ISSN:
0001-1541
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Phenomenologically based model for forth height was developed using the assumption of both vapor-and liquid-continuous zones within the total froth height. The model demonstrates the importance of liquid and vapor rates and determines that the Weber number (and therefore droplet size and surface tension) has little effect on froth height.A composite air/water database including entrainment data for both the spray and froth regimes is used to develop an entrainment correlation as a function of the ratio of tray spacing to froth height (Ts/h2φ) and the average froth density (φ2φ = hL).For conditions resulting in the ratio of liquid inventory to the perforation diameter (hL/dH) 〈4, the height, equation requires an empirical correction for froth height, and entrainment depends onφ2φ.This results from the predominantly vapor-continus nature of the froth. For large values of hL/dH, the theoretical value for h2φ appears adequate and entrainment is essentially independent of φ2φ, since most of the liquid is contained in the liquid-continuous region located far away from the underside of the tray above. In such cases, entrainment is from a light spray on top of the liquid-continuous region, and therefore entrainment depends much less on φ2φ.The differen dependency of entertainment on φ2φ can be used as a method to identify the spray-froth transition. For hL/dH〈2, a spraylikecondition exists; for hL/dH 〉 2, a frothlikecondition exists.The reported dependency of air/water system entrainment on major geometry and operating conditions is described well by the new correlation. Alternate correlations for the non-air/water entrainment data, however, are required. New methods for estimating the impact of entrainment on efficiency are given.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/aic.690410907
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