Calculating Maximum Pump Height for Given Flow Velocity | Pipe Friction Ignored

In summary, the conversation discusses the parameters and calculations for determining the maximum flow rate and velocity of a pump, as well as the inclusion of frictional effects and static head in the calculations. The equation used is a variation of Bernoulli's equation and can also be used to draw the system curve and determine the operating point. The maximum head for 0 flow is found to be 3.02m and the equation for the maximum flow rate is given as H(static) = 3.02 - (1 * 0.0002^2 (m^3/s)).
  • #1
skaboy607
108
0
Hi

I have a pump which for 0 head will provide a max flow of 12 l/min (0.0002 m^3/s). For the piping I am using (3/8"), by my calculations this gives a theoretical MAX mass flow rate of 0.2 m/s and a MAX velocity of 2.8 m/s.

As i understand it, these values are not taking into account (1) frictional effects in the piping and (2) static head involved in raising the fluid.

Ignoring the frictional effects in the piping for now, how would I calculate the max height this pump could pump water for a given flow velocity, say 1.5 m/s.

I'm sure it is Bernoulli's but there seems to be too many variables. I don't have access to the performance curves of the pump.

Thanks for your help.
 
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  • #2
Hm = Hst + losses
losses is defined as constant * Q^2
and u have Q = 12 L/S
AND d = 3/7 " so sub in this
o.8 * f * L * Q2/gD^5 you will find it a very small term because Q is small
so finally u can consider that H pump = H st + 3 or 4 meters
but H static should be taken into considerations
 
  • #3
Hi

Thanks for the reply. Can you elaborate on this please. I don't understand some of what you have done.

Is Hm=Total head, Hst=Static head (elevation head) and losses=frictional effects

Losses (frictional effects) defined as a constant * Q^2

Is this correct? I'm with you up until this point.

The equation you've written now, is it some varation of Darcy's. Can you explain please.

Thanks
 
  • #4
yes man its correct and its a form of bernoulis equation
 
  • #5
and remeber also this equation is also used to draw the system curve of the pumping system and the intersection between it and the pump curve is the operating point
 
  • #6
maxx_payne said:
and remeber also this equation is also used to draw the system curve of the pumping system and the intersection between it and the pump curve is the operating point

ok...so I also found out that the max head for 0 flow is 4.3 psi (3.02m) so I can write hw=H (static) + constant*Q^2.

Therefore for the max flow rate the pump can produce (12 l/min) and assuming frictional loss in pipe is constant at 1 for now, I can write:

H(static)=3.02-(1*0.0002^2 (m^3/s))=3.0196m

Is this right?
 

1. What is the purpose of determining pump height?

The purpose of determining pump height is to determine the vertical distance that a pump can effectively move water or other fluids. This is important in selecting the right pump for a given application and ensuring its efficiency.

2. How is pump height measured?

Pump height is typically measured in feet or meters from the centerline of the pump to the highest point of discharge or to the surface of the liquid being pumped. It can also be measured in terms of pressure, such as pounds per square inch (PSI) or bar.

3. What factors affect pump height?

The factors that can affect pump height include the type and design of the pump, the speed at which it is operated, the density and viscosity of the fluid being pumped, and the length and diameter of the discharge pipe. Other factors may include the elevation and atmospheric pressure at the pump site.

4. How do you calculate pump height?

Pump height can be calculated by adding the static head (vertical distance from pump centerline to the highest point of discharge) to the friction head (resistance caused by fluid flow through piping). This can be done using a pump performance curve or by using pump equations that take into account factors such as flow rate, pump efficiency, and fluid properties.

5. Why is it important to accurately determine pump height?

Accurately determining pump height is important because it ensures that the pump is capable of meeting the required flow and pressure requirements for a given application. It also helps to determine the proper pump size and type, which can impact the overall cost and efficiency of the pumping system. Additionally, knowing the pump height can help identify potential issues or inefficiencies in the system and allow for proper troubleshooting and maintenance.

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