11. In a mine between upcast shaft and downcast shaft, two airways are connected in parallel and their resistances are 100 and 120 Ns-2m-8 respectively. The resistance of upcast shaft, downcast shaft and the fan drifts are 10, 20, and 5 Ns-2m-8 respectively. The fan drift air pressure is 15 MN/m2. The rate of airflow through the mine in m3
12. Air at a density of 1.2 kg/m3 flows in a straight duct such that the velocity at the centre is 12.5 m/s. the method factor for the velocity profile is known to be 0.80. The air flow encounters a symmetric expansion such that the cross- sectional are of the duct becomes double. The static pressure value at the inlet and outlet of the expansion are 60 Pa and 90 Pa respectively. Neglecting friction the shock pressure loss on account of expansion in Pa is
13. Geothermic gradient is
14. Mean air temperature of a 450 m deep downcast shaft is 29°C and that of the upcast shaft is 37°C. The height of the motive column in m is
15. Air of 20.8% O2, concentration enters a coal mine panel at 20 m3/s and exits with 20.6% O2. The oxygen depletion is due to oxidation of carbon in spontaneous heating process only, assuming the density of oxygen as 1.3 kg/m3 and the calorific value of carbon as 34 MJ/kg, the heat generated in kW from the panel due to spontaneous oxidation is
16. The main fan operating point of a ventilation system is shown in the figure below. If an NPV of 200 Pa assists the ventilation system, the resultant pressure (Pa) and quantity (m3) generated by the
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