Experimental Investigation of a U-Tube Performance Using Nanoferrofluids Under the Effect of Magnetic Fields

Abstract

The effects of nanoferrofluids on the overall performance of curved tubes (with various radii of curvature) are experimentally investigated under the influence of constant and alternating magnetic fields. The working fluids are distilled water and a ferrofluid (Fe3O4/water) with 0.2% and 0.4% volume concentrations. The experiments are performed under a constant wall heat flux (≈12,700 W/m2) using a chrome–nickel electric heater element insulated by refractory fabrics. The mass flowrate is varied from 0.2 to 0.7 kg/min. There are three key parameters, namely, type of the magnetic field, volume of concentration of nanoparticles, and radius of curvature of the pipes that affect the hydrodynamic and thermal characteristics of the system, but the latter is comparatively the dominant factor. If the Reynolds number is 930 in the pipe of 0.2-m diameter of curvature, and also a 50-Hz alternating magnetic field is applied to the curved pipe, the results reveal that using a 0.4% ferrofluid, Nusselt number is improved by 32% compared to that of the distilled water. Nevertheless, due to the undesirable influence of pressure gradient, the best overall effectiveness of 1.12 is attained in the circumstances but in the pipe of 0.4-m diameter of curvature.