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A fan running at a speed of 280 rpm circulates 105 m3/s of air in a mine. If the power input to the motor for driving the fan is recorded to be 75 kW, with the combined efficiency of fan and motor at 70%. If the fan pressure is to be increased by 200 Pa by changing the fan speed. the fan speed in rpm will become
A mine ventilation system consists of two splits A and B with resistances of 0.8 Ns2m-8 and 3.2 Ns2m-8, respectively as shown in figure. Trunk airways have resistance of 0.2 Ns2m-8. The main mine fan is generating pressure of 500 Pa.
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The flows in the two splits are equalized by placing a booster fan in split B. Assume that the fan pressure does not change after installation of the booster fan. The size of the booster fan in Pa is
The fan drift pressure readings and fan quantities are measured to be 500 Pa and 65 m3/s respectively at the time when NVP aids fan pressure. On reversal, the fan delivers a quantity of 50 m3/s while acting against NVP with fan drift pressure of 600 Pa. Assuming that the NVP remains constant in both cases the total resistance of the mine in Ns2/m8 will be
A fan running at a speed of 280 rpm circulates 105 m3/s of air in a mine. If the power input to the motor for driving the fan is recorded to be 75 kW, with the combined efficiency of fan and motor at 70%. the fan pressure in Pa is
একটি পানিপূর্ণ কুয়ার গভীরতা 20m ও ব্যাস 2 m. কুয়াটিকে পানি শূণ্য করার জন্য 5 HP এর একটি পাম্প লাগানো হল। অর্ধেক পানি তোলার পর পাম্পটি নষ্ট হয়ে গেল। বাকি পানি তোলার জন্য একই ক্ষমতা সম্পন্ন আর একটি পাম্প লাগানো হল। প্রথম পাম্প দ্বারা সম্পাদিত কাজের পরিমান নির্ণয় কর।(The depth and diameter of a water filled well are 20 m and 2 m respectively. An engine of 5 HP is attached to pump out the water. The pump was ruined after emptying half of the water. Then another pump of same capacity was attached to pump out rest of the water. Determine the work done by first pump.) 
Large, medium and small ships are used to bring water. 4 large ships carry as much water as 7 small ships, 3 medium ships carry the same amount of water as 2 large ships and 1 small ship. 15 large, 7 medium and 14 small ships, each made 36 journeys and brought a certain quantity of water. In how many journeys would 12 large, 14 medium and 21 small ships bring the same quantity ?
City High School must put together a debating team consisting of four debaters.There are candidates of equal ability : X,Y and Z who are all seniors; and A,B,C and D who are all juniors..The school requires that there should be two seniors and two juniors in the team.It is also necessary that all of the debaters be able to work with one another. *Debaters Y and A cannot work together. *Debaters Z and C cannot work together. *Debaters A and B cannot work together. which of the following statements must be false? 1.Debaters Y and C are never selected together. 2.Debaters Z and D are never selected together. 3.Debaters Z and D are never selected together.
The resistances of two splits A and Bare 0.35 Ns2m-8 and 0.05 Ns2m-8 respectively. The combined resistance of the shafts and trunk airways is 0.4 Ns2m-8. A booster fan is planned to be installed in split A to increase the quantity flowing through it. Assuming that the surface fan continues to operate at a constant pressure of 1000 Pa, the critical pressure of the booster fan in Pa is
A mine fan produces 30 m3/s of air at 240 Pa pressure running at 1400 rpm. If the fan speed is increased to 2100 rpm, the pressure in Pa and the quantity in m3/s generated by the fan will be
Pressure characteristic of a mine fan is given by. P = -0.06Q2 + 400. where P is the pressure in Pa and Q is the quantity in m3/s. The resistance of the mine is 0.19 Ns2/m8. An identical fan is installed in the mine to operate in series with the existing fan. The new mine quantity in m3/s is