Liquids pool evaporation or boiling

A more complex model for pool spread has been developed by Webber (1991). This model is presented as a set of two coupled diiSerential equations which models liquid spread on a flat horizontal and solid surface. The model includes gravity spread terms and flow resistance terms for both laminar and turbulent flow. Solution of this model shows that the pool diameter radius is proportional to t in the limit where gravity balances inertia, and as in the limit where gravity and laminar resistance balance. This model assumes isothermal behavior and docs not include evaporation or boiling effects. 

SO3 or oleums are usually stored and transported in their liquid form. Therefore, almost all of the accidents that have occurred involved the generation of a liquid pool (with the exception of the Richmond accident [Basket et al., 1994]). Although there are numerous pool evolution models in the literature, most of them deal with nonreactive liquids, with boiling points either much lower or much higher than typical ambient temperatures. The regime of behavior is then clearly either that of a boiling pool or the evaporation of a liquid of low volatility. 

When we look around, we see that matter takes the physical form of a solid, a liquid, or a gas. Water is a familiar example that we routinely observe in all three states. In the solid state, water can be an ice cube or a snowflake. It is a liquid when it comes out of a faucet or fills a pool. Water forms a gas, or vapor, when it evaporates from wet clothes or boils in a pan. In these examples, water changes state by losing or gaining energy. For example, energy is added to melt ice cubes and to boil water in a teakettle. Conversely, energy is removed to freeze liquid water in an ice-cube tray and to condense water vapor to liquid droplets. 

Material stored at or below its atmospheric pressure boiling point has no superheat. Therefore there will be no initial flash of liquid to vapor in case of a leak. Vaporization will be controlled by the evaporation rate from the pool formed by the leak. This rate can be minimized by the design of the containment dike, for example, by minimizing the surface area of the liquid spilled into the dike area, or by using insulating concrete dike sides and floors. Because the spilled material is cold, vaporization from the pool will be further reduced. 

The use of structured surfaces to enhance thin-film evaporation has also been considered recently. Here, in contrast to the flooded-pool experiments noted above, the liquid to be vaporized is sprayed or dripped onto heated horizontal tubes to form a thin film. If the available temperature difference is modest, structured surfaces can be used to promote boiling in the film, thus improving the overall heat transfer coefficient. Chyu et al. [43] found that sintered surfaces yielded nucleate boiling curves similar to those obtained in pool boiling. T-shaped fins did not exhibit low AT boiling however, a threefold convective enhancement was obtained as a result of the increased surface area. 

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