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Rectangular Silencers
Selecting a rectangular silencer.
Rectangular silencer design is all about gaps between splitters (the air path) and the maximum velocity through the gap. The smaller the gap the better the attenuation. As a gap gets smaller the air velocity through the gap will increase unless we add more gaps for the air to get through. The reason we need more splitters is so that we can bet more gaps of a certain width. We also get better attenuation if we increase the length of the silencer and the thickness of the splitters. Different styles also have an effect on the attenuation provided.
There is also a pressure loss from shock and friction losses which should also be considered. If this becomes substantial then it may be necessary to reselect the fan with a pressure allowance for the silencer.
Note that you have the option to fix the 'A' dimension and the 'B' dimension of the silencer. The B dimension is equivalent to the fan casing or inlet box width and is the recommended orientation with Long Splitters selected.
Selecting Short Splitters orientation on a fan outlet can lead to starvation of some splitter gaps due to the uneven outlet flow.
Centrix will fix the 'A' dimension by default and it is recommended that you leave the Fix 'B' dimension unchecked except in special circumstances. Leaving the 'B' dimension free to enlarge as required will usually generate the most economical solution.
Centrix automatically sets the minimum A and B dimensions to match the casing outlet or inlet size and sets an appropriate maximum gap velocity.
You can set default silencer styles and thicknesses by leaving checked the ones you want to use and then clicking the 'Set Defaults' button. Style 4 should only be used for very low outlet velocities (< 12 m/s) as it has a high loss associated with it. The more styles and thicknesses you leave checked the more likely you are to obtain the most economical solution but the longer the selection process will take.
Click the 'Calculate' button under the 'Auto Design' heading to start the automatic selection process and fill the grid with selections. Results are automatically sorted by lowest cost although any expansion costs are not included in this list.
Double click a row or select a cell and click the 'Detail' button to show the Detail form.
The Save to Centrix button must be clicked in the Detail form to save the design and costing information to Centrix.