GATE 2026 ES – Question 60
At height 30 m, a stack cross-section is divided into four equal sectors. Sector velocities are 15,17,19,21 m/s and corresponding $SO_2$ concentrations are 1000,1150,1250,1275 mg/m³. Find the mean emitted concentration in mg/m³,to two decimals.
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Correct answer: 1180 to 1183
Explanation
The concentration of the combined emitted flow is total pollutant mass flux divided by total volume flux. Equal areas cancel, giving $$\bar C=\frac{\sum v_iC_i}{\sum v_i}=\frac{15(1000)+17(1150)+19(1250)+21(1275)}{15+17+19+21}=1181.59722\ldots.$$ Answer **1181.60 mg/m³**. An unweighted concentration mean would disregard different sector flow rates.