Convective heat transfer enhancement in a double pipe mini heat exchanger by magnetic field induced swirling flow

In this paper, an innovative method has been proposed that improves the convective heat transfer in heat exchangers and also reduces the pressure drop penalty compared to the other conventional enhancement techniques. The method is based on applying an external magnetic field to generate a swirling flow in the magnetic working fluid. A three dimensional numerical simulation has been carried out to investigate the performance of the presented method in a double pipe mini heat exchanger at different concentrations and flow rates of the magnetic nanofluid, and magnetic field intensities. Results show that application of the external magnetic field augments the heat transfer enhancement up to 320% with only a slight increase of the pressure drop. The induced swirling flow improves the heat transfer rate by disrupting the thermal boundary layer and increasing the flow mixing in the heat exchanger. Moreover, flow resistance and consequently the pressure drop is minimized due to the lack of any additional obstacle in the flow passage. It is concluded that the favorable conditions for the mini heat exchanger operation are low Reynolds numbers, high magnetic field intensities, nd high concentrations of the nanofluid.