Problem
Chimney height is 40 m. Air density 1.20 kg/m³ and flue-gas density 0.85 kg/m³.
Formula
ΔP=gH(ρa−ρg)
Solution
=9.81×40×(1.20−0.85)=137.34 Pa; divide by 9.80665.
Answer
14.0 mm water
Engineering check
Verify units, magnitude, assumptions and physical meaning before accepting the result.