Convective heat transfer enhancement in a pitted microchannel by stimulation of magnetic nanoparticles

Publication date: Available online 23 February 2018 Source:Chemical Engineering and Processing - Process Intensification Author(s): Ehsan Karami, Masoud Rahimi, Neda Azimi Convective ferrofluid heat transfer in a microchannel under static (SMF) and rotating magnetic fields (RMF) has been investigated. The microchannel has a cylindrical pit in which a heat source with a constant heat flux is applied on the bottom wall. The top wall of pit is positioned next to a rotational permanent magnet that creates RMF, while it is stationary for SMF. The heat transfer characteristic results at various flow rates, magnetic field inductions (B) and nanoparticle volume fractions (ϕ = 0.1–2%) by applying RMF have been compared to those of SMF. Results depicted that using ferrofluid results in improvement of heat transfer rate compared to DI-water. However, applying SMF causes to reduction in the heat transfer characteristic. Results illustrated that RMF is more effective compared to SMF. In RMF, the influence of B and rotational speed of magnet (W) have been considered; heat transfer characteristics enhanced by increasing B and W. The effect of W more than 18 rad/s is not significant. The effect of increase in ϕ on heat transfer coefficient is also evaluated and increasing trend is observed. Maximum value of heat transfer coefficient is achieved for RMF with B = 1100 mT, W=18 rad/s and MNPs concentration of 2%. Graphical abstract
Source: Chemical Engineering and Processing: Process Intensification - Category: Chemistry Source Type: research