Flash Evaporation
Flash (or partial) evaporation is the partial vapor that occurs when a saturated liquid stream undergoes a reduction in pressure by passing through a throttling valve or other throttling device. This process is one of the simplest unit operations. If the throttling valve or device is located at the entry into a pressure vessel so that the flash evaporation occurs within the vessel, then the vessel is often referred to as a flash drum.
If the saturated liquid is a single-component liquid (for example, liquid propane or liquid ammonia), a part of the liquid immediately "flashes" into vapor. Both the vapor and the residual liquid are cooled to the saturation temperature of the liquid at the reduced pressure. This is often referred to as "auto-refrigeration" and is the basis of most conventional vapor compression refrigeration systems.
If the saturated liquid is a multi-component liquid (for example, a mixture of propane, isobutane and normal butane), the flashed vapor is richer in the more volatile components than is the remaining liquid.
Uncontrolled flash evaporation can result in a boiling liquid expanding vapor explosion (BLEVE).
Read more about Flash Evaporation: Flash Evaporation of A Single-component Liquid, Equilibrium Flash of A Multi-component Liquid, Contrast With Spray Drying
Famous quotes containing the word flash:
“Tom: All right, boys. C’mon. Why don’t you say I’m a yellow belly and a big mouth at that?
Shep: You yellow? Who thinks you’re yellow? Did you hear what he said? A guy who’s got the nerve to marry? That’s more than Flash Gordon ever did.”
—Billy Wilder (b. 1906)