmasstransfer.2019.119039$$EHTML$$P50$$Gelsevier$$Hfree_for_read</linktohtml><link.rule.ids>314,780,784,3550,27924,27925,45995</link.rule.ids></links><search><creatorcontrib>Skillen, Alex</creatorcontrib><creatorcontrib>J. Zimoń, Małgorzata</creatorcontrib><creatorcontrib>Sawko, Robert</creatorcontrib><creatorcontrib>Tunstall, Ryan</creatorcontrib><creatorcontrib>Moulinec, Charles</creatorcontrib><creatorcontrib>R Emerson, David</creatorcontrib><title>Thermal transients in a U-bend</title><title>International journal of heat and mass transfer</title><description>•We study the propagation of a hot thermal transient through a U-bend.•The evolution of Dean vortices as the thermal transient passes is studied.•It is found that baroclinic vorticity generation dominates over a large period of the transient, due to the thermal inertia of the wall.•This leads to a reversal of the Dean vortex secondary flow.
We study numerically the propagation of a hot thermal transient through a U-bend via an ensemble of wall-resolved large eddy simulations. Conjugate heat transfer between fluid and solid domains is accounted for. The flow is in a fully turbulent mixed convection regime, with a bulk Reynolds number of 10,000, a Richardson number of 2.23, and water as the working fluid (Prandtl number = 6). These conditions lead to strong thermal stratification, with buoyancy-induced secondary flows, and the generation of a large and persistent recirculation region.
The evolution of Dean vortices as the thermal transient passes is studied. It is found that baroclinic vorticity generation dominates over a large period of the transient, due to the thermal inertia of the wall. Gravitational buoyancy leads to a reversal of the counter-rotating vortex pair. The impact of this reversal on the swirl-switching and secondary-current losses is assessed. It is found that low frequency modes are suppressed in the reversed-vortex state.</description><subject>Baroclinic vorticity generation</subject><subject>Buoyancy</subject><subject>Computational fluid dynamics</subject><subject>Computer simulation</subject><subject>Convection</subject><subject>Current loss</subject><subject>Fluid flow</subject><subject>Induction heating</subject><subject>Large eddy simulation</subject><subject>Nuclear thermal-hydraulics</subject><subject>Prandtl number</subject><subject>Reversed secondary flow</subject><subject>Reynolds number</subject><subject>Richardson number</subject><subject>Secondary flow</subject><subject>Statistically unsteady flow</subject><subject>Stratified flow</subject><subject>Thermal stratification</subject><subject>Thermal transients</subject><subject>Turbulent flow</subject><subject>U bends</subject><subject>Vorticity</subject><subject>Working fluids</subject><issn>0017-9310</issn><issn>1879-2189</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2020</creationdate><recordtype>article</recordtype><recordid>eNqNkE1LAzEQhoMoWKt_QRa8eNk1k6RpclOKnxS8tOeQZCc0S7tbk63gv3frevPiaWaY4Rneh5BboBVQkHdNFZsN2n5nc-6TbXPAVDEKugLQlOsTMgE11yUDpU_JhFKYl5oDPScXOTfHkQo5IderDaad3RY_jIhtn4vYFrZYlw7b-pKcBbvNePVbp2T99LhavJTL9-fXxcOy9IKpvmTUAQ3cKYCZDp65oGUICgVznHHHvZAKGQ69EFowUdcepXeIcyut8IpPyc3I3afu44C5N013SO3w0jA-Y1wqruhwdT9e-dTlnDCYfYo7m74MUHO0Yhrz14o5WjGjlQHxNiJwSPMZh232Q2qPdUzoe1N38f-wbz0edeE</recordid><startdate>202002</startdate><enddate>202002</enddate><creator>Skillen, Alex</creator><creator>J. Zimoń, Małgorzata</creator><creator>Sawko, Robert</creator><creator>Tunstall, Ryan</creator><creator>Moulinec, Charles</creator><creator>R Emerson, David</creator><general>Elsevier Ltd</general><general>Elsevier BV</general><scope>6I.</scope><scope>AAFTH</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7TB</scope><scope>8FD</scope><scope>FR3</scope><scope>H8D</scope><scope>KR7</scope><scope>L7M</scope></search><sort><creationdate>202002</creationdate><title>Thermal transients in a U-bend</title><author>Skillen, Alex ; J. 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Zimoń, Małgorzata</creatorcontrib><creatorcontrib>Sawko, Robert</creatorcontrib><creatorcontrib>Tunstall, Ryan</creatorcontrib><creatorcontrib>Moulinec, Charles</creatorcontrib><creatorcontrib>R Emerson, David</creatorcontrib><collection>ScienceDirect Open Access Titles</collection><collection>Elsevier:ScienceDirect:Open Access</collection><collection>CrossRef</collection><collection>Mechanical & Transportation Engineering Abstracts</collection><collection>Technology Research Database</collection><collection>Engineering Research Database</collection><collection>Aerospace Database</collection><collection>Civil Engineering Abstracts</collection><collection>Advanced Technologies Database with Aerospace</collection><jtitle>International journal of heat and mass transfer</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Skillen, Alex</au><au>J. Zimoń, Małgorzata</au><au>Sawko, Robert</au><au>Tunstall, Ryan</au><au>Moulinec, Charles</au><au>R Emerson, David</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Thermal transients in a U-bend</atitle><jtitle>International journal of heat and mass transfer</jtitle><date>2020-02</date><risdate>2020</risdate><volume>148</volume><spage>119039</spage><pages>119039-</pages><artnum>119039</artnum><issn>0017-9310</issn><eissn>1879-2189</eissn><abstract>•We study the propagation of a hot thermal transient through a U-bend.•The evolution of Dean vortices as the thermal transient passes is studied.•It is found that baroclinic vorticity generation dominates over a large period of the transient, due to the thermal inertia of the wall.•This leads to a reversal of the Dean vortex secondary flow.
We study numerically the propagation of a hot thermal transient through a U-bend via an ensemble of wall-resolved large eddy simulations. Conjugate heat transfer between fluid and solid domains is accounted for. The flow is in a fully turbulent mixed convection regime, with a bulk Reynolds number of 10,000, a Richardson number of 2.23, and water as the working fluid (Prandtl number = 6). These conditions lead to strong thermal stratification, with buoyancy-induced secondary flows, and the generation of a large and persistent recirculation region.
The evolution of Dean vortices as the thermal transient passes is studied. It is found that baroclinic vorticity generation dominates over a large period of the transient, due to the thermal inertia of the wall. Gravitational buoyancy leads to a reversal of the counter-rotating vortex pair. The impact of this reversal on the swirl-switching and secondary-current losses is assessed. It is found that low frequency modes are suppressed in the reversed-vortex state.</abstract><cop>Oxford</cop><pub>Elsevier Ltd</pub><doi>10.1016/j.ijheatmasstransfer.2019.119039</doi><oa>free_for_read</oa></addata></record> |
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| subjects | Baroclinic vorticity generation Buoyancy Computational fluid dynamics Computer simulation Convection Current loss Fluid flow Induction heating Large eddy simulation Nuclear thermal-hydraulics Prandtl number Reversed secondary flow Reynolds number Richardson number Secondary flow Statistically unsteady flow Stratified flow Thermal stratification Thermal transients Turbulent flow U bends Vorticity Working fluids |
| title | Thermal transients in a U-bend |
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