Mechanical Engineering - Hydraulic Machines - Discussion

6. 

Discharge of a centrifugal pump is

[A]. directly proportional to diameter of its impeller
[B]. inversely proportional to diameter of its impeller
[C]. directly proportional to (diameter)2 of its impeller
[D]. inversely proportional to (diameter)2 of its impeller

Answer: Option C

Explanation:

Discharge of a centrifugal pump is directly proportional to (Diameter)^2 of its impeller.

Head of a centrifugal pump is directly proportional to (Diameter)^2 of its impeller.

Power Developed of a centrifugal pump is directly proportional to (Diameter)^4 of its impeller.


Sushil said: (Nov 2, 2013)  
Discharge of centrifugal pump is given by Q = (pi)(D2)(B2)(Vf2).

As per above equation option (A) is correct.

Rahul said: (Nov 7, 2013)  
Discharge of centrifugal pump is Q = area* velocity of flow.

Q = (pi)(D1)(B1)(VF1) = (PI)(D2)(B2)(VF2).

Where B1 and B2 are width of impeller at inlet and outlet and B1 and B2 are diameter of impeller at inlet and outlet and VF1 and VF2 are velocity of flow at inlet and outlet.

Afrasiyab said: (May 26, 2015)  
Directly proportional to square of diameter.

Radhika said: (Aug 1, 2015)  
Directly proportional to diameter of its impeller. A is the correct answer.

Harry said: (Apr 28, 2016)  
As per Affinity Laws:

Speed is constant,

Q1/Q2 = (D1/D2)^3.

So, the answer is Discharge is inversely proportional to the cube of the diameter.

Anurag Adhikary said: (Jul 2, 2016)  
Correct the answers, it should be option A.

Kartheek said: (Jul 16, 2016)  
Discharge in centrifugal pump (Q) = pi * D * b * v.

where D = dia of the impeller at the inlet,
b = width of the impeller at the inlet
v = velocity of flow at the inlet.

So, according to the formula, discharge is directly proportional to Diameter of the impeller.

Faisal Mumtaz said: (Aug 19, 2016)  
Directly proportional to diameter so, option A is correct.

Honey said: (Aug 31, 2016)  
I think, All the options are not satisfied. The correct answer will be directly proportional to the cube of the diameter of vanes.

Smith said: (Oct 11, 2016)  
The discharge flow rate of a centrifugal pump is directly proportional to diameter. Discharge head is directly proportional to the square of the diameter. And power is directly proportional to the cube of the diameter. You can understand all this with the help of affinity laws.

Jwala said: (Nov 2, 2016)  
The correct answer should be A.

Hemant said: (Nov 10, 2016)  
We know that Q = pi * d * b * vf.

So that is directly proportional to d.

Sarat said: (Dec 22, 2016)  
Option A is the correct answer.

Parameswararao said: (Dec 23, 2016)  
Is directly proportional to the square of the diameter (refer R. K. Rajput textbook pg no. 1219).

Ashutosh said: (Apr 5, 2017)  
According to affinity law.

Flow or discharge is directly proportional to impeller diameter if the speed of the shaft is constant.

Patel Jigar K said: (Jun 16, 2017)  
The correct answer is A,
q = d.
h =d^2.
p = d^3.

Manikanta said: (Jun 20, 2017)  
Q = A.V.
A = π/4D2.
Q is directly proportional to d2.

Nabajyoti said: (Jun 25, 2017)  
It is Directly proportional to D.

Md Mina, said: (Jun 30, 2017)  
Yes, A is correct.

Daya said: (Jul 4, 2017)  
I think option A is right.

Venkat said: (Jul 22, 2017)  
The Answer is B.

Discharge of centrifugal pump is directly proportional to its (dia)^2.
Q = A * V,
Here A = π * D^2/4.

Shiva said: (Jul 26, 2017)  
As Q is directly proportional to B and D and B (width) is proportional to D. Therefore Q is directly proportional to D^2.

