Magnetocaloric Fluids - Magnetocaloric Energy Conversion: From Theory to Applications - page 189

A review of different correlations useful for suspensions, including nano fl uids

and magnetic uids, can be found in Nkurikiyimfura et al. [ 103 ], Kaviany [ 106 ],

Kandula [ 107 ], Kleinstreuer and Feng [ 108 ], Wang and Mujumdar [ 109 ] and Singh
[ 110 ].
Besides the particle shapes and packing formations, researchers also evaluated
the in

fl

uence on the effective conductivity of other physical properties and
parameters. This is especially so when considering nano

fl

fl uids. For instance, Das

et al. [ 111 ] investigated the in uids. They

observed a strong increase in the effective thermal conductivity with the increased
temperature, which could be a consequence of the kinetics of molecules and solid
nanoparticles. This was also con

fl uence of temperature in the case of nano fl

rmed by Abareshi et al. [ 112 ].
However, as denoted by Kleinstreuer and Feng [ 108 ], a large number of
researchers did not

nd the strong dependence of the effective thermal conductivity
on the temperature. Therefore, the dependence of the effective thermal conductivity
on temperature stays an open eld for future research efforts. Kleinstreuer and Feng

[ 108 ] also reviewed the measuring techniques for effective thermal conductivity in
nano uids.

Some researchers have also investigated the in

fl

fl uence on the effective thermal

conductivity by pH value, the type of the base uid, the nanoparticle shape, the

degree of nanoparticle dispersion/interaction, and various additives (see, e.g., Wang
and Choi [ 113 ], Li and Peterson [ 114 ], Zhu et al. [ 115 ], Jang and Choi [ 116 ],
Timoefeva et al. [ 117 , 118 ], Murshed et al. [ 119 ]).
Based on the existing research, we can conclude that the thermal conductivity of
magnetic

fl

fl uids (nano fl uids or magnetorheological fl uids) will depend not only on

the basic parameters, de ned in Eq. ( 5.62 ), but will also take into account the

following dependencies:

Effect of Brownian-motion (ferro uids only) (see also Lee et al. [ 120 ], Wang

et al. [ 113 ], Keblinski et al. [ 121 ], Jang and Choi [ 122 ], Kleinstreuer and Li
[ 123 ], Prasher [ 124 ], Li [ 125 ], Kumar et al. [ 126 ], Koo and Kleinstreuer [ 127 ],
Bao [ 128 ], and Feng and Kleinstreuer [ 129 ]),

fl

￿

Effect of magnetic eld as well as the related anisotropy of the effective thermal

conductivity (see, e.g. Blums [ 130 ], Xuan and Wang [ 131 ], Kirchler and
Odenbach [ 132 ], Philip et al. [ 133 , 134 ], Wright et al. [ 135 ], Wensel et al. [ 136 ],
Shima et al. [ 137 ], Gavili et al. [ 138 ], Nkurikiyimfura et al. [ 139 ] (note stronger
effects can be expected in magnetorheological

￿

fl uids),

￿ Effect of surfactants,

￿ Effect of particle size and shape including potential agglomeration or clus-

tering effects (see, e.g. Odenbach [ 18 ], Keblinski et al. [ 140 ], Keblinski [ 141 ],
Eapen et al. [ 142 ], Prasher et al. [ 143 ], Tillman and Hill [ 144 ], Wang et al.
[ 145 ], Tillman and Hill [ 146 ], Wang and Fan [ 147 ], Bishop et al. [ 148 ],
Mendelev and Ivanov [ 149 ]),

Effect of temperature, which can also affect the magnetic properties of mag-
netic

￿

fl uids in the presence of a magnetic eld (not to be misunderstood as the

magnetic convection effect).