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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Heat Transfer Enhancement in Tangential Injection Induced Swirl Flows

Get access (open in a dialog) DOI: 10.1615/IHTC15.hte.008801
pages 4171-4183

摘要

Inducing swirls is an attractive approach to enhancing heat transfer in both single- and two-phase internal flows. The ability to vary the tangential and axial flow rates and maintain optimal performance as the heat load varies is a unique feature of this enhancement technique. As a first step towards developing heat transfer enhancement techniques applicable to high temperature concentrated solar power (CSP) systems, we develop an intermediate temperature (up to 400 °C) flow loop designed to experimentally investigate heat transfer enhancement due to tangential injection-induced swirl flows. This swirl generation method was suggested to yield the highest enhancement in heat transfer on a constant pumping power basis. A commercially available heat transfer fluid (Dowtherm A) is used as the working fluid for measurements over temperature ranging from 25 to 250 °C. The effect of such parameters as Reynolds number (Re: 1,400 – 40,000), Prandtl number (Pr: 7 – 43) and the ratio of tangential momentum flux to total momentum flux (Mt/MT: 0 – 9) on heat transfer enhancement are investigated. For given Re and Pr, heat transfer enhancement increases with increase in the momentum flux ratio. For given conditions, lower values of Pr yield higher heat transfer enhancement. Compared with purely axial flow, the average Nusselt number is enhanced by up to 250% and local Nusselt number by up to a factor of 8. The pressure drop increases quite rapidly with tangential injection, and, on a constant pumping power basis, the average heat transfer is enhanced by a factor of 1.1 – 2.6. The experimental data collected in this study shows that this heat transfer enhancement technique works better at higher temperatures, when Pr is low. The data from this work can help in the design of enhanced high temperature heat transfer flow loops with low Pr fluids for power generation and other applications.