Magnetic fluid rheology and flows

Numerical Investigation on Heat and Flow Characteristics of Temperature-Sensitive Ferrofluid in a Square Cavity

“…In addition, the heat transfer of the ferrofluid in the tested cavity under magnetic intensity ( = 15000 A/m) increased greatly with the rise of the magnetic volume fractions from 1.2% (FF1) to 4.5% (FF4) due to the increased heat transfer. Namely, this is because the diffusive concentration gradients lead to the coupling effect between heat and mass transport as mentioned in Rinaldi et al [2] Also, the presence of the magnetic intensity tends to accelerate the fluid motion inside the tested cavity as mentioned in Grosan et al [27]. Figure 6 shows the effect of the isotherms and mean Nusselt numbers on the temperature difference between top and bottom walls of the tested cavity under the elapsed time of = 10000 seconds, magnetic intensity of = 15000 A/m, and magnetic volume fractions of 2.0% (FF2).…”

“…The ferrofluid generally consisted of magnetite nanosized particle of around 1 to 100 nm and carrier liquid such as water, oils, and hydrocarbons with the aid of surfactants in a continuous carrier phase. It can be controlled by both magnitude and direction of an external magnetic field and temperature [1][2][3][4][5][6][7][8][9][10][11][12]. In addition, because of the nanosized magnetic particles consisting of the ferrofluids and the surfactant attached to magnetic particles, the ferrofluid could be prevented from particles sticking to each other or precipitate with Brownian motion [2].…”

“…It can be controlled by both magnitude and direction of an external magnetic field and temperature [1][2][3][4][5][6][7][8][9][10][11][12]. In addition, because of the nanosized magnetic particles consisting of the ferrofluids and the surfactant attached to magnetic particles, the ferrofluid could be prevented from particles sticking to each other or precipitate with Brownian motion [2]. Therefore, the ferrofluid could be applied for various industrial fields: enhancement and depression of the heat transfer of the thermal devices, magnetic sealing, damping and bearing of machines, energy conversion system, drug delivery for disease curing, optical devices, micro-/nanofluidic devices, and so forth [3][4][5].…”

Multi-stage magnetic-fluid seals for operating in water – life test procedure, test stand and research results

“…The seal life diagrams for different motion speed values indicate that for each of the fluids can be observed a range of speed values below which a significant extension of failure -free operation period of the seal occurs. The process is probably associated with Kelvin -Helmholtz phenomenon of instability [2,3,11]. 7.…”

Life tests of a rotary single-stage magnetic-fluid seal for shipbuilding applications

“…Lack of susceptibility to mixing and high interphase surface tension may appear not sufficient factors if a magnetic-fluid (MF) seal is applied in its motion conditions or in case of sealed liquid flow, e. g. around ship propeller shaft. Relative displacement of two non-mixing together liquids results in generating surface instability at the interphase boundary [2,3], whose intensity fast increases over a limiting difference of velocity, that causes magneticfluid sweeping and loss of system sealing. Research work on operation of MF seals in liquid environment has been conducted by some research centres, however only a few relevant reports are available.…”