Question

4. A group of researchers is testing a kerosene heater for NO emissions. The experiments are performed in a well-mixed 27m3 room with an air exchange rate of 0.39 ach. After one hour of the heater being on the NO concentration was 4.7 ppm (1 atm and 25°C). Assume NO can be treated as a conservative pollutant.

a) What is the NO source strength of the heater (mg/hr)?

b) The heater runs for one hour and then is turned off (no emissions). What would the NO concentration be one hour after the heater is turned off (mg/m3 )?

Answer 1

Ans) Given,

Volume of room (V) = 27 m³

Air exchange rate ( I ) = 0.39 ach

Concentration of NO (C) = 4.7 ppm

a) Convert concentration of NO to mg/m³

C (mg/m³) = ppm x Molecular weight / 24.4625

= 4.7 x 30 / 24.4625

= 5.76 mg/m³

Source strength = I x V x C / (1 - e^-It )

where, t = time in hour

= 0.39 x 27 x 5.76 / ( 1 - e^{-0.39 x 1})

= 187.6 mg/hr

or 188 mg/hr

b) After 1 hr of turning of heater,NO concentration C,

C = C_o e^-It

   where C_o = Initial concentration

C = 5.76 x e ^{-0.39 x 1}

C = 5.76 x 0.677

C = 3.90 mg/m³