Wetting dynamic

TABLE 20-37 Methods of Characterizing Wetting Dynamics of Particulate Systems ... 

Wet Dynamic Orifice Types 1 —2 1 —5 Note 1 23 —6 3 to 1 10—40 Small Small Note 1 As cfm or less No Varies with 1 design / None Unlimited... 

Figure 19. The Washburn Test for measuring wetting dynamics.

Here, the dynamic liquid holdup (in m3/m3) refers to the portion of the void (available) bed volume that has been occupied by the liquid. There are also correlations for the static holdup, that is, when the flow rate is zero after wetting. Dynamic liquid holdup is normally between 0.03 and 0.25, whereas the static liquid holdup is between 0.01 and 0.05, and for nonporous catalysts, usually he s < 0.05 (see Section 3.6.3 Perry and Green, 1999). 

The entropic arguments have been used to explain many unusual phenomena, such as dewetting of polymer brushes by the melt of the same polymer [301 ] and enrichment of the surface with lower molecular weight component [302], which are not observed for simple liquids. Also wetting dynamics is strongly af-... 

Figure 21. Wetting dynamics of water at the solid surface with gap (graphite) of 7.4 A (gray) and no gap (black) between the catalyst and membrane. Both the systems show a similar trend of increase in wetting with the water content.

A quantitative analysis of the wetting dynamics can be done by the recording the number of water molecules adsorbed on to the catalyst surface as a function of time. Figure 21 shows the wetting dynamics with no gap (system IV) and a gap of 7.4 A and it can be obviously seen that wetting has dramatically lowered in the presence of even a small gap (7.4 A). " ... 

Wet Dynamic Scrubbers. These scrubbers are also known as mechanical scrubbers, as seen in Figure 20.7. They have a power-driven rotor to produce a spray that is centered in the inlet of the unit such that the blades of the rotor are coated with water. As the dust-laden stream enters, it contacts the water surfaces and the dust-water mixture is thrown outward against the walls. 

Fig. 20 Evolution of the relaxation time r (deduced from the width of the rim and the de wetting dynamics) as a function of molecular weight together with the evolution of bulk reptation times. Xd is the reptation time representing the longest relaxation time of a polymer of molecular weight M. The film thickness was set at 100 nm...

This treatment does not take the interactions of the fluid with the substrate into account. Wetting considerations lead to an unusual surface profile and to hydrodynamic instabilities as discussed in Chapter 4 in the section on wetting dynamics. ... 

Joshi, A., Sun, Y. Wetting dynamics and particle deposition for an evaporating colloidal drop a lattice Boltzmann study. Phys. Rev. E 82, 041401 (2010)... 

When discussing wetting dynamics, the dynamic contact angle 0 is the central parameter. In the so-called capillary regime, spreading is promoted by the in-plane and out-of-balance interfacial tension force, which often is expressed as follows ... 

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