A vapor leak enters ventilation air at 2.0 kg/h while clean air flow is 1,000 kg/h. Assuming dilute mixing, vapor mass fraction is most nearly:
- (A)0.0002
- (B)0.002
- (C)0.02
- (D)0.5
Show worked solution
Answer: (B)
Mixed mass fraction is 2/(1,002)=0.001996, about 0.20 wt%.
A dilute steady enclosure balance places leak mass in total exhaust flow.
Total mixed flow is 1,002 kg/h.
FE Reference Handbook — Safety: Ventilation and Dispersion
Why the other choices appear
- (A)Using 10,000 kg/h instead of 1,000 kg/h understates concentration.
- (C)Using 100 kg/h ventilation overstates concentration tenfold.
- (D)Assuming equal leak and air flows ignores the stated dilution.