Various efficiencies of a centrifugal pump are related as (where, ηm = mechanical efficiency ηv = volumetric efficiency. ηma = manometric efficiency ηo = overall efficiency)

A

ηma x ηm x ηv = ηo

B

ηm = ηv . ηma

C

ηma = ηm x ηv

D

ηv = ηm x ηma

Power required (in watts) to drive a centrifugal pump is (where H_m = Manometric head in metres, w = Specific weight in N/m³, Q = Discharge of the pump in m³/s and $${\eta _{\text{o}}}$$ = Overall efficiency of the pump)

A

$$\frac{{{\text{w}}{{\text{H}}_{\text{m}}}}}{{{\text{Q}} \times {\eta _{\text{o}}}}}$$

B

$$\frac{{{\text{wQ}}{{\text{H}}_{\text{m}}}}}{{{\eta _{\text{o}}}}}$$

C

$$\frac{{{\text{wQ}}}}{{{{\text{H}}_{\text{m}}} \times {\eta _{\text{o}}}}}$$

D

$$\frac{{{\text{wQ}} \times {\eta _{\text{o}}}}}{{{{\text{H}}_{\text{m}}}}}$$

The hydraulic efficiency of a Francis turbine is 90%, the mechanical efficiency is 95% and the volumetric efficiency is assumed to be 100%. Fine the overall efficiency (in %)?

A

80

B

85.5

C

87.5

D

83.3

The hydraulic efficiency of a Kaplan turbine is 95%, the mechanical efficiency is 93% and the volumetric efficiency is assumed to be 100%. Fine the overall efficiency (in %)?

A

80.05

B

93.15

C

87.55

D

88.35

A centrifugal pump designed to pump water is employed to pump a more viscous oil. In the later case, the pump

A

Develops a lower head

B

Capacity is reduced

C

Requires more power

D

All of the above

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.)

A

2.54 × 104 J

B

1.44 × 104 J

C

2.34×104 J

D

1.54 × 104 J

E

1.54 ×104 J

A, B and C are three small pumps fitted to a tank. D is a large pump fitted to the tank. Pump B is 25% more efficient than A. Pump C is 20% more efficient than B. Pump D is 4/3rd efficient of pump C. All of the pumps are used to fill the tank. What is the ratio of the time taken by pumps A and B to fill the tank together to the time taken by the pumps B and D to fill the tank together?

A

17 : 8

B

15 : 5

C

12 : 8

D

13 : 9

E

32 : 9

A U-tube manometer containing a liquid of specific gravity S measures gauge pressure of water flowing in a pipe. h2 = difference in level of manometric liquid in the two limbs h1 = height of water between point of connection of pressure tap and level of manometric liquid in the limb to which it is connected by a tube bending down. The measured gauge pressure is:

A

h₂ m of manometric liquid

B

h₂.S m water

C

(h₂.S – h₁) m of water

D

h₁ m water

Manometric head, in case of a centrifugal pump, is equal to

A

Suction lift + Loss of head in suction pipe due to friction + Delivery lift + Loss of head in delivery pipe due to friction + Velocity head in the delivery pipe

B

Work-done per kN of water Losses within the impeller

C

Energy per kN at outlet of impeller Energy per kN at inlet of impeller

D

All of the above

Manometric head, in case of a centrifugal pump, is equal to __________

A

Suction lift + Loss of head in suction pipe due to friction + Delivery lift + Loss of head in delivery pipe due to friction + Velocity head in the delivery pipe

B

Energy per kN at outlet of impeller – Energy per kN at inlet of impeller

C

Workdone per kN of water – Losses within the impeller

D

All of the mentioned

Various efficiencies of a centrifugal pump are related as (where, η_m = mechanical efficiency η_v = volumetric efficiency. η_ma = manometric efficiency η_o = overall efficiency)

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