Suresh Shinde said: (Jul 28, 2017)  
Q/(N*D^3).

So, the correct answer is directly proportional to D^3.

Rishabh Singh said: (Aug 5, 2017)  
Affinity Law of a pump- Q is proportional to D.

Dhirendra Kumar said: (Aug 12, 2017)  
C is the right answer.

Pabitra said: (Sep 19, 2017)  
Q= 3.14 d b v = d^3 n so the correct answer will be d^3.

Pabitra said: (Sep 19, 2017)  
It should be diameter cube.

Muhammad Waqas said: (Oct 5, 2017)  
Q=πDb(V_f).

Where D=Diameter of impeller at inlet,
b=width of impeller at inlet,and
V_f=Velocity of flow at inlet.

Q=πDb(V_f).
Q=πDb(πDN/60).

Hence
Q is directly proportional to square of the diameter.

Kartheek said: (Nov 27, 2017)  
dicharge Q = pav, a= πd^2/4 so q is directly praporional to squre of diameter.

Ali said: (Jan 20, 2018)  
Answer C is correct.

Meet Patel said: (Feb 12, 2018)  
Q is directly proportional to D^3.

Bapi said: (Feb 13, 2018)  
Q/{N(D^3)}=constant.
So the correct answer is Q is directly proportional to cube of the diameter(D) of the impeller.

Saboor Khan Kamali said: (Mar 17, 2018)  
It is directly proportional to the square of the diameter.

Debashis said: (Apr 17, 2018)  
Option C is correct.

Debashis said: (Apr 19, 2018)  
Yes, option: C is correct.

Angari Abhinay said: (Apr 25, 2018)  
Discharge of centrifugal pump formula π*D*b*V,
Also, Discharge Head is directly proportional to D^2,
Power is Directly proportional to N^3.

Pal said: (Jun 12, 2018)  
Q= π*D*v*b and v=πdN/60.

So the right answer is proportional to d^2.

Deepak Rathva said: (Jun 22, 2018)  
Q= π x D x B x Vf.

Here, B also depends on D.
Vf depends on u means depends on DN,
So Q is directly proportional to D^3,
So all options are wrong.

Hemanth G said: (Jul 29, 2018)  
Here the discharge is asked,

I believe discharge refers to the outlet of the centrifugal compressor so

Q= π* D*B*Vf2 is the formula, that means A-option is the correct one to be chosen.

Utsav said: (Nov 25, 2018)  
No, the Discharge of a centrifugal pump is Directly proportional to Impeller diameter.

You can refer to below-given affinity laws.

Q1/Q2 = D1/D2.
H1/H2 = (D1/D2)^2,
P1/P2 = (D1/D2)^3.

Q Indicates Flow that is discharged,
H Indicates Head,
P Indicates Power.

Sekhar Mullapudi said: (Feb 28, 2019)  
The discharge flow rate is directly proportional to its diameter.

But here the question is an only discharge of centrifugal pump; So the answer is "directly proportional to the square of the diameter".

So, the correct option C is correct.

Biswajit Das said: (Jul 5, 2019)  
Option C is correct.
That Q= π D b Vf.
Anyhow Vf is related to V and V is related to u and u =π D N /60.
So, Q is directly proportional to D^2.

Engr Aamir said: (Oct 17, 2019)  
If Q=Av then Q is directly or inversely proportional?

Prithvi Singh said: (Jan 9, 2020)  
Q is directly proportional to D^3.

Fouziahussain said: (Feb 23, 2020)  
Q=(pi)DbV.

D=Diameter of impeller.
B =Width.
V= Velocity of flow.

Hrushi Nikam said: (May 1, 2020)  
When we calculate for specific speed we take the assumption of B being proportional to Diameter. So, option C is correct.

Shaik Murtuza said: (Dec 12, 2020)  
Option A is the correct answer.

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