Enhancing the convective heat transfer in liquid oxygen using alternating magnetic fields

• Magnetic field actuated heat transfer of liquid oxygen was studied numerically.
• The vortex generation and shedding improved the heat transfer significantly.
• The maximum increment in heat transfer at Re = 500 and 0.5 T was 86.1%.
• The proposed method had the advantage of low additional pressure drops.

Compact heat exchangers working with liquid oxygen play a major role in the cryogenic air separation units. In this paper a novel alternating magnetic field actuated method, utilizing the paramagnetic property of oxygen, was proposed for enhancing the convective heat transfer in this kind of heat exchangers. A modeling investigation based on a rectangular channel with the proposed enhancement method was conducted by two-dimensional finite-element simulation. The effects of background magnetic field, inlet flow condition, and cascade configuration on the heat transfer were numerically analyzed. The numerical results indicated that vortices were generated and shed due to the periodically changing magnetic force. The vortex shedding caused fluctuation of the thermal boundary layer and mixing of cold and hot fluids, which significantly improved the heat transfer. At Re = 500 and B0 = 0.5 T, an increase of 86.1% in the overall Nusselt number was observed with a single steel bar, compared with the free-flow case without any enhancement. The proposed magnetic field actuated enhancement method provides a great potential for improving the heat transfer performance in liquid oxygen without leading to large pressure drops.