Experimental investigation of the hydro-thermal efficiency of the non-Newtonian ferrofluid in the annulus heat tube under the influence of the non-uniform magnetic fields

Background

Annulus heat pipes, employed in concentric pipe heat exchangers, attracted extensive application in chemical laboratories due to their unique characteristics in design, adaptability, convenient manufacturing, and size. However, as modern industries require enhanced heat transfer capabilities, numerous investigations have been conducted over the past few decades to examine the thermal performance of annulus space. While previous research demonstrated the considerable impact of an external magnetic field in enhancing the thermal efficiency of heat pipes and heat exchangers, the specific influence of both magnetic field and non-Newtonian fluid within an annulus pipe remained uncertain.

Method

In this study, an experimental investigation was carried out to examine the hydrothermal behavior of a non-Newtonian ferrofluid within an annulus space, while being subjected to a non-uniform external magnetic field. The working fluid used was a mixture of water and 2 % Carboxymethyl cellulose (CMC), which exhibits non-Newtonian properties. Ferrofluids were prepared by incorporating varying proportions of Fe3O4 into the base flow. The study focused on analyzing the influence of the magnetic field, magnetic field intensities, the number of magnetic sources, and the Reynolds number.

Significant Findings

The results revealed a significant improvement of approximately 71 % in average heat transfer within the channel when the magnetic field was employed at low Reynolds numbers (Re=200) with a magnetic field intensity of 400 G, and a single electromagnet was activated. However, at Re=500 and B = 400 G, with only one electromagnet activated, the improvement in heat transfer was approximately 55 %. Moreover, a numerical simulation is performed on the geometry to better clarify the physics of the fluid in the domain.