Institute for Radiohydrometry of the Technical University Munich

Layout of a flow model for the imitation of installed screens under operational conditions

TU München 1

∆ top

Permeabilities and Hydraulic Properties

You will find the advantage of con-slot Screens in the large open area. However, since the free open area alone is not the criteria for the efficiency, a direct comparison of con-slot Screen open area with the open area of other screen media should never be made!

We note that in practical application very of­ten the width of the support structure “b2” is being omitted when investigating the open area of a profile wire screen structure. First it falsifies the open area and then it alters the results of the flow pattern calculation. The values of the specific properties of a con-slot Screen structure are to be found in the constants “a” and “b” - see the Forchheimer-Schnebelli law - (see formula)

TU München 2

This means: even if the direct comparison between con-slot and other screen structu­res does look disadvantageous for con-slot the calculation of the flow-losses alone proves the advantages of the con-slot Screen! High flow rates with negligible pressure los­ses - the advantage of the V-form giving slot, comparable with a Venturi-nozzle!

TU München 3

Hydraulic properties of filter tubes or filter plates are related to physical laws which de­fine the flow gradient (pressure loss) through the screen wall structure as a function of the velocity of flowing media. Experiments have shown that with the increasing flow velocity (filter velocity) “v” also the gradient “l” at the screen wall structure increases.

TU München 4

The diffe­rence between laminar and turbulent flow as known in fluid dynamics is also valid for filtra­tion. However, the following difference must be noted: The transition between laminar and turbulent flow through con-slot Screen structures does not occur abruptly as deter­mined likewise for pipes and channels, but gradually. It is comparable to the behaviour of porous medias i.e. precoat filter medias, filtersand, filter of sintered metal, etc., or ion-exchange medias like resin, catalyst beds, etc. Experience has shown that the combination of both, con-slot Screens and above medi­as, develop advantageous flow characteri­stics for operation and efficiency.

Therefore, no mathematical equation can be formulated which only describes the resist­ance of a screen structure either for laminar or for turbulent flow. The best approach is to distinguish between “viscous” and “inert” flow of the media through the screen wall structure.

TU München 5

Constants “a” and “b” are resistivity figures of the con-slot screen structure and are related to the viscous and inert flow characteristics.

Research conducted at the Institute for Radiohydrometrie at Munich, showed that the con-slot Screen structure permeability (flow capacity) can be defined by a “k”-factor:

TU München 6

Consequently:
The larger the k-factor (and not the open area!), the larger is the filtration/flow effi­ciency.
Efficiency diagrams for standard screen structure are available for you, calculated for water with a temperature of 14 degrees Cel­sius. We are at your disposal with our programmes, if the determination of flow pattern for other conditions/for other media is re­quested.

con-slot Screens: High permeability combined with high mechanical strength.

TU München 7

TU München 8
TU München 9

∆ top


con-slot SCREENS | Industriegebiet Hafen | Graue Riethe 2 | D-29378 Wittingen
Tel: +49 5831 2515-0 | Mail: info@con-slot.de