Level swell characterisation

As described in Annex 3, the amount of level swell increases with gas or vapour superficial velocity. At bench-scale, the superficial velocity due to runaway will be very low compared with that at plant-scale, so that very little level swell occurs in bench scale tests, even for Inherently foamy fluids. However, some level swell at bench-scale is required to determine whether the reacting system is inherently foamy or not. For tempered systems, this can be achieved by rapid depressurisation of the test cell to give flashing and a consequent high superficial velocity, and this is one of the ways in which the DIERS bench-scale apparatus can be used. (Note that 

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Level swell is characterised by the. void fraction within the swelled liquid, a. This is correlated for each flow regime as a function of 4V the dimensionless ratio of the superficial gas/ vapour velocity to the bubble rise velocity, i.e ... 

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