For example, if 5000 CMH (1.39 m3/s) of air has to be exhausted out, which one of the following is correct by considering, 2.5 m/s as the face velocity?
1) Face area of the louvre with 50% free area is 1.39/2.5 = 0.556 m2 (which means, free area of the louvre is 0.258 m2 and the velocity of exhaust air in this free area is 2.5 * 2 = 5 m/s)
2) Face area of the lourve with 50% free area is 1.39/(2.5*50%/100%) = 1.112 m2 (which means, free area of the louvre is 0.556 m2 and the velocity of exhaust air in the free area is 2.5 m/s.
So, the ASHRAE guideline velocity is the face area velocity or free area velocity?
Thanks in advance.