lindab | we simplify construction Supply air nozzle Resulting sound effect level To calculate the resulting sound effect level from the noz- zles, add the sound effect level from the nozzles (L WA nozzle) and the sound effect level from the flow noise in the duct (L WA duct) logarithmically. Diagram 1, sound effect duct, L WA duct. , 7! D"! , 7! D"! Q 6 ;LS= Q 6 ;M H= Diagram 2, addition of sound levels. Difference to be added to the highest dB value (dB). 3 Calculation Extension of throw for two nozzles, positioned side by side: If two nozzles are positioned next to each other, the air jets will be amplified, thereby extending the throw. To calculate this, use the diagram below, in which the distance between the nozzles is designated D. The calculation factor K 4 must be multiplied by the throw l 0.3 . The throw is not extended fur- ther with more nozzles. + + $;M= L ;M= 2 1 0 0 2 4 6 8 Difference between the dB values (dB) 10 12 L W Duct v Duct L W Nozzle v Nozzle Sample calculation: LAD-200 Δ P t nozzle q = 100 l/s 90 Pa Duct size: In order to achieve a sensible distribution of the air out to the nozzles without using a damper, it is recommended that the pressure loss in the nozzle be 3 times higher than the dynamic pressure in the duct system. Selected duct dimension: Ø 400 Number of nozzles at joint: 6 Volume of air in the duct: 6x100 = 600 l/s L WA duct (can be seen in diagram 1): L WA nozzle (can be seen in product diagram): Difference between db values: 43 dB(A) 37 dB(A) 6 dB(A) Value to be added to the highest dB value (diagram 2): 1 dB(A) Resulting sound effect level: 43 +1 = 44 dB(A) Sample calculation: LAD-125. Distance D = 1.5 metres. Volume of air: q = 15 l/s Diagram throw under selected nozzle Specified throw: D [m] / l 0.3 [m]: l 0.3 = 7 m 1.5 / 7 = 0.21 K 4 calculation factor Can be seen in the diagram: K 4 = 1.25 Resulting throw K 4 x l 0.3 = 1.25 x 7 m = 8.75 m Lindab reserves the right to make changes without prior notice 3 2021-02-09
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