Magnetocaloric Fluids - Magnetocaloric Energy Conversion: From Theory to Applications - page 164

Chapter 5
Magnetocaloric Fluids

Magnetocaloric fl uids represent a class of magnetic fl uids that can generally be

subdivided into two main categories, i.e. ferro uids)

and magnetorheological (MR) fluids. The general characteristic of all these fluids is
that they change their physical properties when exposed to an external magnetic

fl uids (FF) (or magnetic nano fl

uids are suspensions of magnetic nanoparticles dispersed in certain
base liquids. Magnetorheological

eld. Ferro fl

uids are particle suspensions of micron-sized
particles consisting of a magnetic material dispersed in a carrier liquid. The size
difference between the particles in ferro

fl

fl uids and the particles in magnetorhe-

ological uids results in the most important differences concerning the properties

and the behaviour of these

fl

uids.
There was not much experimental work done in the domain of magnetocaloric

fl

fl uids. On the other hand, a variety of studies and applications can be found in the

more general

eld of ferro fl uids and magnetorheological fl uids. Therefore, we will

take advantage of these studies and brie fl y describe models that can be applied for

magnetocaloric fl uids as well. Since both magnetocaloric ferro fl uids and magnet-

ocaloric magnetorheological fl uids are viscous, Newtonian and/or non-Newtonian

fl ow properties relates to the rhe-

ology. Therefore, we begin the chapter with the rheology of magnetic

uids, an important feature that concerns their fl

uids and the
various rheological, constitutive models. Then we introduce the equations that
relate to the thermo-magneto

fl

uids. Since this concerns
complex investigations and the aim of this topic is to provide information that may
serve for a basic understanding, we also refer to the literature that may give the most
comprehensive overview of the phenomenon of ferro

- fl uid dynamics of such fl

uid-dynamics. In addition, a
review of the existing studies and applications of magnetocaloric

fl

uids has been
performed. At the end of the chapter, a discussion and guidelines are given on the
potential design of devices that concern magnetocaloric energy conversion.
Note that this chapter may provide important information also for the application
of magnetic

fl

uids that may also be successfully applied in magnetocaloric energy
conversion as the heat transfer

fl

uids. Moreover, a smart design of magnetocaloric
devices with the application of magnetic

fl

uids can bring new solutions for valve
systems, sealing elements, thermal diode mechanisms or even the parts of

fl

fl uid

propulsion systems (pumps).