Effect of magnetic field on laminar convective heat transfer characteristics of ferrofluid flowing through a circular stainless steel tube
Section snippets
Abbreviations
- DLS
dynamics light scattering
- ID
inner diameter
- IR
infrared
- IRT
infrared thermography
- IONP
iron oxide nanoparticle
- OD
outer diameter
- OA-IONP
oleic acid coated iron oxide nanoparticle
- SS
stainless steel
- TEM
transmission electron microscopy
- VSM
vibration sample magnetometer
Synthesis and thermophysical properties of water-based ferrofluid
Iron oxide nano-particles (IONPs) were chemically synthesized by the co-precipitation method from an aqueous mixture of Fe3+/Fe2+ (2:1) solutions. The chemical reaction responsible for this synthesis is expressed as: Fe+2 + 2Fe+3 + 8OH−→Fe3O4 + 4H2O
After the synthesis of IONPs, oleic acid is added as a surfactant to prevent the agglomeration of IONPs. The oleic acid coated IONPs (OA-IONPs) were then dispersed in DI-water to prepare suspensions of IONPs or ferrofluids. The OA-IONPs are found to be
Simulation of magnetic flux density and magnetic force distribution
Distributions of the magnetic field and the resulting Kelvin's magnetic body force acting on the iron oxide nanoparticles of ferrofluid for the given configurations of the permanent magnets have been simulated using commercial software COMSOL–Multiphysics V4.3 (COMSOL Inc.). The magnetic flux density () and the magnetic force () distributions were simulated based on the Eqs. (8) and (9) as mentioned below. where is the magnetic flux density, μ0 is the magnetic
Variation of Nusselt number for DI-water flow
Prior to using the IR camera for estimation of local heat transfer coefficients, the bench marking exercise was performed to instill confidence in the subsequent estimation of local heat transfer coefficients of ferrofluid flow with and without the applied magnetic field. A series of experiments were performed for benchmarking the thermography technique using DI-water as the working fluid at flow rates of 20 and 40 mL/min (corresponding to Peclet numbers of 1467 and 2934 respectively) through
Mechanism of heat transfer enhancement
Many research groups (Maïga et al., 2005, Bianco et al., 2009, Kalteh et al., 2012) have discussed the mechanism by which the presence of nanoparticles (magnetic or non-magnetic) can enhance convective heat transfer coefficients relative to its base fluid. However, based on different observations it still remains as a debatable issue. One of the proposed mechanisms for heat transfer enhancement in nanofluids is the enhancement in thermal conductivity of nanofluid compared to its base fluid.
Summary and conclusions
The laminar convective heat transfer characteristics of ferrofluid flowing through a circular SS tube under constant heat flux condition and in the presence of applied magnetic field is experimentally investigated using IRT technique. The magnetic field and magnetic force distribution for different arrangement of magnets have been calculated using COMSOL simulation in order to support the experimental results. The major conclusions of the present study are as follows:
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There is no enhancement in
Acknowledgements
The authors wish to thank Mr. Mohammed Anwar (Nano-formulation laboratory, Faculty of pharmacy, Jamia Hamdard, New Delhi) for providing water based ferrofluid for conducting the experiments. The authors also thank Mr. Ram Krishna Saha (Department of Mechanical Engineering, IIT Kanpur) for helping us in conducting the COMSOL simulations reported in the present work.
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