Pleated Filters

Dimensioning of Pleated Filters

Plissierter Filter
© Photo ITWM

A pleated filter contains a folded filter medium

Quantities of Pleated Filters

A pleated filter contains a folded filter medium to maximize the effective filter surface. The performance of a pleated filter is characterized by the three quantities:  

  • Pressure drop: equals the energy needed to operate the filter.
  • Filter efficiency: the probability that a particle of a given size is filtered.
  • Lifetime: the period of time after which the filter has to be replaced.  

Relation between the Permeability, the Structure and the Quantities

The goal of the project is to establish a relation between the permeability of the filter medium, the channel structure of the pleated filter and the three quantities pressure drop, filter efficiency and filter lifetime. Therefore, we firstly generate a three-dimensional computer model of a particular pleat. In the second step, a flow simulation yields the initial pressure drop of the clean pleat.

Now, particles are put into the flow field. They move through the medium subject to friction forces, inertia and Brownian motion. Their motion is stopped in case of a collision and they deposit due to adhesive forces. Based on the ratio of deposited and not filtered particles, filter efficiencies are computed.

 

Druck und Geschwindigkeit
© Photo ITWM

Pressure and speed

Simulation Example

The above figures show the pressure and the velocity distribution along a pleat. The permeability of the medium on the left hand side is set constant. On the right hand side, the permeability is set lower in the bending motivated by compression effects. The simulations show that the pressure drop is higher in case of the variable permeability

Moreover, the flow velocity is much higher at the inlet of the pleat, since the lower permeability prohibits to some extend flow through the bending. The diagrams on the left illustrate the deposition pattern of 20000 particles at the aforementioned pleats. You can clearly observe lower deposition rates at the bending zone in the second diagram which is again a result of the lower permeability and higher flow rates.

Abscheidepositionen
© Photo ITWM

Deposition position

 

PleatGeo and PleatDict

In the future, these simulations are extended to predict the time-dependent filter efficiency and filter lifetime. These simulations will be made available as new modules PleatGeo and PleatDict of the GeoDict software suite.

 

GeoDict
© Photo ITWM

GeoDict