Heat transfer enhancement of a fin-and-tube compact heat exchanger by employing magnetite ferrofluid flow and an external magnetic field

摘要

Compact heat exchangers as modern industrial devices are designed to improve heat recovery and saving energy processes in restricted spaces. In the current study, effect of a uniform external magnetic field with Fe3O4/water nanofluid for heat transfer enhancement of a fin-and-tube compact heat exchanger is numerically investigated. The obtained results are verified by the available experimental data to demonstrate accuracy of the present simulation. The results indicated that the local and average heat transfer coefficients increase around the tubes in the presence of an external magnetic field due to the vortex formation behind the tubes as well as the flow pattern alteration in the heat exchanger, no mention that the pressure drop increment is subtle through this variation. Also, it is figured out that employing an external magnetic field at low Reynolds numbers (approximately Re-D < 30) is much more appropriate since the heat exchanger effectiveness increases exponentially. A maximum heat transfer enhancement of 8.7% was obtained by employing 2%Vol. magnetite nanoparticles in deionized water as a coolant. This value surges up to 52.4% by applying an external magnetic field in the compact heat exchanger. Based on these results, employing an external magnetic field for heat transfer enhancement of compact heat exchangers and heat sinks designed for restricted spaces and low Reynolds numbers can be more efficient in comparison with other available methods since no pumping power for mass flow rate augmentation is required in the present approach.