Boiling liquids pressure effect

Introduction of a vortex or swirl flow, which effectively reduces the pressure at the center and thus reduces the superheat of the boiling liquid metal near the wall. 

BLEVE (Boiling Liquid Expanding Vapor Explosion) See Boilover the same phenomenon may occur in a pressurized container, resulting in an explosion or bursting of the tank or vessel in which a fire is occurring. The term is almost exclusively used to describe a disastrous effect from a crude oil fire. 

Impurities can be present in the boiling liquid itself. The evidence is strong that traces of dissolved material (excluding surface-active agents of course) have but a small effect on boiling, whereas suspended material is much more important. Wismer s important experiments on superheated liquids show a distinct difference between the maximum superheat attainable with water at atmospheric pressure in the presence of dissolved material and the values resulting for suspended matter. Some of the results are given in Table VI. 

A boiling liquid-expanding vapor explosion occurs when a pressure vessel containing a liquid is heated to a temperature liigh enough to cause tlie metal to lose strength and rupture. The source of tlie heat is normally another fire near tlie vessel. The effects of a BLEVE depend on whether tlie liquid in die vessel is flanunable. If the liquid is flammable, it may eitlier cause a fire, which radiates heat, or fonii a vapor cloud, which could result in a second explosion. 

As was shown previously, the addition of an impurity to a liquid decreases its vapor pressure according to Raoult s law. This change in vapor pressure will affect the melting point of the compound as well as the boiling point. The effect of temperature on the vapor pressure of a solid is given by... 

From API Std. 526 we would select an H orifice relief valve with effective orifice area 0.785 in. A size 2H3 carbon steel relief valve will allow a set pressure up to 740 psig in the expected range of operation temperature. In practice, however, we would have to consider two-phase flow due to entrainment of boiling liquid with the vapor and might select a larger orifice size after more detailed design. 

A boiling-liquid expanding-vapor explosion (BLEVE) can occur if a container of liquid or liquified gas at temperatures above their atmospheric-pressure boiling points were to rupture. Sudden loss of containment and reduction in pressure can result in explosive vaporization of some of the liquid, and the sudden increase in volume can propel parts of the container to great distances and create blast effects (pressure and impulse). Eurther, if the superheated liquid or liquified gas is flammable, a fireball involving the ejected vapor, aerosol, and liquid can result, particularly if the cause of the overpressure and rupture is exposure to fire. 

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