Effect of the non-electrically conductive spindle on the viscosity measurements of nanofluids subjected to the magnetic field

The viscosity measurements of magnetic nanofluid subjected to the magnetic field are indispensable in various heat transfer studies. Intention of the present discussion is to critically analyze the magnetic field's influence on the working of two viscometers; a Glass capillary viscometer and a DV-E Brookfield viscometer. The novelty of the present study is in the identification of the underlying reason for the massive escalation in viscosity when the magnetic nanofluid is subjected to magnetic field and rectification of the error caused. The stainless-steel spindle in the viscometer is replaced with a non-electrically and non-magnetically conductive nylon spindle to rectify the error. The dynamic viscosity of magnesium ferrite nanofluid of different volume fractions at a temperature of 25 °C in the occurrence of magnetic field was measured. The viscosity of magnetic nanofluid measured using DV-E Brookfield viscometer escalated to a maximum of 725% over the same measured using glass capillary viscometer with the magnetic field application. The application of the nylon spindle in the viscometer eliminates the error caused due to the eddy current formation in the spindle. Therefore, this study recommends using viscometers with non-electrically and non-magnetically conductive spindles for accuracy while measuring the viscosity of magnetic fluids. [Display omitted] •Critically analyzed the impact of the magnetic field on the viscosity measurement devices.•Ferrofluid viscosity enhanced unrealistically 725% for 0.20% volume fraction of MgFe2O4 at 350 G using DV-E viscometer.•Viscosity of ferrofluid enhanced 27.68% for 0.20% volume fraction of MgFe2O4 at 350G using glass capillary viscometer.•Causes for the deviation in viscosity is identified and rectified.•A new spindle for viscosity measurement is fabricated and tested.