Magnetocaloric Fluids - Magnetocaloric Energy Conversion: From Theory to Applications - page 174

yield stress. With an increased shear rate ferro uids can show Newtonian and shear

thinning behaviour. The Casson model (Eq. 5.16) considers the yield stress as well
as the shear thinning behaviour. The same is also true for the Herschel

fl

Bulkley
model (Eq. 5.17). Note that the yield stress is associated with the particle size, the
volume fraction and the magnetic

-

eld. The higher these are, the higher will be the
yield stress. This also depends on the potential agglomeration of the particles.

Title Magnetic nano fl uid properties and some applications (V é k á s[ 33 ])

Materials used for
investigation

Magnetic fluids based on Fe 3 O 4 nanoparticles

Viscosity Vand ' s equation (Eq. 5.6), and the equation given by Krieger and

Dougherty [ 34 ]

Title Field-induced rotational viscosity of a ferrofluid: effect of capillary

size and magnetic eld direction (Andhariya et al. [ 35 ])

Materials used for
investigation

Nanomagnetic particles of iron ferrite in water and kerosene-based
ferro uids. The particles were coated with a bi-layer of surfactant.

For the kerosene-based ferro

fl

uid the magnetite particles were coated
with a single layer of surfactant and dispersed in kerosene. The
volume fraction of particles in the water-based magnetic

fl

fl uid was

0.64 %, while in the kerosene-based magnetic uid the particles had

a volume fraction of 2.24 %. The average particle diameter was
10.4 nm. The work is concentrated into eld-induced rotational
viscosity when a ferro

fl

fl uid fl ows through a capillary placed in a

magnetic eld

Viscosity The authors considered the rotational viscosity by Shliomis

(Eq. 5.23 )

Title Design method for automatic energy transport devices based on the

thermomagnetic effect of magnetic fl uids (Lian et al. [ 36 ])

Materials used for
investigation

A kerosene-based Mn - Zn ferrite magnetic fluid with a saturation
magnetization of 6.5 × 10 4 Am − 1 . The average diameter of the
suspended magnetic particles was about 6.8 nm and the volume
fraction of the ferrite magnetic nanoparticles was 0.045

Viscosity The authors applied Einstein s equation (Eq. 5.2 ), which they

extended with a linear form to account for the in

'

uence of the
magnetic eld on the viscosity. Using a combination of two
equations they proposed a new equation, which takes into account
the in

fl

fl uence of the magnetic eld

Title Influence of large size magnetic particles on the magneto-viscous

properties of a ferrofluid (Shah et al. [ 32 ])

Materials used for
investigation

Three ferro uid contained

magnetite particles with an average size of 10 nm dispersed in
transformer oil. The second

fl uids were investigated. The rst ferro fl

fl uid, denoted by authors as the

magnetorheological uid, consisted of large magnetite particles,

having a 30-nm particle size dispersed in transformer oil. The third
fl

fl

uid was labelled as the nano- magnetorheological fl uid and

represented a mixture of the rst and the second uid in different

weight proportions. The particles were coated with oleic acid
surfactant and dispersed in transformer oil. The magnetic eld was
increased from 0 to 1 T

fl