The stack pressure is created by 10 m height of stack and 15°C temperature difference. Themotive force due to the stack pressure over a cross section

Q. The stack pressure is created by 10 m height of stack and 15°C temperature difference. Themotive force due to the stack pressure over a cross section area of 2.5 m² is________N.

1. 15.75
2. 5.75
3. 75.75
4. 15

Ans: 15.75

Solution:

Stack effect or chimney effect is the movement of air into and out of buildings, chimneys, fluegas stacks, etc, resulting due to a difference in indoor-to-out door air density, resulting from temperature and moisture differences. The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect.

Stack pressure in N/sq m, P = 0.042 × h × ∆T

Stack pressure = 0.042 × 10 × 15 = 6.3 N/sq m

Stack pressure over given cross-sectional area = 6.3 × 2.5 = 15.75 N