Enhanced thermal conductivity by the magnetic field in heat transfer nanofluids containing carbon nanotube

In this paper, we report for the first time that the thermal conductivity (TC) of the heat transfer nanofluids could be enhanced by the external magnetic field. The heat transfer nanofluids contain carbon nanotubes (CNTs) and magnetic-field-sensitive nanoparticles of Fe(2)O(3). The reasonable explanation for these interesting results is that the Fe(2)O(3) particles form aligned chains under applied magnetic field and help to connect the nanotubes, which results in improved thermal conductivity. On longer holding in magnetic field, the particles gradually move and form large clumps of particles, causing clumping of CNTs, then decreasing the TC. We also found that the time to reach the maximum peak value of TC is increased as the applied magnetic field is reduced by increasing the gap between two magnets. Scanning electron microscopy (SEM) pictures show that the nanotubes and nanoparticle are aligned well under the influence of magnetic field. (c) 2007 Elsevier B.V. All rights reserved.