An empirical study on the pressure drop characteristics of nanofluid flow inside helically coiled tubes

• Published in: International journal of thermal sciences 2013-03, Vol.65, p.206-213
• Main Authors: Fakoor-Pakdaman, M., Akhavan-Behabadi, M.A., Razi, P.
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemistry; Coiling; Colloidal state and disperse state; Condensed matter: structure, mechanical and thermal properties; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Experiments; Fluid dynamics; Fluid flow; Fluids; General and physical chemistry; Heat transfer; Helical and straight tubes; MWCNT; Nanofluid; Nanofluids; Nanomaterials; Nanostructure; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Physics; Pressure drop; Theoretical studies. Data and constants. Metering; Thermal properties of condensed matter; Thermal properties of small particles, nanocrystals, nanotubes; Tubes
• ISSN: 1290-0729; 1778-4166
• DOI: 10.1016/j.ijthermalsci.2012.10.014

In this study, pressure drop characteristics of nanofluid flow inside vertical helically coiled tubes are investigated experimentally for the laminar flow regime. The temperature of the tube wall is maintained constant at around 95 °C to have isothermal boundary condition Experiments are implemented for fluid flow inside helically coiled tubes and a straight one. A wide range of various variables is taken into account. Pitch to tube-diameter ratio ranges between 1.6 and 6.1 and coil-to-tube diameter ratio varies from 14.1 to 20.5. Heat transfer oil is used as the base fluid, and Multi-Walled Carbon NanoTubes (MWCNTs) are utilized as the additive to provide the nanofluids. The working fluids are extremely temperature dependent, so rough correlations are proposed to predict their thermo-physical properties. Regarding the experimental data, utilization of helical coiled tubes instead of straight ones increases the pressure drop exponentially. Irrespective of the tube geometry in which the fluid flows, nanofluid flows show higher rate of pressure drop compared to that of the base fluid flow. Finally according to the observations, combination of the two techniques used in this study causes the pressure of the fluid flow to drop significantly along the test section. ► Pressure drop characteristics of MWCNT/heat transfer oil nanofluid flow inside helically coiled tubes are studied experimentally. ► The experiments are implemented under uniform wall temperature condition in the thermal entrance region of the laminar forced-convective tube flow. ► Helical coiled tubes and nanofluids are used simultaneously as the two heat transfer enhancement techniques. ► Simultaneous utilization of the so-called techniques increases pressure drop significantly. ► A rough empirical correlation is proposed to predict the fluid flow friction factor in terms of the Dean number, fluid properties and geometrical parameters.