Convective heat transfer enhancement of the Water-based magnetite nanofluids in the presence of a 3-D low-intensity magnetic field

International Journal of Nano Dimension

مقاله 5، دوره 6، شماره 2، تیر 2015، صفحه 141-151   

نوع مقاله: Reasearch Paper

شناسه دیجیتال (DOI): 10.7508/ijnd.2015.02.004

نویسندگان

E. Esmaeili^{* 1}؛ R. Ghazanfari²؛ S. Farsad²

¹Birjand University of Technology, Department of Chemical Engineering, P.O. Box 97175/569, Birjand, Iran.

²Birjand University of Technology, Department of Mechanical Engineering, P.O. Box 97175/569, Birjand, Iran.

چکیده

In the current investigation, Fe₃O₄ water-based nanofluids were synthesized to examine the effect of an alternative 3-D external magnetic field on its thermal behavioral pattern. A solvothermal method was used to prepare the magnetite nanoparticles. To characterize the nanoparticles, the study employed transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometer and zeta-potential experiments. Vibrating sample magnetometer evaluations thoroughly confirmed the super-paramagnetic characteristics of the nanoparticles. Therefore, exposition of the resulting nanofluids to an AC external magnetic field led to the formation of aligned dipoles parallel to the applied field. Afterwards, the net magnetization in the absence of the external field was set to zero. Thermal measurements demonstrated an enhancement of convective heat transfer coefficients, particularly in the case of more diluted samples. The highest value of h was associated with the most diluted sample, where the h value was two times greater than that in the base fluid at V=1.4 V. This was attributed to the augmentation of both the Brownian motions and the viscosity gradients in the centerline of the test section.

کلیدواژه‌ها

External magnetic field؛ Convective heat transfer؛ nanofluid؛ Magnetite؛ Magnetization