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:
“When I from black and he from white cloud free,
And round the tent of Godlike lambs we joy,
I’ll shade him from the heat till he can bear
To lean in joy upon our father’s knee;
And then I’ll stand and stroke his silver hair,
And be like him, and he will then love me.”
—William Blake (1757–1827)
“All Coolidge had to do in 1924 was to keep his mean trap shut, to be elected. All Harding had to do in 1920 was repeat “Avoid foreign entanglements.” All Hoover had to do in 1928 was to endorse Coolidge. All Roosevelt had to do in 1932 was to point to Hoover.”
—Robert E. Sherwood (1896–1955)