Effect of magnetic field on the mixed convection $$\hbox {Fe}_{3}\hbox {O}_{{{4}}}/\hbox {water}$$
- PDF / 1,243,181 Bytes
- 12 Pages / 595.276 x 790.866 pts Page_size
- 56 Downloads / 268 Views
© Indian Academy of Sciences
Effect of magnetic field on the mixed convection Fe3 O4 /water ferrofluid flow in a horizontal porous channel AMIRA JARRAY, ZOUHAIER MEHREZ∗ and AFIF EL CAFSI Laboratoire d’Energétique et des Transferts Thermique et Massique (LETTM), Département de Physique, Faculté des Sciences de Tunis, Université d’el Manar, Tunis, Tunisia ∗ Corresponding author. E-mail: [email protected]; [email protected] MS received 7 May 2020; revised 11 July 2020; accepted 29 July 2020 Abstract. The effect of an external magnetic field on the mixed convection Fe3 O4 /water ferrofluid flow in a horizontal porous channel was studied numerically. The governing equations using the Darcy–Brinkman– Forchheimer formulation were solved by employing the finite volume method. The computations were carried out for a range of volume fractions of nanoparticles 0 ≤ ϕ ≤ 0.05, magnetic numbers 0 ≤ Mn ≤ 100, Reynolds numbers 100 ≤ Re ≤ 500, Darcy numbers 10−3 ≤ Da ≤ 10−1 and porosity parameters 0.7 ≤ ε ≤ 0.9 while fixing the Grashof number at 104 . Results show the formation of recirculation zone in the vicinity of the magnetic source under the influence of Kelvin force. It grows as the magnetic number increases. The friction factor increases by increasing the magnetic number and diminishes with the increase in Darcy number. The flow accelerates as the magnetic field intensifies. The heat transfer rate increases by increasing the volume fraction of the nanoparticles and the magnetic number. The effect of magnetic field on the hydrodynamic and thermal behaviours of the ferrofluid flow considerably intensifies by increasing Reynolds number and Darcy number. The combined effect of ferromagnetic nanoparticles and magnetic field on the enhancement rate of heat transfer becomes more pronounced at high values of Reynolds number, permeability and/or porosity parameter. Keywords. Mixed convection; porous medium; ferrofluid; magnetic field. PACS Nos 44.15.+a; 44.25.+f; 44.27.+g; 47.65.Cb
1. Introduction Several techniques are there to increase heat transfer in engineering applications using cooling and heating systems such as electronic and microelectronic devices, heat exchangers, engines and automobiles, solar energy, refrigerator-freezers, nuclear reactors and transformers. The most recent technique is the one where thermal conductivity of the carrier fluid is increased by adding nanosized metallic or metallic oxide particles. The obtained suspension, called nanofluid, has shown its effectiveness in terms of heat transfer enhancement in many engineering configurations. When the suspended nanoparticles are magnetisable, a particular nanofluid called ferrofluid is obtained. Apart from its improved thermophysical properties, the heat transfer and the ferrofluid flow behaviour can be modified by applying external non-uniform magnetic field. In fact, under the effect of magnetic field, the magnetic moments of the particles follow the field lines, leading to the 0123456789().: V,-vol
modification of the flow field and th
Data Loading...
