Multiwir Packings
Multiwir Packings
The name MULTIWIR (wir [vi:r] is Polish word for vortex) is derived from a phenomenon of multiple vortices induced in the gas stream flowing through a specifically organized packing. The packing consists of layers of parallel slats arranged such that the slats of adjacent layers cross at a certain angle. This construction causes the flowing gas to divide into multiple rotating jet streams.
Two main forms of Multiwir structured packings have been applied so far in the industry: the rectangular and the annular. The rectangular packing consists of layers of parallel straight slats. The annular form is built from curved slats and permits radial gas flow.
The stream of inlet gas entering the packing divides into multiple jet streams flowing along the passages between the slats. The jet streams flowing between slats of adjacent layers of the packing come into contact with each other at a certain angle and, as a result of momentum transfer, a forced rotational flow takes place. The angular velocity of the rotation has been experimentally proved to be constant. The frequency of revolutions depends on gas velocity. In practical applications, the radius of the vortices equals 15 ÷ 30 mm and its frequency is contained within the range 30 ÷ 60 s-1.
The centrifugal force resulting from the rotational flow of gas streams is the main factor responsible for separating droplets and solid particles from gases. The separation efficiency depends on precise packing construction parameters and on gas velocity. The highest grade of separation observed experimentally reached 90 ÷ 100% within the range of particle diameter grater than 2 µm.
The inventor of Multiwir packings Jan Kwaśniak, PhD Eng., conducted experimental research on the gas flow characteristics and the separation efficiency at Technical University in Lodz (Politechnika Łódzka), Poland and at Technical University in Clausthal, Germany in 1970s and 1980s. His research was further continued by German scientists at universities in Karlsruhe, Stuttgart and Essen.