Surface Environment, Mine Ventilation and Underground Hazards · Mine Ventilation · 2 marks · Multiple choice
Four identical districts have total flow 3500 m³/min at stated fan-drift pressure 1.15 kPa. Sealing one raises resultant resistance by 0.072 N s²/m⁸. With the fan stopped and that district still sealed, the flow is 850 m³/min. Find NVP in Pa.
The source treats the initial stated pressure as the system pressure loss. Then R=1150/(3500/60)². After sealing, R′=R+0.072. With only natural pressure driving flow, NVP=R′(850/60)²=82.28 Pa, B. If the initial fan pressure were interpreted as excluding an already active NVP, a different coupled balance would result; the keyed pressure convention is stated explicitly.
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