Capillary forces factors affecting

Water Uptake. There is evidence to suggest that water uptake caused by capillary forces is the crucial factor in the disintegration process of many formulations. In such systems the pore structure of the tablet is of prime importance and any inherent hydrophobicity of the tablet mass will adversely affect it. Therefore, disintegrants in this group must be able to maintain a porous structure in the compressed tablet and show a low interfacial tension towards aqueous fluids. Rapid penetration by water throughout the entire tablet matrix to facilitate its breakup is thus achieved. Concentrations of disintegrant that ensure a continuous matrix of disintegrant are desirable and levels of between 5 and 20% are common. 

Damage of concrete in aggressive media is accelerated by ice formation. There are several factors affecting the destraction of concrete as a result of capillary water freezing. Water does not freeze in the gel pores, because they are too small for stable ice nuclei formation. The monomolecular layer of adsorbed water, bound with the surface forces, does not freeze too. The temperature of water freezing in capillaries varies with capillary diameter, it is assumed as equal of about -15 °C. The permeability of concrete is an important factor, because water is penetrating into it as a result of capillary action. The process occurs significantly more rapidly when concrete is under the unilateral hydrostatic water pressure. 

An important factor of governing oil recovery is the wettability of porous rock, which affect the existence form of residual oil. The size of wettability is indicated by contact angle (Lohne, 2010). Rock is hydrophilic when 9 < 90°, the smaller the 0 is, the more hydrophilic the rock will be The rock is hydrophobic when 6 > 90°, the larger the 0 is, the more hydrophobic the rock will be The rock is neutral wetted when 0 = 90°. Reservoir rocks are composed of numerous capillary, it will create capillary force in oil-water interface when water-flooding driving oil, which is correlated with the contact angle between formation fluid and porous rock is given by Laplace equation ... 

Thermal management of PEMFC is key to ensure high cell performance and efficiency. The irreversibility of electrochemical reactions and joule heating are the most important factors causing heat generation inside PEM fuel cells. The temperature distribution in the cell has a strong impact on the cell performance. It influenees the water distribution by means of condensation and affects the multi-component gas diffusion transport characteristics through thermo capillary forces and thermal buoyancy. 

Because strength affects endurance, all of the factors discussed previously as influencing strength, also influence endurance. In addition to muscle physiology and muscle strength, endurance is dependent upon the extensiveness of the muscle s capillary beds, the involved neuromuscular mechanisms, contraction force, load, and the rate at which the activity is performed. 

The microscopic displacement efficiency is affected by the following factors interfadal and surface tension forces, wetlabihty, capillary pressure, and relative permeability. 

Recovery factors from oil reservoirs with use of surfactants and water injection with surfactants can be affected strongly by the rate and level of spontaneous imbibition. Improved oil recovery from low permeability rock may consequently be possible by decreasing the capillary to gravity force ratio, i.e. decrease Mb and Q. This could be done by decreasing IFT between oil and water if the displacement rate does not end up too slow for commercial use. In the following sections, displacement of oU by spontaneous imbibition at high and low IFT are considered for each wettability state water-wet, mixed-wet and oil-wet. 

In general, the smaller the scale factor (i.e., closest to prototype), the better as it minimizes the scale effects due to dominant forces not being in proper proportion. A typical scale factor is Lr = Prototype length/model length = 100, or 100 m in the prototype is equivalent to 1 m in the model. Of course, a value smaller than this, like 50 or 25 is even better, but the model costs are usually much higher and difficult to justify except for sediment transport studies. Larger scales can be used, but other concerns due to measurement error and capillary effects can adversely affect the model. Laboratory effects are a concern due to artificial boundaries in a physical model like walls. 

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