Scientific Results

Carbon-nanohorn based nanofluids for a direct absorption solar collector for civil application

Year: 2015

Authors: Moradi A., Sani E., Simonetti M., Francini F., Chiavazzo E., Asinari P.

Autors Affiliation: Energy Department, Politecnico Di Torino, Corso Duca Degli Abruzzi 24 10129, Torino, Italy
National Institute of Optics, National Research Council (CNR-INO), Largo E. Fermi 6, 50125, Firenze, Italy

Abstract: Direct solar absorption has been often considered in the past as a possible solution for solar thermal collectors for residential and small commercial applications. A direct absorption could indeed improve the performance of solar collectors by skipping one step of the heat transfer mechanism in standard devices and having a more convenient temperature distribution inside the collector. Classical solar thermal collectors have a metal sheet as absorber, designed such that water has the minimum temperature in each transversal section, in order to collect as much solar thermal energy as possible. On the other hand, in a direct configuration, the hottest part of the system is the operating fluid and this allows to have a more efficient conversion. Nanofluids, i.e., fluids with a suspension of nanoparticles, such as carbon nanohorns, could be a good and innovative family of absorbing fluids owing to their higher absorption coefficient compared to the base fluid and stability under moderate temperature gradients. Moreover, carbon nanohorns offer the remarkable advantage of a reduced toxicity over other carbon nanoparticles. In this work, a three-dimensional model of the absorption phenomena in nanofluids within a cylindrical tube is coupled with a computational fluid dynamics (CFD) analysis of the flow and temperature field. Measured optical properties of nanofluids at different concentrations have been implemented in the model. Heat losses due to conduction, convection and radiation at the boundaries are considered as well.

Journal/Review: JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY

Volume: 15 (5)      Pages from: 3488  to: 3495

More Information: Authors thank Dr. Simona Barison, Dr. Cesare Pagura and Dr. Filippo Agresti for preparing nanofluids; Mr. Massimo D’Uva and Mr. Mauro Pucci for technical assistance. P. Asinari and E. Chiavazzo acknowledge the support of the Italian Ministry of Research (FIRE grant RBFR10VZUG, THERMALSKIN project, www.thermalskin.org/)
KeyWords: Carbon; Carbon nanotubes; Computational fluid dynamics; Heat transfer; Nanohorns; Nanoparticles; Optical properties; Sheet metal; Solar collectors; Solar energy; Solar heating; Suspensions (fluids); Temperature, Absorption co-efficient; Carbon nanohorn; Commercial applications; Computational fluid dynamics analysis; Direct absorption; Heat transfer mechanism; Nanofluids; Solar thermal collector, Nanofluidics
DOI: 10.1166/jnn.2015.9837

Citations: 35
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