Mechanical Engineering - Hydraulic Machines - Discussion

Discussion Forum : Hydraulic Machines - Section 1 (Q.No. 1)
1.
Power required to drive a centrifugal pump is directly proportional to __________ of its impeller.
diameter
square of diameter
cube of diameter
fourth power of diameter
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
35 comments Page 3 of 4.

Yogendra maurya said:   1 decade ago
POWER is proportional to Q.H=d^2.V^2=d^2.(pi.dN)^2=which is proportional to d^4.

Mohan said:   1 decade ago
Yes this answer is right but its against affinity laws, also discharge varies to square of this which is also against affinity law.

Afrasiyab said:   1 decade ago
Power is proportional to cube of diameter.

Radhika said:   1 decade ago
Cube of diameter. As per affinity laws option C is correct.

AMAL said:   1 decade ago
@Safy.

I think its d^5.

Because p/(N^3*D^5) = Constant.

Akshat said:   1 decade ago
Answer D is correct, if there is a difference between the velocity triangles and if not then answer C is correct.

JAIMIN said:   1 decade ago
I think D^5 is right answer.

Because from similarity law come the equation of power coefficient P/(N^3 D^5) that's it.

Sreejith said:   10 years ago
Power is proportional to fifth power of diameter.

RAM said:   1 decade ago
Power = density * acceleration due to gravity * discharge * head loss.

Where Q = A * V = area * velocity.

Area= (pi/4) *d^2.

Velocity= (pi * d * N/60).

Head loss= (friction * length * velocity^2)/(2 * g * d).

= (f * length * (pi * d * N/60) ^2)/(2 * g * d).

Assume f, length and N are constant.

Head loss proportional to diameter.

Power = constant * d^4.

Anurag Adhikary said:   1 decade ago
There are so much of answers if we look into this from different laws and formulas. What answer should we choose in the exams?

Is someone there to give the most appropriate answer?


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