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Corresponding Author

Tolba, Ahmed

Subject Area

Mechanical Power Engineering

Article Type

Original Study

Abstract

In this paper, the effects of constant, alternating and rotating magnetic fields on the laminar forced convective heat transfer of /water nanofluid (ferrofluid) in a uniformly heated copper tube are investigated experimentally. The local convective heat transfer coefficients are measured in the hydrodynamically fully developed region. The experiments are conducted using ferrofluid with 2.5% mass concentration. A quadrupole magnetic field system has been designed and constructed to generate the constant, alternating and rotating magnetic fields. For the magnetic field system, different operation modes were also examined and the most efficient mode was obtained. The effects of alternating magnetic field frequency and rotating magnetic field speed were also studied. The primary experiments showed that Uni-pole magnetic field system provides the maximum heat transfer enhancement. A significant enhancement in the local convective heat transfer of ferrofluid was observed by application of constant magnetic field. It was observed that constant magnetic field has provided a maximum local heat transfer enhancement of 119.6% compared to the case without magnetic field for ferrofluid with 2.5% mass concentration and at Re = 2000. This value is decreased to 106.7% and 96.8% by application of rotating and alternating magnetic field, respectively. Additionally, increasing the alternating magnetic field frequency and the rotating magnetic field speed adversely affect the heat transfer enhancement.

Keywords

Ferrofluid; Forced convection; heat transfer enhancement; Constant magnetic field; Alternating magnetic field; Rotating magnetic field

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