Journal
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
Volume 39, Issue 4, Pages 556-564Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.icheatmasstransfer.2012.02.008
Keywords
Heat transfer; Nanofluid; Uniform wall temperature; Helical and straight tubes; Experiments
Categories
Funding
- National Iranian Oil Products Distribution Company (NIOPDC)
- Iran Nanotechnology Initiative Council (INIC)
- Iranol Oil Company
- College of Engineering, University of Tehran
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In this study, heat transfer enhancement of a nanofluid flow inside vertical helically coiled tubes has been investigated experimentally in the thermal entrance region. The temperature of the tube wall was kept constant at around 95 degrees C to have isothermal boundary condition. Experiments were conducted for fluid flow inside straight and helical tubes. In these experiments, the effects of a wide range of different parameters such as Reynolds and Dean numbers, geometrical parameters and nanofluid weight fractions have been studied. In order to investigate the effect of the fluid type on the heat transfer, pure heat transfer oil and nanofluids with weight concentrations of 0.1, 0.2 and 0.4% were utilized as the working fluid. The thermo-physical properties of the working fluids were extremely temperature dependent; therefore, rough correlations were proposed to predict their properties. Based on the experimental data, utilizing helical coiled tubes instead of straight ones enhances the heat transfer rate remarkably. Besides, nanofluid flows showed much higher Nusselt numbers compared to the base fluid flow. Finally, it was observed that combination of the two enhancing methods has a noticeably high capability to the heat transfer rate. (C) 2012 Elsevier Ltd. All rights reserved.
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