Understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization

Abstract Nanofluids (NFs) are colloidal suspensions of nanoparticles (NPs) within a base fluid. Unlike conventional mixtures, NFs exhibit dramatically enhanced properties, such as an abnormal increase in heat capacity at low concentration of NPs (e.g., Cp values 30% higher than the base material val...

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Autores principales:	Adela Svobodova-Sedlackova, Alejandro Calderón, Camila Barreneche, Pablo Gamallo, A. Inés Fernández
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/8836eed336394689b84721119ee1629e
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spelling	oai:doaj.org-article:8836eed336394689b84721119ee1629e2021-12-02T13:33:51ZUnderstanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization10.1038/s41598-021-84292-92045-2322https://doaj.org/article/8836eed336394689b84721119ee1629e2021-03-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-84292-9https://doaj.org/toc/2045-2322Abstract Nanofluids (NFs) are colloidal suspensions of nanoparticles (NPs) within a base fluid. Unlike conventional mixtures, NFs exhibit dramatically enhanced properties, such as an abnormal increase in heat capacity at low concentration of NPs (e.g., Cp values 30% higher than the base material value). Understanding the thermo-physical behavior of NFs is essential for their application as thermal energy storage systems. In this study, we analyze a sodium nitrate ionic system containing 1 wt%, 3 wt% and 7 wt% of SiO2 NPs with different techniques like infrared thermography, infrared spectroscopy and differential scanning calorimetry (DSC) in order to shed light on the mechanism behind the increase of Cp. The themographies reveal the presence of a colder layer on top of the NF with 1 wt% of NPs whereas this layer does not appear at higher concentrations of NPs. The IR spectrum of this foamy top layer evidences the high amount of SiO2 bonds suggesting the clustering of the NPs into this layer linked by the nitrate ions. The linking is enhanced by the presence of hydroxyls in the NPs’ surface (i.e., hydroxilated NPs) that once mixed in the NF suffer ionic exchange between OH− and NO3 − species, leading to O2–Si–O–NO2 species at the interface where a thermal boundary resistance or Kapitza resistance appears (RT = 2.2 m2 K kW−1). Moreover, the presence of an exothermic reactive processes in the calorimetry of the mixture with 1 wt% of NPs evidences a reactive process (ionic exchange). These factors contribute to the heat capacity increase and thus, they explain the anomalous behavior of the heat capacity in nanofluids.Adela Svobodova-SedlackovaAlejandro CalderónCamila BarrenechePablo GamalloA. Inés FernándezNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-10 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Adela Svobodova-Sedlackova Alejandro Calderón Camila Barreneche Pablo Gamallo A. Inés Fernández Understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization
description	Abstract Nanofluids (NFs) are colloidal suspensions of nanoparticles (NPs) within a base fluid. Unlike conventional mixtures, NFs exhibit dramatically enhanced properties, such as an abnormal increase in heat capacity at low concentration of NPs (e.g., Cp values 30% higher than the base material value). Understanding the thermo-physical behavior of NFs is essential for their application as thermal energy storage systems. In this study, we analyze a sodium nitrate ionic system containing 1 wt%, 3 wt% and 7 wt% of SiO2 NPs with different techniques like infrared thermography, infrared spectroscopy and differential scanning calorimetry (DSC) in order to shed light on the mechanism behind the increase of Cp. The themographies reveal the presence of a colder layer on top of the NF with 1 wt% of NPs whereas this layer does not appear at higher concentrations of NPs. The IR spectrum of this foamy top layer evidences the high amount of SiO2 bonds suggesting the clustering of the NPs into this layer linked by the nitrate ions. The linking is enhanced by the presence of hydroxyls in the NPs’ surface (i.e., hydroxilated NPs) that once mixed in the NF suffer ionic exchange between OH− and NO3 − species, leading to O2–Si–O–NO2 species at the interface where a thermal boundary resistance or Kapitza resistance appears (RT = 2.2 m2 K kW−1). Moreover, the presence of an exothermic reactive processes in the calorimetry of the mixture with 1 wt% of NPs evidences a reactive process (ionic exchange). These factors contribute to the heat capacity increase and thus, they explain the anomalous behavior of the heat capacity in nanofluids.
format	article
author	Adela Svobodova-Sedlackova Alejandro Calderón Camila Barreneche Pablo Gamallo A. Inés Fernández
author_facet	Adela Svobodova-Sedlackova Alejandro Calderón Camila Barreneche Pablo Gamallo A. Inés Fernández
author_sort	Adela Svobodova-Sedlackova
title	Understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization
title_short	Understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization
title_full	Understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization
title_fullStr	Understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization
title_full_unstemmed	Understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization
title_sort	understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/8836eed336394689b84721119ee1629e
work_keys_str_mv	AT adelasvobodovasedlackova understandingtheabnormalthermalbehaviorofnanofluidsthroughinfraredthermographyandthermophysicalcharacterization AT alejandrocalderon understandingtheabnormalthermalbehaviorofnanofluidsthroughinfraredthermographyandthermophysicalcharacterization AT camilabarreneche understandingtheabnormalthermalbehaviorofnanofluidsthroughinfraredthermographyandthermophysicalcharacterization AT pablogamallo understandingtheabnormalthermalbehaviorofnanofluidsthroughinfraredthermographyandthermophysicalcharacterization AT ainesfernandez understandingtheabnormalthermalbehaviorofnanofluidsthroughinfraredthermographyandthermophysicalcharacterization
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Understanding the abnormal thermal behavior of nanofluids through infrared thermography and thermo-physical characterization

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