# Flow rate in a pump

1. Jun 13, 2012

### hamshie.k

two tanks were placed. tank one at a higher level and other(tank 2) at lower level. But in tank 2 a pump of flow rate Q ml/min is affixed.what is the flow rate in tank 2. Same as Q /min???

2. Jun 13, 2012

### tiny-tim

welcome to pf!

hi hamshie.k! welcome to pf!
??

what exactly is the whole question?

3. Jun 13, 2012

### hamshie.k

tank 1 is placed above the level of tank 2. the water flows into tank 2 by the gravitational force from tank 1. But from thank 2 a pump is fixed to suck the water and again pump it into the tank 1.

the question is whether the tank 2 will have the same flow rate of the pump, at the top surface of the tank??

4. Jun 13, 2012

### tiny-tim

ahh!

ok, tell us what you think, and why, and then we'll comment!

5. Jun 13, 2012

### hamshie.k

A pump is placed in the top level surface of the tank 2. at a suction end . delivered to tank 1

6. Jun 13, 2012

### tiny-tim

(yes, i know, but) tell us what you think the answer is

7. Jun 13, 2012

### hamshie.k

same as the flow rate of the pump. i need that condition

8. Jun 13, 2012

### tiny-tim

correct

but why? (eg, is anything conserved, ie the same?)

9. Jun 13, 2012

### hamshie.k

No external force applied

10. Jun 13, 2012

### tiny-tim

forget the physics, just look at the material …

the total amount of water is the same (W1 + W2 = constant),

so W1' + W2' = 0

11. Jun 13, 2012

### Avis

Is it not possible that the pump in T2 can pump the water to T1 faster then T1 flows into T2?

12. Jun 13, 2012

### tiny-tim

if it's a closed system, where all the water has to be either in T1 or in T2 (or in the pipe between them, which we can assume is always full),

then the water lost by T2 has to equal the water gained by T1

13. Jun 13, 2012

### Avis

Fair, I was thinking in a more practical way.

14. Jun 13, 2012

### Travis_King

Maybe I'm thinking about this all wrong, but if you let water drain from T1 through a 3" hose and have a pump in T2 with a 1/8" discharge line back to T1, you will not have equal flow through the tanks. They may eventually reach a level of system equillibrium, but the flow rates need not be the same...If the pump is at the surface of the water and drawing from only the head (water level) in T2, then your flow rate will be based on the pump characteristics, not the flow through the gravity line.

Unless you mean tank T2 is fully filled, then obviously the only amount of water that could flow "into" it would be the amount that is flowing "out" to T1.

15. Jun 15, 2012

### hamshie.k

Please anyone help me . how i should start calculations for these kind of problems.

1. gravity flow from tank one to tank 2(i am planning to analyse for the tank placed below the level of tank 1 and also for the same level tanks)

2. pump calculations from tank 2 to tank 1

I dont know how to start the problem??

whether i should start from friction losses and benoulli eqn.
i have the flow rate of the pump(peristaltic pump). please guide me what are the calculations i need regarding this??