Explosion protection

Old Truth Stands no Longer: How dangerous is splash filling really?

Page: 2/5

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The Electric Waterfall

However, science is no matter of faith but of evidence, for example by experiments. In 2015 these were conducted at the University of Poitiers, France. With a falling height of 5 m, droplets of different liquids at diameters of about 2 mm were tested. Electrostatically charged droplets, accurately defined, were released out of a dispenser fell through cylindrical metal pipes and were collected in a metal cup, all surrounded with an earthed tube.

This measuring principle bases on electric induction and enables to record the extremely low amounts of charges (range of Pico Coulombs of single droplets), being transferred to an electrometer amplifier and indicated on a PC. The measured charge on a single falling droplet is depicted in the diagram on page 44 and in comparison therewith the theoretical course is shown.

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The Amplitude Response

The decisive criterion for evaluation of the droplet charge is its amplitude response, whereby the small changes in view of the extremely small amounts of charge have to be tolerated. It is remarkable to notice, that the peak is getting narrower due to the increasing falling velocity.

It follows: The charge level indicated at the electrometer when the droplet passes the first cylinder is virtually the same when it passes the second, the third, the forth and finally arrives at the collecting cup.

There is a very low charge discrepancy (possibly caused by evaporation of the liquid) which was not detectable even by the extremely sensitive electrometer. In general, no change of the charge was noticed all along the fall on droplets that kept in shape.

Overall Conclusion

It also was determined, that droplets which disassembled themselves in multiple parts during the fall showed a change of their electrostatic loading status. This statement corresponds with the experience of the so called “waterfall electricity”. With a water cascade falling down several hundred meters, electrostatic charges occasionally come into being within the wafts of mist.

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