THERMAL SCIENCE

International Scientific Journal

HEAT TRANSFER CHARACTERISTICS OF AL2O3/WATER NANOFLUID IN LAMINAR FLOW CONDITIONS WITH CIRCULAR RING INSERT

ABSTRACT
In this experimental investigation convective heat transfer, friction factor, and thermal enhancement characteristics of straight circular duct fitted with circular ring insert of constant heat flux boundary condition under fully developed laminar flow is presented. Tests have been conducted by using 0.1% volume concentration of Al2O3 nanofluid and water. Inserts of different pitch to diameter ratios of 6.25, 8.33, 12.5, and 16.67 with center core rod were used for this investigation. The circular ring insert shows a superior thermal performance than plain tube. The experimental results demonstrated that the Nusselt number, friction factor, and thermal enhancement factor increases with decrease in pitch to diameter ratio. The circular ring inserts of lower pitch to diameter ratio of 6.25 with nanofluid increases the Nusselt number by 165.38% compared to pure water and the friction factor, found to be 7.89 times higher than that of water. Empirical correlations are develope for Nusselt number and friction factor in terms of Reynolds number, volume concentration, and pitch ratio. The thermal performance factor was found to be greater than unity for all pitch to diameter ratios.
KEYWORDS
PAPER SUBMITTED: 2015-09-06
PAPER REVISED: 2016-01-03
PAPER ACCEPTED: 2016-02-29
PUBLISHED ONLINE: 2016-11-13
DOI REFERENCE: https://doi.org/10.2298/TSCI16S4159M
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2016, VOLUME 20, ISSUE Supplement 4, PAGES [S1159 - S1168]
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© 2018 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence