1. The diameters of an impeller of a certrifugal pump at inlet and outlet are 20cm & 40cm respectively. Determine the minimum speed for starting the pump if it works against a head of 25m.
Answer: 1221.2 rpm
2. Find the power required to drive a centrifugal pump which delivers 0.02m3/s of water to a height of 30m through a 10cm diameter pipe and 90m long. The overall efficiency of the pump is 70% and f= 0.009 in the formula
Answer: 11.5 kw
3. The diameter of an impeller of a centrifugal pump at inlet and outlet are 300 mm and 600mm respectively. The velocity of flow at outlet is 2.5m/s and vanes are set back at an angle of 45° at outlet. Determine the minimum starting speed of the pump if the manometric efficiency is 75%.
Answer: 159.31 rpm
4. The diameter of a centrifugal pump which is discharging 0.035m3/s of water against a total head of 25m is 0.05m. The pump is running at 1200rpm. Find the head, discharge and ratio of powers a geometrically similar pump of diameter 0.3m when it is running at 2000 rpm.
Answer: 25m, 0.0126 m3/s 2.777
5. The internal and external diameters of the impeller of a centrifugal pump are 300mm & 600mm respectively. The pump is running at 1000rpm. The vane angles at inlet and outlet are 20° and 30° respectively. The water enters the impeller radially and velocity of flow is constant. Determine the work done by the impeller per unit weight of water.
Answer: 68.89 Nm/N
6. A centrifugal pump is running at 1000rpm. The outlet vane angle of the impeller is 30° and velocity of flow at outlet is 3m/s. The pump is working against a total head of 30m and the discharge through the pump is 0.3m3/s. If the manometric efficiency of the pump is 75%. Determine (i) diameter of the impeller (ii) The width of the impeller at outlet.
Answer: (i) 43.1 cm (ii) 7.4 cm
7. Find the rise in pressure in the impeller of a centrifugal pump through which water is flowing the rate of 15 lit/sec. The internal and external diameters of the impeller are 20cm & 40cm respectively. The widths of impeller at inlet and outlet are 1.6 cm and 0.8cm. The pump is running at 1200rpm. The water enters the impeller radially at inlet and impeller vane angle at outlet is 30°. Neglect losses through the impeller.
Answer: 31.8 mm
8. A single acting reciprocating pump running at 30rpm, delivers 0.012m3/s of waters. The diameter of the piston is 25cm & stroke length 50cm. Determine (i) the theoretical discharge of the pump, (ii) co-efficient of discharge, (iii) Slip and % of the slip in the pump.
Answer:
(i) 0.01227m3/s
(ii) 0.978
(iii) 0.00027 m3/s
(iv) 2.20%
9. A single-acting reciprocating pump has a cylinder of diameter 150mm & of stroke length 300mm. The centre of the pump is 4m above the water surface in the sump. The atmospheric pressure head is 10.3 m of water and pump is running at 40 rpm. If the length and diameter of the suction pipe are 5m & 10cm respectively, determine the pressure head due to acceleration in the cylinder
(i) At the beginning of the suction stroke
(ii) In the middle of the suction stroke.
Answer: (i) 3.018 m (ii) 0
10. A double-acting reciprocating pump, running at 50rpm is discharging 900litres of water per minute. The pump has stroke of piston is 250mm. The delivery & suction heads are 25m &4m respectively. Find the slip of the pump and power required to drive the pump.
Answer: 0.0027 m3/s, 9.3 Kw
11. A single acting reciprocating pump has piston diameter 15cm and stroke length 30cm. The centre of the pump is 5m above the water level in the sump. The diameter and length of the suction pipe are 10cm and 8m respectively. The separation occurs if the absolute pressure head in the cylinder during suction stroke falls below 2.5m of water. Calculate the maximum speed at which the pump can run without separation. Take atmospheric pressure head = 10.3m of water.
Answer: 30.45 rpm
12. A single acting reciprocating pump has a plunger of 100mm diameter and a stroke length 200mm. The centre of the pump is 3m above the water level in the sump and 20m below the water level in a tank. To which water is delivered by the pump. The diameter & length of the suction pipe are 50mm & 5m while of the delivery pipe are 40mm & 30m respectively. Determine the maximum speed at which the pump may be run without separation. If separation occurs at 7.3575N/cm2 below the atmospheric pressure. Take atmospheric pressure head= 10.3 of water.
Answer: 36.22 rpm
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