On-demand augmentation in heat transfer of Taylor bubble flows using ferrofluids

Abstract

The thermo-fluidic transport characteristics of ferrofluids can be influenced by the application of a magnetic field. The magnetic manipulations of ferrofluids have been useful in augmenting heat transfer, as evident from recent investigations. In the present study, we examine a novel strategy for augmenting two-phase heat transfer and show that the magnetic manipulation of non-boiling Taylor bubble flow (TBF) of ferrofluids can provide on-demand augmentation. In an earlier investigation (DOI:10.1016/j.colsurfa.2020.124589), we had shown that the characteristics of the TBF of ferrofluids could be altered through external magnetic manipulations. As transport characteristics of TBFs primarily depend on their flow morphology, it was anticipated that such alteration would affect their thermal transport characteristics, which are examined in the present work. The generation of smaller bubbles and unit-cells through magnetic manipulations decreases the void fraction of the resulting TBF. In addition, a greater number of units participated in the heat exchange process compared to larger bubble-slug systems at any time instance. Such flow modifications cause considerable augmentation (which can go up to 100%) in two-phase heat transfer. The extent of augmentation depends on the applied magnetic field and induced magnetic force, homogeneous gas fraction, liquid film thickness/void fraction and flow morphology of the resulting TBF, which are examined in the present study. The application of ferrofluids in TBFs provides multiple benefits, such as suspension of nanoparticles with better thermal properties and additional functionality of the flow manipulations through external means. The proposed application with the suggested manipulation technique provides an effective alternative for an on-demand augmentation in two-phase heat transfer in low Reynolds number flows.