The cloud point of a fluid is the temperature at which dissolved solids are no longer completely soluble, precipitating as a second phase giving the fluid a cloudy appearance. This term is relevant to several applications with different consequences.
In the petroleum industry, cloud point refers to the temperature below which wax in diesel or biowax in biodiesels form a cloudy appearance. The presence of solidified waxes thickens the oil and clogs fuel filters and injectors in engines. The wax also accumulates on cold surfaces (e.g. pipeline or heat exchanger fouling) and forms an emulsion with water. Therefore, cloud point indicates the tendency of the oil to plug filters or small orifices at cold operating temperatures.
In crude or heavy oils, cloud point is synonymous with wax appearance temperature (WAT) and wax precipitation temperature (WPT).
The cloud point of a nonionic surfactant or glycol solution is the temperature where the mixture starts to phase separate and two phases appear, thus becoming cloudy. This behavior is characteristic of non-ionic surfactants containing polyoxyethylene chains, which exhibit reverse solubility versus temperature behavior in water and therefore "cloud out" at some point as the temperature is raised. Glycols demonstrating this behavior are known as "cloud-point glycols" and are used as shale inhibitors (see Talk). The cloud point is affected by salinity, being generally lower in more saline fluids.
Famous quotes containing the words cloud and/or point:
“That which is given to see
At any moment is the residue, shadowed
In gold or emerging into the clear bluish haze
Of uncertainty. We come back to ourselves
Through the rubbish of cloud and tree-spattered pavement.
These days stand like vapor under the trees.”
—John Ashbery (b. 1927)
“There could be no fairer destiny for any physical theory than that it should point the way to a more comprehensive theory in which it lives on as a limiting case.”
—Albert Einstein (1879–1955)