Nonmagnetic fluids

During the flow of gas and liquid throughout the bed, the Kelvin force affects the fluids differently depending on their respective magnetic susceptibihty values. By orienting this force vertically, a directional control can be exerted on the flow achieving thus artificially micro- or macrogravity conditions  

In the case of trickle flow, it has been shown that under certain conditions the slit-flow approximation yields a very satisfactory set of constitutive equations for the gas-liquid and the liquid-solid drag forces [20, 21]. As a matter of fact, the slit flow becomes well representative of the trickle-flow regime when the liquid texture is contributed by solid-supported liquid Aims and rivulets. This generally occurs at low liquid flow rates that allow the transport of film-like liquids [20]. We will assume, without proof though, that such hypotheses also hold in the case of artificial-gravity operation. The validity of these assumptions and of the several others outlined above will be evaluated later in terms of model versus experiment comparisons. Choosing the drag force closures of the simplified Holub slit model [20], the equations system becomes  

Note that in Eqs. (11.7) and (11.8), the Galileo numbers use the corresponding artificial-gravity values for liquid and for gas phase. 

Equations (11.7)-(11.9) are an adapted form of the slit model of Holub et al. [20] to a trickle bed experiencing artificial-gravity conditions. 

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Compared with a nonmagnetic fluid, the Navier-Stokes equation (4) for ferrofluid flow in a microchannel has an additional term for the magnetic force [1] ... 

Figure 2.12 Exploded (left) and assembled (right) view of a toroid cavity autoclave probe for in situ investigations under high gas pressures or in supercritical fluids. Autoclave base (A) and autoclave body (P-bronze, B) thermocouple (C) coaxial heater (D) PTFE ring (E) central conductor (Cu/Be ring, F) nonmagnetic pin from male coaxial connection (G) RF feedthrough (from Rathke [28], H) base-plate (MACOR, I) fixing screws (P-bronze, J) PEEK capillary (l<) ceramic ball (Si3N4, L) PTFE seal (M).

The separator can either be operated wet, treating a slurry, or dry, treating a fine powder. In the wet mode, the fluid drag provides the separating force between the magnetic contaminants and the nonmagnetic medium. In the dry mode, the matrix is vibrated. This fluidises the fute material as it floiA s through the matrix. 

A ferrofluid is a liquid consisting of ferromagnetic nanoparticles suspended in a nonmagnetic carrier fluid, typically water or oil. The ferromagnetic nanoparticles are coated with a surfactant such as oleic acid to prevent their agglomeration. The magnetic particles have typical diameters on the order of 5-15 nm and a volume fraction of about 5-10 %. 

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