Thermal and mechanical stresses in bayonet tubes of solar central receivers working with molten salt and liquid sodium

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dc.contributor.author Pérez Álvarez, Rafael
dc.contributor.author Acosta Iborra, Antonio
dc.contributor.author Santana Santana, Domingo José
dc.date.accessioned 2021-04-23T11:00:58Z
dc.date.available 2021-04-23T11:00:58Z
dc.date.issued 2020-03
dc.identifier.bibliographicCitation Pérez-Álvarez, R., Acosta-Iborra, A. & Santana, D. (2020). Thermal and mechanical stresses in bayonet tubes of solar central receivers working with molten salt and liquid sodium. Results in Engineering, 5, 100073.
dc.identifier.issn 2590-1230
dc.identifier.uri http://hdl.handle.net/10016/32473
dc.description.abstract One of the most promising technologies for solar thermal power are solar power towers (SPTs), in which direct solar radiation is redirected by heliostats to a receiver located on top of a tower. The technology used by SPT allows obtaining high thermal efficiencies as well as a high number of hours of operation thanks to thermal storage. However, the high thermal gradients to which the receiver is subjected, in addition to the corrosion of the molten solar salt, can cause the rupture of the receiver and this limits the maximum irradiation the receiver can withstand. To overcome this problem there are different strategies, such as the use of working fluids that are less corrosive than molten salts or the development of new designs of the receiver to avoid overheating of the pipes. In this work we analyze the thermal and structural behavior of a new design of SPT receiver in which bayonet tubes are used instead of simple tubes. A bayonet tube consists of a tube inside another one. In the bayonet tube the working fluid first circulates through the inner tube and then through the annular section between the tubes. An eccentric bayonet tube, created by displacing the inner tube with regards the outer tube, reduces the overheating of the fluid and the outer tube wall as will be shown later. Besides, this work also assesses the effect of using either molten salt or liquid sodium as a working fluid on the thermal and structural behavior of the absorber tube. Since the extreme thermal conditions of central receivers preclude a detailed experimental analysis, the analyses of the present work are performed through multi-physics (CFD – FEM) simulations of the working fluid flow in the annular section and the stresses in the outer wall of the bayonet tube, which are the most critical elements of the receiver. In particular, to perform the hydrodynamic and thermal analysis of the fluid section and the outer wall of the tube, the RANS equations of the fluid together with the turbulent RSM model and the head diffusion equation of the wall were solved using ANSYS Fluent v18 CFD code. Boundary conditions of temperature and non-uniform irradiation were selected to represent typical operative conditions of receivers. Subsequently, using the temperature profiles obtained from the CFD simulations for each working fluid, ANSYS Workbench v18 was employed to obtain the thermal and mechanical stresses in the outer tube as a function of its different constraints, including the attachment of the tube. The results obtained with the CFD – FEM simulations show that, regardless of the working fluid, the eccentricity of the bayonet tube decreases local peaks of temperature in the flow and temperature gradients in the outer tube wall, which leads to a reduction of the wall stresses of the SPT receiver. Furthermore, thanks to its high conductivity, liquid sodium is able to yield lower temperature gradients and stresses in the wall, independently of the kind of tube, compared to molten salt.
dc.format.extent 9
dc.language.iso eng
dc.publisher Elsevier
dc.rights © 2019 The Author(s).
dc.rights Atribución-NoComercial-SinDerivadas 3.0 España
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/es/
dc.subject.other Bayonet tube
dc.subject.other Liquid sodium
dc.subject.other Molten salt
dc.subject.other Non-uniform heat flux
dc.subject.other Solar power tower
dc.subject.other Solar receiver
dc.subject.other Thermal stresses
dc.title Thermal and mechanical stresses in bayonet tubes of solar central receivers working with molten salt and liquid sodium
dc.type article
dc.subject.eciencia Energías Renovables
dc.identifier.doi https://doi.org/10.1016/j.rineng.2019.100073
dc.rights.accessRights openAccess
dc.relation.projectID Gobierno de España. RTI2018-096664-B-C21
dc.relation.projectID Gobierno de España. ENE2015-69486-R
dc.type.version publishedVersion
dc.identifier.publicationfirstpage 100073-1
dc.identifier.publicationlastpage 100073-9
dc.identifier.publicationtitle Results in Engineering
dc.identifier.publicationvolume 5
dc.identifier.uxxi AR/0000025628
dc.contributor.funder Ministerio de Economía y Competitividad (España)
dc.contributor.funder Ministerio de Ciencia, Innovación y Universidades (España)
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